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1.
Potato plants (Solanum tuberosum L.) were grown at differentair and soil temperatures to determine the effects of high-temperaturestress on root, tuber, and shoot growth. Cooling the soil (1727C) at high air temperatures (3040 C) relieved noneof the visible symptoms of heat stress on shoot growth; norwas the degree of induction to tuberize in leaves increased,as reflected in tuberization of leaf-bud cuttings. Heating thesoil (2735 C) at cool (1727 C) air temperatureshad no apparent detrimental effect on shoot growth or inductionof leaves to tuberize. However, in each case hot soil largelyeliminated tuber development. In one experiment stolons grewup out of the hot soil and formed aerial tubers upon reachingthe cool air. When leaf-bud cuttings from induced plants wereused as a model system, high soil temperatures inhibited tuberdevelopment from the buried leaf buds, in the absence of anyroot growth. Apparently the induction of leaves to tuberizeis affected principally by air rather than soil temperature,but expression of the signal to tuberize can be blocked by highsoil temperature. Solanum tuberosum L., potato, temperature stress, soil temperature, tuberization 相似文献
2.
Phenological modifications in plants by various edaphic factors 总被引:1,自引:0,他引:1
F. E. Wielgolaski 《International journal of biometeorology》2001,45(4):196-202
Various mechanical, chemical and physical soil analyses were carried out, in addition to weather observations, for 3 years
at several sites along an oceanic-continental gradient in a fjord district in western Norway. All the environmental factors
observed were correlated with the spring and a few late-season phenophases of many native and cultivated woody plants and
some herbs by simple, linear correlations and by stepwise multiple and partial analyses. Different techniques were used to
try and eliminate many intercorrelations between various environmental factors.
As expected, air temperature measurements in nearly all analyses from these temperate region districts gave the most significant
correlations with the phenology of the plants, the temperature during the night generally being the most important in mainly
vegetative periods, e.g. to leaf bud break in spring, and the temperature during the day affecting the more generative phases,
such as the period between leaf bud break and flowering. The other environmental factors, however, showed strong variation
in correlation significance among the various species studied and also with different phenophases of the same species. Various
hypotheses are put forward to explain such variation. Air humidity (including precipitation) and /or soil moisture (including
intercorrelated parameters, e.g. soil grain size and bulk density) were relatively often found to be of importance. In the
stepwise multiple analyses for leaf bud break of the birch (Betula pubescens), for instance, the amount of precipitation was the second factor to enter the analyses by a positive correlation with the
developmental rate, after the most important factor, the night temperature. Positive correlations with a high clay content
and bulk density in the soil indicated that high soil moisture is also favourable for early bud break in the birch. Other
phenophases that seemed to be favoured by a good water supply were leaf bud break of the bird cherry (Prunus padus) and rowan (Sorbus aucuparia), and flowering of the hazel (Corylus avellana), common lilac (Syringa vulgaris), plum (’Victoria’) and currant (’Red Dutch’) and also, to some degree, the goat willow (Salix caprea). The amount of ions (P, K, Mg and Ca) often showed negative correlations with the developmental rate, particularly of earlier
phenophases of both native and cultivated plants (except for the apple ’Gravenstein’ and pear ’Moltke’), possibly, indicating
that a high nutrient level delayed plant development. A similar explanation might be given for the observation that high pH
in the soil often seemed to delay plant development (leaf bud break of Betula, Sorbus, Syringa and plum, and flowering of Corylus, bluebell (Campanula rotundifolia) and red currant). According to the analyses there seemed to be a tendency for plants that are particularly dependent on
warm weather for leaf bud break, e.g. the ash (Fraxinus excelsior), and flowering, e.g. Prunus, pear, apple and, to some degree, the raspberry (’Preussen’), to be less dependent on other environmental factors for their
development. For instance, if there were any effects of water for these plants, they were negative for moisture and soil factors
intercorrelated with water.
Received: 25 October 2000 / Revised: 9 May 2001 / Accepted: 24 May 2001 相似文献
3.
Rose plants (Rosa hybrida ‘Sonia’=‘Sweet Promise’) were grown in heated (minimum night temperature 17°C), and unheated greenhouses with or without
root heating to 21°C. These trials covered 6 growth cycles extending over two winter seasons. In the heated greenhouse, root
heating did not increase yield, flower quality or plant development. In the unheated greenhouse, root-heated plants grew as
well as those in the air-heated greenhouse as long as the air temperature did not fall below 6°C. When minimum night temperatures
fell below 6°C, growth, yield and quality were reduced, irrespective of root temperature.
Daytime plant water relations were studied in plants growing at 6 different root temperatures in the unheated greenhouse.
Leaf resistance to water diffusion was lowest at optimal root temperature. Total leaf water potential was not significantly
affected by root temperature. 相似文献
4.
- The woody shoots of young saplings of Fraxinus.excelsior andAcer Pseudo-platanus in pots were subjected to continuous coolingto about 2° C. during the growth season, with the resultthat radial growth was almost completely inhibited throughoutthe woody stem.
- The chilling did not adversely affect extensiongrowth exceptthat it was later in commencement and proceededmore slowly.
- If the temperature around the stem is loweredfrom 2° C.to 0° C., water conduction is cut down tosuch an extentas to cause wilting of the leafy shoots; turgidityis recoveredwhen the temperature is again raised to 2°C.
- This wilting effect is discussed particularly in relationtothe part played by living cells in the upward movement ofwaterin the wood.
5.
To study the reliabiliity of formulas for calculating mean skin temperature (T
sk), values were computed by 18 different techniques and were compared with the mean of 10,841 skin temperatures measured by
infrared thermography. One hundred whole-body infrared thermograms were scanned in ten resting males while changing the air
temperature from 40° C to 4° C. Local, regional average and mean skin temperatures were obtained using an image processing
system. The agreement frequency, defined as the percentage of the calculated T
sk values which agreed with the corresponding infrared thermographic T
sk within ±0.2° C, ranged for with the various formulas from 7% to 80%. In many sites, the local skin temperature did not coincide
with the regional average skin temperature. When the local skin temperatures which showed the highest percentage similarity
to the regional average skin temperature within ±0.4° C were applied to the formula, the agreement frequency was markedly
improved for all formulas. However, the agreement frequency was not affected by changing the weighting factors from specific
constants to individually measured values of regional surface area. By applying the physiologically reliable accuracy range
of ±0.2° C in the moderate and ±0.4° C in the cool condition, agreement frequencies of at least 95% were observed in formulas
involving seven or more skin temperature measurement sites, including the hand and foot. We conclude that calculation of a
reliable mean skin temperature must involve more than seven skin temperature measurement sites regardless of ambient temperature.
Optimal sites for skin temperature measurement are proposed for various formulas.
Received: 2 December 1996 / Accepted: 25 June 1997 相似文献
6.
Two experiments were conducted to assess the response of cauliflower (Brassica oleracea L. var. botrytis) cv. “Nautilus” F1 hybrid to different constant temperatures after curd initiation by keeping the plants in six different
temperature-controlled glasshouse compartments with heating set point temperatures of 6, 10, 14, 18, 22, and 26 °C (±4 °C)
at the School of Plant Sciences, The University of Reading, UK during winter 1998–1999 and summer 1999. Many of the growth
parameters increased with increasing mean growing temperature up to an optimum temperature and then declined with further
increases in temperature. Therefore, cauliflower’s growth and development after curd initiation could be resolved into linear
or curvilinear function of effective temperatures calculated with optimum temperatures between 19 and 23 °C. It is suggested
that future warmer climates will be beneficial for winter cauliflower production rather than summer cauliflower production. 相似文献
7.
Tor Myking 《Trees - Structure and Function》1998,12(4):224-229
Respiration in vegetative buds of mature Betula pendula, Alnus glutinosa and Prunus padus trees was measured monthly at 15°C from mid-October 1996 to natural outdoor budburst in April 1997. In B. pendula the effect of bud water content on respiration was also estimated (December–April) by artificial imbibition of buds for 24
h prior to measurement of respiration. For estimation of corresponding bud dormancy status, batches of twigs were forced at
identical monthly intervals at 15°C in long days (24 h), and budburst recorded. In all species dormancy was deepest when the
leaves were shed in October, and dormancy was first alleviated in P. padus followed by B. pendula and A. glutinosa. However, bud respiration capacity was not related to dormancy release as it decreased in all species from October to November
and displayed no notable increase until February in P. padus, March in B. pendula and April in A. glutinosa, after completion of dormancy release. Rather, increase in respiration coincided with growth resumption prior to budburst.
Artificial imbibition of B. pendula buds increased the water content by approximately 10% (FW) and induced a doubling of the respiration rate (December–February).
Moreover, the seasonal variation in bud water content (October–April) explained 94% of the variation in respiration in B. pendula and P. padus, and 84% in A. glutinosa. These observations suggest an important role of water content for respiration. During a cold period from mid-December to
mid-January with mean temperature of –9.7°C dormancy release was arrested in P. padus, and to some degree in A. glutinosa, whereas dormancy release progressed normally in B. pendula. This indicates species differences in lower critical temperatures for dormancy release.
Received: 30 June 1997 / Acceped: 1 October 1997 相似文献
8.
Helmut Bauer Monika Nagele Monica Comploj Verena Galler Monika Mair Edith Unterpertinger 《Physiologia plantarum》1994,91(3):403-412
The objective of this study was to compare the photosynthetic changes during cold acclimation in various plant types able to acquire different degrees of freezing tolerance. Four herbaceous and six woody plants were hardened under natural or artificial conditions and – after determination of their frost resistance (LT50) – the net photosynthetic rate at an ambient CO2 of 33 Pa (Pn33), the dependencies of Pn to light and to CO2 and the room temperature chlorophyll a fluorescence were recorded under optimal conditions. Herbaceous plants acquired freezing tolerances to temperatures between ?10 and ?15°C when hardened at temperatures around 0°C. Most leaves fully developed prior to frost hardening exhibited typical symptoms of senescence after frost hardening. In non-senescing leaves Pn33 was reduced by 15 to 50% mainly due to a reduced stomatal conductance. After hardening at temperatures around ?10°C Brassica survived down to ?24°C, but Pn33 was almost abolished as a result of disturbances in the chloroplasts. After transferring the plants to 20/15°C Pn33 recovered completely within a few days. Woody plants hardened at temperatures around 0°C tolerated – 15 to ?36°C: Pn33 was reduced by 25 to 60% and hardly recovered at 20/15°C. Hardening at ?10°C induced a tolerance of ?32 to 80°C. Pn33 was almost totally blocked, but at 20/15°C it returned to the values of the plants hardened at 0°C within a few days. In woody plants disturbances were invariably localized in the chloroplasts. Thus, conifers, and especially Pinus cembra, can survive much lower temperatures than herbaceous plants and, at the same level of freezing tolerance, exhibit appreciably less restriction in relative Pn33. 相似文献
9.
Acclimation of chlorophyll biosynthetic reactions to temperature stress in cucumber (Cucumis sativus L.) 总被引:1,自引:0,他引:1
The adaptive responses of the greening process of plants to temperature stress were studied in cucumber (Cucumis sativus L. cv. Poinsette) seedlings grown at ambient (25 °C), low (7 °C) and high (42 °C) temperatures. Plastids isolated from these
seedlings were incubated at different temperatures and the net syntheses of various tetrapyrroles were monitored. In plastids
isolated from control seedlings grown at 25 °C, the optimum temperature for synthesis of Mg-protoporphyrin IX monoester or
protochlorophyllide was 35 °C. Temperature maxima for Mg-protoporphyrin IX monoester and protochlorophyllide syntheses were
shifted to 30 °C in chill-stressed seedlings. The net synthesis of total tetrapyrroles was severely reduced in heat-stressed
seedlings and the optimum temperature for Mg-protoporphyrin IX monoester or protochlorophyllide synthesis shifted slightly
towards higher temperatures, i.e. a broader peak was observed. To further study the temperature acclimation of seedlings with
respect to the greening process, tetrapyrrole biosynthesis was monitored at 25 °C after pre-heating the plastids (28–70 °C)
isolated from control, chill- and heat-stressed seedlings. In comparison to 28 °C-pre-heated plastids the percent inhibition
of protochlorophyllide synthesis in 40 °C-pre-heated plastids was higher than for the control (25 °C-grown) in chill-stressed
seedlings and lower than for the control in heat-stressed seedlings. Maximum synthesis of total tetrapyrroles and protoporphyrin
IX was observed when chloroplasts were heated at 50 °C, which was probably due to heat-induced activation of the enzymes involved
in protoporphyrin IX synthesis. Prominent shoulders towards lower or higher temperatures were seen in chill-stressed or heat-stressed
seedlings, respectively. The shift in optimum temperature for tetrapyrrole biosynthesis in chill- and heat-stressed seedlings
was probably due to acclimation of membranes possibly undergoing desaturation or saturation of membrane lipids. Proteins synthesized
in response to temperature-stress may also play an important role in conferring stress-tolerance in plants.
Received: 8 October 1998 / Accepted: 19 November 1998 相似文献
10.
Intact leaves of kiwifruit (Actinidia deliciosa (A. Chev.) C.F. Liang et A.R. Ferguson) from plants grown in a range of controlled temperatures from 15/10 to 30/25°C were
exposed to a photon flux density (PFD) of 1500 μmol·m−2·s−1 at leaf temperatures between 10 and 25°C. Photoinhibition and recovery were followed at the same temperatures and at a PFD
of 20 μmol·m−2·s−1, by measuring chlorophyll fluorescence at 77 K and 692 nm, by measuring the photon yield of photosynthetic O2 evolution and light-saturated net photosynthetic CO2 uptake. The growth of plants at low temperatures resulted in chronic photoinhibition as evident from reduced fluorescence
and photon yields. However, low-temperature-grown plants apparently had a higher capacity to dissipate excess excitation energy
than leaves from plants grown at high temperatures. Induced photoinhibition, from exposure to a PFD above that during growth,
was less severe in low-temperature-grown plants, particularly at high exposure temperatures. Net changes in the instantaneous
fluorescence,F
0, indicated that little or no photoinhibition occurred when low-temperature-grown plants were exposed to high-light at high
temperatures. In contrast, high-temperature-grown plants were highly susceptible to photoinhibitory damage at all exposure
temperatures. These data indicate acclimation in photosynthesis and changes in the capacity to dissipate excess excitation
energy occurred in kiwifruit leaves with changes in growth temperature. Both processes contributed to changes in susceptibility
to photoinhibition at the different growth temperatures. However, growth temperature also affected the capacity for recovery,
with leaves from plants grown at low temperatures having moderate rates of recovery at low temperatures compared with leaves
from plants grown at high temperatures which had negligible recovery. This also contributed to the reduced susceptibility
to photoinhibition in low-temperature-grown plants. However, extreme photoinhibition resulted in severe reductions in the
efficiency and capacity for photosynthesis. 相似文献
11.
Yongshuo H. Fu Xiaojun Geng Fanghua Hao Yann Vitasse Constantin M. Zohner Xuan Zhang Xuancheng Zhou Guodong Yin Josep Peuelas Shilong Piao Ivan A. Janssens 《Global Change Biology》2019,25(12):4282-4290
Temperature during a particular period prior to spring leaf‐out, the temperature‐relevant period (TRP), is a strong determinant of the leaf‐out date in temperate‐zone trees. Climatic warming has substantially advanced leaf‐out dates in temperate biomes worldwide, but its effect on the beginning and length of the TRP has not yet been explored, despite its direct relevance for phenology modeling. Using 1,551 species–site combinations of long‐term (1951–2016) in situ observations on six tree species (namely, Aesculus hippocastanum, Alnus glutinosa, Betula pendula, Fagus sylvatica, Fraxinus excelsior, and Quercus robur) in central Europe, we found that the advancing leaf‐out was accompanied by a shortening of the TRP. On average across all species and sites, the length of the TRP significantly decreased by 23% (p < .05), from 60 ± 4 days during 1951–1965 to 47 ± 4 days during 2002–2016. Importantly, the average start date of the TRP did not vary significantly over the study period (March 2–5, DOY = 61–64), which could be explained by sufficient chilling over the study period in the regions considered. The advanced leaf‐out date with unchanged beginning of the TRP can be explained by the faster accumulation of the required heat due to climatic warming, which overcompensated for the retarding effect of shortening daylength on bud development. This study shows that climate warming has not yet affected the mean TRP starting date in the study region, implying that phenology modules in global land surface models might be reliable assuming a fixed TRP starting date at least for the temperate central Europe. Field warming experiments do, however, remain necessary to test to what extent the length of TRP will continue to shorten and whether the starting date will remain stable under future climate conditions. 相似文献
12.
The effects of temperature on photosynthesis of a rosette plant growing at ground level, Acaena cylindrostachya R. et P., and an herb that grows 20–50 cm above ground level, Senecio formosus H.B.K., were studied along an altitudinal gradient in the Venezuelan Andes. These species were chosen in order to determine
– in the field and in the laboratory – how differences in leaf temperature, determined by plant form and microenvironmental
conditions, affect their photosynthetic capacity. CO2 assimilation rates (A) for both species decreased with increasing altitude. For Acaena leaves at 2900 m, A reached maximum values above 9 μmol m−2 s−1, nearly twice as high as maximum A found at 3550 m (5.2) or at 4200 m (3.9). For Senecio leaves, maximum rates of CO2 uptake were 7.5, 5.8 and 3.6 μmol m−2 s−1 for plants at 2900, 3550 and 4200 m, respectively. Net photosynthesis-leaf temperature relations showed differences in optimum
temperature for photosynthesis (A
o.t.) for both species along the altitudinal gradient. Acaena showed similar A
o.t. for the two lower altitudes, with 19.1°C at 2900 m and 19.6°C at 3550 m, while it increased to 21.7°C at 4200 m. Maximum
A for this species at each altitude was similar, between 5.5 and 6.0 μmol m−2 s−1. For the taller Senecio, A
o.t. was more closely related to air temperatures and decreased from 21.7°C at 2900 m, to 19.7°C at 3550 m and 15.5°C at 4200 m.
In this species, maximum A was lower with increasing altitude (from 6.0 at 2900 m to 3.5 μmol m−2 s−1 at 4200 m). High temperature compensation points for Acaena were similar at the three altitudes, c. 35°C, but varied in Senecio from 37°C at 2900 m, to 39°C at 3550 m and 28°C at 4200 m. Our results show how photosynthetic characteristics change along
the altitudinal gradient for two morphologically contrasting species influenced by soil or air temperatures.
Received: 5 July 1997 / Accepted: 25 October 1997 相似文献
13.
Notonecta unifasciata Guerin eggs maintained at different stages of embryonic development in water at variable temperatures (2.2–25.6 °C) and for
periods of 4–12 weeks revealed maximum viability (>80 %) at the highest temperature. However, optimum nondevelopmental viability
was at 14.4 °C with eight-day-old embryos (>35 %). Short term (4 weeks) storage at 14.4 °C significantly increased egg viability.
Survival was poor (<20 %) at the 2 lowest temperatures. Eggs held at 14.4 °C for 12 weeks and sustainingca. 50 % mortality, may be a practical procedure for biological control.
相似文献
14.
Polar-desert plants experience low average air temperatures during their short growing season (4–8 °C mean July temperature).
In addition, low availability of inorganic nitrogen in the soil may also limit plant growth. Our goals were to elucidate which
N sources can be acquired by polar-desert plants, and how growth and N-uptake are affected by low growth temperatures. We
compared rates of N-uptake and increases in mass and leaf area of two polar-desert species (Cerastium alpinum L. and Saxifraga caespitosa L.) over a period of 3 weeks when grown at two temperatures (6 °C vs. 15 °C) and supplied with either glycine, NH4
+ or NO3
−. At 15 °C, plants at least doubled their leaf area, whereas there was no change in leaf area at 6 °C. Measured mean N-uptake
rates varied between 0.5 nmol g−1 root DM s−1 on glycine at 15 °C and 7.5 nmol g−1 root DM s−1 on NH4
+ at 15 °C. Uptake rates based upon increases in mass and tissue N concentrations showed that plants had a lower N-uptake rate
at 6 °C, regardless of N source or species. We conclude that these polar-desert plants can use all three N sources to increase
their leaf area and support flowering when grown at 15 °C. Based upon short-term (8 h) uptake experiments, we also conclude
that the short-term capacity to take up inorganic or organic N is not reduced by low temperature (6 °C). However, net N-uptake
integrated over a three-week period is severely reduced at 6 °C.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
15.
The 8 days old seedlings of pea (cv. Ilowiecki) and maize (cv. Alma F1) were subjected to differentiated aeration conditions (control — with pore water tension about 15 kPa and flooded
treatment) for 12 days at three soil temperatures (7, 15 and 25 °C). The shoots were grown at 25 °C while the soil temperature
was differentiated by keeping the cylinders with the soil in thermostated water bath of the appropriate temperature.
Lowering the root temperature with respect to the shoot temperature caused under control (oxic) conditions a decrease of the
root penetration depth, their mass and porosity as well as a decrease of shoot height, their mass and chlorophyll content;
the changes being more pronounced in maize as compared to the pea plants. Flooding the soil diminished the effect of temperature
on the investigated parameters; the temperature effect remaining significant only in the case of shoot biomass and root porosity
of pea plants. Root porosity of pea plants ranged from 2 to 4 % and that of maize plants — from 4 to 6 % of the root volume.
Flooding the soil caused an increase in the root porosity of the pea plants in the entire temperature range and in maize roots
at lower temperatures by about 1 % of the root volume. Flooding the soil caused a decrease of root mass and penetration depth
as well as a decrease of plant height, biomass and leaf chlorophyll content. 相似文献
16.
The predominant emphasis on harmful effects of environmental stresses on growth of woody plants has obscured some very beneficial
effects of such stresses. Slowly increasing stresses may induce physiological adjustment that protects plants from the growth
inhibition and/or injury that follow when environmental stresses are abruptly imposed. In addition, short exposures of woody
plants to extreme environmental conditions at critical times in their development often improve growth. Furthermore, maintaining
harvested seedlings and plant products at very low temperatures extends their longevity.
Drought tolerance: Seedlings previously exposed to water stress often undergo less inhibition of growth and other processes following transplanting
than do seedlings not previously exposed to such stress. Controlled wetting and drying cycles often promote early budset,
dormancy, and drought tolerance. In many species increased drought tolerance following such cycles is associated with osmotic
adjustment that involves accumulation of osmotically active substances. Maintenance of leaf turgor often is linked to osmotic
adjustment. A reduction in osmotic volume at full turgor also results in reduced osmotic potential, even in the absence of
solute accumulation. Changes in tissue elasticity may be important for turgor maintenance and drought tolerance of plants
that do not adjust osmotically.
Water deficits and nutrient deficiencies promote greater relative allocation of photosynthate to root growth, ultimately resulting
in plants that have higher root:shoot ratios and greater capacity to absorb water and minerals relative to the shoots that
must be supported.
At the molecular level, plants respond to water stress by synthesis of certain new proteins and increased levels of synthesis
of some proteins produced under well-watered conditions. Evidence has been obtained for enhanced synthesis under water stress
of water-channel proteins and other proteins that may protect membranes and other important macromolecules from damage and
denaturation as cells dehydrate.
Flood tolerance: Both artificial and natural flooding sometimes benefit woody plants. Flooding of orchard soils has been an essential management
practice for centuries to increase fruit yields and improve fruit quality. Also, annual advances and recessions of floods
are crucial for maintaining valuable riparian forests. Intermittent flooding protects bottomland forests by increasing groundwater
supplies, transporting sediments necessary for creating favorable seedbeds, and regulating decomposition of organic matter.
Major adaptations for flood tolerance of some woody plants include high capacity for producing adventitious roots that compensate
physiologically for decay of original roots under soil anaerobiosis, facilitation of oxygen uptake through stomata and newly
formed lenticels, and metabolic adjustments. Halophytes can adapt to saline water by salt tolerance, salt avoidance, or both.
Cold hardiness: Environmental stresses that inhibit plant growth, including low temperature, drought, short days, and combinations of these,
induce cold hardening and hardiness in many species. Cold hardiness develops in two stages: at temperatures between 10° and
20°C in the autumn, when carbohydrates and lipids accumulate; and at subsequent freezing temperatures. The sum of many biochemical
processes determines the degree of cold tolerance. Some of these processes are hormone dependent and induced by short days;
others that are linked to activity of enzyme systems are temperature dependent. Short days are important for development of
cold hardiness in species that set buds or respond strongly to photoperiod. Nursery managers often expose tree seedlings to
moderate water stress at or near the end of the growing season. This accelerates budset, induces early dormancy, and increases
cold hardiness.
Pollution tolerance: Absorption of gaseous air pollutants varies with resistance to flow along the pollutant’s diffusion path. Hence, the amount
of pollutant absorbed by leaves depends on stomatal aperture, stomatal size, and stomatal frequency. Pollution tolerance is
increased when drought, dry air, or flooding of soil close stomatal pores.
Heat tolerance: Exposure to sublethal high temperature can increase the thermotolerance of plants. Potential mechanisms of response include
synthesis of heat-shock proteins and isoprene and antioxidant production to protect the photosynthetic apparatus and cellular
metabolism.
Breaking of dormancy: Seed dormancy can be broken by cold or heat. Embryo dormancy is broken by prolonged exposure of most seeds to temperatures
of 1° to 15°C. The efficiency of treatment depends on interactions between temperature and seed moisture content. Germination
can be postponed by partially dehydrating seeds or altering the temperature during seed stratification. Seed-coat dormancy
can be broken by fires that rupture seed coats or melt seedcoat waxes, hence promoting water uptake. Seeds with both embryo
dormancy and seed-coat dormancy may require exposure to both high and low temperatures to break dormancy. Exposure to smoke
itself can also serve as a germination cue in breaking seed dormancy in some species.
Bud dormancy of temperate-zone trees is broken by winter cold. The specific chilling requirement varies widely with species
and genotype, type of bud (e.g., vegetative or floral bud), depth of dormancy, temperature, duration of chilling, stage of
plant development, and daylength. Interruption of a cold regime by high temperature may negate the effect of sustained chilling
or breaking of bud dormancy. Near-lethal heat stress may release buds from both endodormancy and ecodormancy.
Pollen shedding: Dehiscence of anthers and release of pollen result from dehydration of walls of anther sacs. Both seasonal and diurnal pollen
shedding are commonly associated with shrinkage and rupture of anther walls by low relative humidity. Pollen shedding typically
is maximal near midday (low relative humidity) and low at night (high relative humidity). Pollen shedding is low or negligible
during rainy periods.
Seed dispersal: Gymnosperm cones typically dehydrate before opening. The cones open and shed seeds because of differential shrinkage between
the adaxial and abaxial tissues of cone scales. Once opened, cones may close and reopen with changes in relative humidity.
Both dehydration and heat are necessary for seed dispersal from serotinous (late-to-open) cones. Seeds are stored in serotinous
cones because resinous bonds of scales prevent cone opening. After fire melts the resinous material, the cone scales can open
on drying. Fires also stimulate germination of seeds of some species. Some heath plants require fire to open their serotinous
follicles and shed seeds. Fire destroys the resin at the valves of follicles, and the valves then reflex to release the seeds.
Following fire the follicles of some species require alternate wetting and drying for efficient seed dispersal.
Stimulation of reproductive growth: Vegetative and reproductive growth of woody plants are negatively correlated. A heavy crop of fruits, cones, and seeds is
associated with reduced vegetative growth in the same or following year (or even years). Subjecting trees to drought during
early stages of fruit development to inhibit vegetative growth, followed by normal irrigation, sometimes favors reproductive
growth. Short periods of drought at critical times not only induce formation of flower buds but also break dormancy of flower
buds in some species. Water deficits may induce flowering directly or by inhibiting shoot flushing, thereby limiting the capacity
of young leaves to inhibit floral induction. Postharvest water stress often results in abundant return bloom over that in
well-irrigated plants. Fruit yields of some species are not reduced or are increased by withholding irrigation during the
period of shoot elongation. In several species, osmotic adjustment occurs during deficit irrigation. In other species, increased
fruit growth by imposed drought is not associated largely with osmotic adjustment and maintenance of leaf turgor.
Seedling storage: Tree seedlings typically are stored at temperatures just above or below freezing. Growth and survival of cold-stored seedlings
depend on such factors as: date of lifting from the nursery; species and genotype; storage temperature, humidity, and illumination;
duration of storage; and handling of planting stock after storage. Seedlings to be stored over winter should be lifted from
the nursery as late as possible. Dehydration of seedlings before, during, and after storage adversely affects growth of outplanted
seedlings. Long-term storage of seedlings may result in depletion of stored carbohydrates by respiration and decrease of root
growth potential. Although many seedlings are stored in darkness, a daily photoperiod during cold storage may stimulate subsequent
growth and increase survival of outplanted seedlings. For some species, rapid thawing may decrease respiratory consumption
of carbohydrates (over slowly thawed seedlings) and decrease development of molds.
Pollen storage: Preservation of pollen is necessary for insurance against poor flowering years, for gene conservation, and for physiological
and biochemical studies. Storage temperature and pollen moisture content largely determine longevity of stored pollen. Pollen
can be stored successfully for many years in deep freezers at temperatures near −15°C or in liquid nitrogen (−196°C). Cryopreservation
of pollen with a high moisture content is difficult because ice crystals may destroy the cells. Pollens of many species do
not survive at temperatures below −40°C if their moisture contents exceed 20–30%. Pollen generally is air dried, vacuum dried,
or freeze dried before it is stored. To preserve the germination capacity of stored pollen, rehydration at high humidity often
is necessary.
Seed storage: Seeds are routinely stored to provide a seed supply during years of poor seed production, to maintain genetic diversity,
and to breed plants. For a long time, seeds were classified as either orthodox (relatively long-lived, with capacity for dehydration
to very low moisture contents without losing viability) or recalcitrant (short-lived and requiring a high moisture content
for retention of viability). More recently, some seeds have been reclassified as suborthodox or intermediate because they
retain viability when carefully dried. True orthodox seeds are preserved much more easily than are nonorthodox seeds. Orthodox
seeds can be stored for a long time at temperatures between 2° and −20°C, with temperatures below −5°C preferable. Some orthodox
seeds have been stored at superlow temperatures, although temperatures of −40°, −70°, or −196°C have not been appreciably
better than −20°C for storage of seeds of a number of species. Only relatively short-term storage protocols have been developed
for nonorthodox seeds. These treatments typically extend seed viability to as much as a year. The methods often require cryopreservation
of excised embryos. Responses to cryopreservation of nonorthodox seeds or embryos vary with species and genotype, rate of
drying, use of cryoprotectants, rates of freezing and thawing, and rate of rehydration.
Fruit storage: Storing fruits at low temperatures above freezing, increasing the CO2 concentration, and lowering the O2 concentration of fruit storage delays senescence of fruits and prolongs their life. Fruits continue to senesce and decay
while in storage and become increasingly susceptible to diseases. Both temperate-zone and tropical fruits may develop chilling
injury characterized by lesions, internal discoloration, greater susceptibility to decay, and shortened storage life. Chilling
injury can be controlled by chemicals, temperature conditioning, and intermittent warming during storage. Stored fruits may
become increasingly susceptible to disease organisms. Fruit diseases can be controlled by cold, which inhibits growth of microorganisms
and maintains host resistance. Exposure of fruits to high CO2 and low O2 during storage directly suppresses disease-causing fungi. Pathogens also can be controlled by exposing fruits to heat before,
during, and after storage. Scald that often develops during low-temperature storage can be controlled by chemicals and by
heat treatments. 相似文献
17.
Three species of Arctic to cold-temperate amphi-Atlantic algae, all occurring also in the North Pacific, were tested for growth
and/or survival at temperatures of −20 to 30°C. When isolates from both western and eastern Atlantic shores were tested side-by-side,
it was found that thermal ecotypes may occur in such Arctic algae.Chaetomorpha melagonium was the most eurythermal of the 3 species. Isolates of this alga were alike in temperature tolerance and growth rate but
Icelandic plants were more sensitive to the lethal temperature of 25°C than were more southerly isolates from both east and
west. With regard toDevaleraea ramentacea, one Canadian isolate grew extraordinarily well at −2 and 0°C, and all tolerated temperatures 2–3°C higher than the lethal
limit (18–20°C) of isolates from Europe. ConcerningPhycodrys rubens, both eastern and western isolates died at 20°C but European plants tolerated the lethal high temperature longer, were more
sensitive to freezing, and attained more rapid growth at optimal temperatures. The intertidal species,C. melagonium andD. ramentacea, both survived freezing at −5 and −20°C, at least for short time periods.C. melagonium was more susceptible thanD. ramentacea to desiccation. Patterns of thermal tolerance may provide insight into the evolutionary history of seaweed species. 相似文献
18.
Crepinšek Z Stampar F Kajfež-Bogataj L Solar A 《International journal of biometeorology》2012,56(4):681-694
Knowledge of plant–weather relationships can improve crop management, resulting in higher quality and more stable crop yields. The annual timing of spring phenophases in mid-latitudes is largely a response to temperature, and reflects the thermal conditions of previous months. The effect of air temperature on the variability of hazelnut (Corylus avellana L.) phenophases (leafing, flowering) was investigated. Meteorological and phenological data for five cultivars were analysed over the periods 1969–1979 (P1) and 1994–2007 (P2) in Maribor, Slovenia. Phenological data series were correlated strongly to the temperature of the preceding months (R 2: 0.64–0.98) and better correlated to daily maximum and mean temperatures than to daily minimum temperatures. About 75% of phenophases displayed a tendency towards earlier appearance and a shorter flowering duration during P2, which could be explained by the significant temperature changes (+0.3°C/decade) from December to April between 1969 and 2007. An increase in air temperature of 1°C caused an acceleration in leafing by 2.5–3.9 days, with flowering showing higher sensitivity since a 1°C increase promoted male flowering by 7.0–8.8 days and female flowering by 6.3–8.9 days. The average rate of phenological change per degree of warming (days earlier per +1°C) did not differ significantly between P1 and P2. An estimation of chilling accumulation under field conditions during 1993–2009, between 1 November and 28 February, showed that all four of these months contributed approximately similar amounts of accumulated chilling units. The growing degree days (GDD) to flowering were calculated by an estimated base temperature of 2°C and 1 January as a starting date, given the most accurate calculations. In general, thermal requirements were greater in P2 than in P1, although this difference was not significant. Longer-time series data extended to other agricultural and wild plants would be helpful in tracking possible future changes in phenological responses to local climate. 相似文献
19.
The success of P. juliflora, an evergreen woody species has been largely attributed to temperature acclimation and stomatal control of photosynthesis
under wide range of environmental conditions prevalent in India. We studied the contribution of the enzyme ribulose-1,5 bisphosphate
carboxylase/oxygenase (Rubisco) in diurnal and seasonal photosynthesis changes in P. juliflora. The changes observed in photosynthesis under natural conditions could be effected by the growth temperatures, which ranged
from 10–30 °C in winter to 30–47 °C in summer. However, the Total Rubisco activity displayed a constant diurnal pattern and
showed a maximum at 1200 in all seasons namely spring, summer, monsoon and winter irrespective of the changes in temperature.
The Total Rubisco activity from two cohorts of leaves produced in spring and monsoon appeared to be down-regulated differentially
at low PPFD during the evening. The in vivo and in vitro measurements of carboxylation efficiency of Rubisco showed wide variation during the day and were correlated with the photosynthesis
rate. The light activation of Rubisco showed the acclimation to moderately high temperatures in different seasons except in
summer. The exceptionally high temperatures (>45 °C) in summer, though not affecting Total activity, severely inhibited the
light activation of Rubisco and also modulated the recovery process for the activation of Rubisco. Our studies suggest that
the modulation of Rubisco driven by Rubisco activase and not Rubisco per se was crucial for the diurnal regulation of photosynthesis.
NBRI Publication No.: 528 相似文献
20.
Michael J. Price Ian G. Campbell 《European journal of applied physiology and occupational physiology》1997,76(6):552-560
The thermoregulatory responses of ten paraplegic (PA; T3/4-L4) and nine able-bodied (AB) upper body trained athletes were
examined at rest and during prolonged arm-cranking exercise and passive recovery. Exercise was performed for 90 min at 80%
peak heart rate, and at 21.5 (1.7)°C and 47.0 (7.8)% relative humidity on a Monark cycle ergometer (Ergomedic 814E) adapted
for arm exercise. Mean peak oxygen uptake values for the PA and AB athlete groups were 2.12 (0.41) min−1 and 3.19 (0.38) l · min−1, respectively (P<0.05). At rest, there was no difference in aural temperature between groups [36.2 (0.4)°C for both groups]. However, upper
body skin temperatures for the PA athletes were approximately 1.0 °C warmer than for the AB athletes, whereas lower body skin
temperatures were cooler than those for the AB athletes (1.3 °C and 2.7 °C for the thigh and calf, respectively). Upper and
lower body skin temperatures for the AB athletes were similar. During exercise, blood lactate peaked after 15 min of exercise
for both groups [3.33 (1.26) mmol · l−1 and 4.30 (1.03) mmol · l−1 for the PA and AB athletes, respectively, P<0.05] and decreased throughout the remainder of the exercise period. Aural temperature increased by 0.7 (0.5)°C and 0.6 (0.4)°C
for the AB and PA athletes, respectively. Calf skin temperature for the PA athletes increased during exercise by 1.4 (2.8)°C
(P<0.05), whereas a decrease of 0.8 (2.0)°C (P<0.05) was observed for the AB athletes. During the first 20 min of recovery from exercise, the calf skin temperature of the
AB athletes decreased further [−2.6 (1.3)°C; P<0.05]. Weight losses and changes in plasma volume were similar for both groups [0.7 (0.5) kg and 0.7 (0.4) kg; 5.4 (4.9)%
and 9.7 (6.2)% for the PA and AB athletes, respectively]. In conclusion, the results of this study suggest that the PA athletes
exhibit different thermoregulatory responses at rest and during exercise and passive recovery to those of upper body trained
AB athletes. Despite this, during 90 min of arm-crank exercise in a cool environment, the PA athletes appeared to be at no
greater thermal risk than the AB athletes.
Accepted: 7 May 1997 相似文献