The effect of air temperature in successive periods of the growing season on sylleptic shoot formation in young apple trees

In two day-light phytotron rooms young apple trees were exposed to either 15 or 25°C in three successive periods of six weeks (Periods I, II and III) starting in the beginning of the growing season. A control group was kept outside throughout. Exposure to 15°C in either period had little effect on sylleptic growth; there was also hardly any difference with the outside treatment. At 25°C total sylleptic growth was greatly favoured especially when that temperature was applied in all three periods. However, 25°C given continuously did not affect sylleptic shoot number in Period II and III, but applied only in Period II or III greatly enhanced it. In a few cases there was a positive carry-over effect of 25°C given in Period I or II on sylleptic growth in the next period. No such carry-over effect was found for shoot number. Although temperature did influence growth of the parent shoot, that influence was much smaller than for sylleptic growth. The outgrowth of sylleptic shoots mainly occurred in periods when growth vigour of the parent shoot was highest. The distribution of sylleptic shoots along the parent shoot was greatly affected by the period in which the temperature of 25°C was applied suggesting that buds are only able to respond to outgrowth-inducing factors in a certain stage of development.     

Geographical Transition of Sylleptic/Proleptic Branching in Three Cinnamomum Species with Different Bud Types

Three native Japanese Cinnamomum(Lauraceae) species exhibiteither sylleptic and proleptic, or proleptic branching dependingon species-specific types of bud-structure (hypsophyllary andscaled-buds) and geographical distribution. Major branchingshifted from sylleptic at the axils of cataphylls and hypsophyllsin the southernmost C. doederleinii(latitudinal distributionrange 24–28° N) to both sylleptic at cataphyllary-and proleptic at hypsophyllary-axils in mid-latitudinal C. daphnoides(27–33°N), and to proleptic at the axils of foliage-leaves in the northernmostspecies C. japonicum(25–37° N). In all three Cinnamomumspecies, the sylleptic and proleptic branches expand aroundthe boundary between two successive yearly shoot-modules. Thepredominant, fertile axils having branches shifted from cataphylls(n year) and hypsophylls (n-1 year) in C. doederleinii and C.daphnoides, to foliage-leaves (n-1) in C. japonicum. The budsof proleptic branches at the axils of hypsophylls and foliage-leavesinevitably experience winter dormancy, hence the shoots areequipped with protective cataphylls instead of a hypopodium.Shoot length and leaf number gradually increased from the mostdistal cataphyllary sylleptic (n) shoots towards the most basalproleptic shoots at the axils of foliage-leaves (n-1). Prolepticshoots at the axils of foliage-leaves perform similarly to mainshoots in all three Cinnamomum species studied. The relativenumber of leaves borne on proleptic shoots gradually increasedfrom C. doederleinii, to C. daphnoides, and C. japonicum. Underthe seasonal, short growing periods of temperate latitudes,the increased shoot performance and bud protection of prolepticshoots are made possible through the earlier onset of bud formation(prolepsis) at the axils of the previous year's hypsophyllsand/or foliage-leaves in trees with rhythmic growth. Copyright2001 Annals of Botany Company Syllepsis, prolepsis, bud type, cataphyll, hypsophyll, shoot-growth cycle, evergreen broad-leaved tree, Cinnamomum doederleinii, Cinnamomum daphnoides, Cinnamomum japonicum     

Effect of Root and Shoot Meristem Temperature on Shoot to Root Dry Matter Partitioning and the Internal Concentrations of Nitrogen and Carbohydrates in Maize and Wheat

Maize (Zea mays L.) and spring wheat (Triticum aestivum L.)were grown in nutrient solution at uniformly high air temperature(20 °C), but different root zone temperatures (RZT 20, 16,12 °C). To manipulate the ratio of shoot activity to rootactivity, the plants were grown with their shoot base includingthe apical meristem either above (i.e. at 20 °C) or withinthe nutrient solution (i.e. at 20, 16 or 12 °C). In wheat, the ratio of shoot:root dry matter partitioning decreasedat low RZT, whereas the opposite was true for maize. In bothspecies, dry matter partitioning to the shoot was one-sidedlyincreased when the shoot base temperature, and thus shoot activity,were increased at low RZT. The concentrations of non-structuralcarbohydrates (NSC) in the shoots and roots were higher at lowin comparison to high RZT in both species, irrespective of theshoot base temperature. The concentrations of nitrogen (N) inthe shoot and root fresh matter also increased at low RZT withthe exception of maize grown at 12 °C RZT and 20 °Cshoot base temperature. The ratio of NSC:N was increased inboth species at low RZT. However this ratio was negatively correlatedwith the ratio of shoot:root dry matter partitioning in wheat,but positively correlated in maize. It is suggested that dry matter partitioning between shoot androots at low RZT is not causally related to the internal nitrogenor carbohydrate status of the plants. Furthermore, balancedactivity between shoot and roots is maintained by adaptationsin specific shoot and root activity, rather than by an alteredratio of biomass allocation between shoot and roots.Copyright1994, 1999 Academic Press Wheat, Triticum aestivum, maize, Zea mays, root temperature, shoot meristem temperature, biomass allocation, shoot:root ratio, carbohydrate status, nitrogen status, functional equilibrium     

Effects of Low Temperature on Growth and Nutrient Accumulation in Rye (Secale cereale) and Wheat (Triticum aestivum)

Rye (Secale cereale cv. Rheidol) and wheat (Triticum aestivumcv. Mardler) were grown at shoot/root temperatures of 20/20°C (warm grown, WG plants), 8/8 °C (cold grown, CG plants)and 20/8 °C (differential grown, DG plants). Plants fromcontrasting growth temperature regimes were standardized andcompared using a developmental timescale based on accumulatedthermal time (°C d) at the shoot meristem. Accumulationof dry matter, nitrogen and potassium were exponential overthe time period studied (150–550 °C d). In rye, therates of plant dry matter and f. wt accumulation were linearlyrelated to the temperature of the shoot meristem. However, inwheat, although the rates of plant dry matter and f. wt accumulationwere temperature dependent, the linear relationship with shootmeristem temperature was weaker than in rye. The shoot/rootratio of rye was stable irrespective of growth temperature treatment,but the shoot/root ratio of wheat varied with growth temperaturetreatment. The shoot/root ratio of DG wheat was 50% greaterthan WG wheat. In both cereals, nutrient concentrations anddry matter content tended to be greater in organs exposed directlyto low temperatures. The mean specific absorption rates of nutrientswere calculated for the whole period studied for each species/temperaturecombination and were positively correlated with both plant shoot/rootratio and relative growth rate. The data suggest that nutrientuptake rates were influenced primarily by plant demand, withno indication of specific nutrient limitations at low temperatures. Nutrient accumulation, relative growth rate (RGR), rye, Secale cereale cv. Rheidol, temperature, thermal time, Triticum aestivum cv. Mardler, wheat     

Correlative Inhibition in the Shoot of Agropyron repens ( L.) Beauv

Correlative inhibition was investigated in plants of Agropyronrepens at two temperatures. Reciprocal inhibition ocrurred betweenthe main shoot apex and the outgrowing axillary shoots, withthe balance of inhibition varying with temperature. Apical dominancewas stronger at 10 °C than at 20 °C , but even at 10°C release of apical dominance by decapitation had onlyminor effects on the timing of outgrowth, growth pattern andrate of dry weight aocumulation of the axillary shoots. Dominanceof the main shoot apex by the axillary shoots was stronger at20 °C than at 10 °C. Removal of axillary buds preventeddecline in size and activity of the main shoot apex ard resultedin increased rates of primordium initiation, leaf emergenceand dry weight accumulation in the main shoot. It is suggestedthat a system of reciprocal dominance provides a mechanism formaintaining the characteristic habit of the grass plant andlimits growth in height of vegetative shoots. Agropyron repens (L.) Beauv, couch grass, correlative inhibition, apical dominance, shoot, apex     

The Effect of Temperature on Growth and Development of Echinochloa Millets

Accumulation of dry weight and leaf plus stem area were measuredin Echinochloa utilis and E. frumentacea grown at temperatureregimes from 15/10°C to 33/28°C (day/night). Tilleringand height were recorded in addition to leaf number which wassubsequently used as a developmental index. In both species shoot dry weight increased with temperatureup to 33/28°C; the increase in relative growth rate (RGR)was negligible above 27/22°C. Below 27/22°C the RGRof E. frumentacea decreased sharply and at 15/10°C it madeno effective growth. At low temperatures the RGR of E. frumentaceawas lower than that of E. utilis due to slow leaf area expansion,and in particular smaller individual leaves. E. frumentaceatillered more than E. utilis. Plant development was retardedat low temperatures but was not as responsive to temperatureas dry weight and leaf area. The different responses to temperatureof the two species were described in equations suitable forinclusion in predictive growth models. Echinochloa spp., millet, growth, development, temperature, relative growth rate     

Growth, Development, and Yield of Spring Wheat in Artificial Climates

Spring wheat was grown to maturity in three growth rooms providing:(a) 18 h of light at 20° C and 6 h of darkness at 15°C (hot long days, HL); (b) 18 h of light at 15° C and 6h of darkness at 15° C (cold long days, CL); (c) 14 h lightat 20° C and 10 h of darkness at 15° C (hot short days,HS). Plants were moved between environments at spikelet initiationand anthesis, so dividing the growth period into three. Meanlengths in days of these periods in the different environmentswere: Period 1: HL 16, CL 18, HS 25; Period 2: HL 42, CL andHS 61; Period3: HL 53, CL 83, HS 63. The length of periods 2and 3 also depended on previous treatments. Grain dry weight was affected by environmental differences inall periods and effects in successive periods were additive.Compared with HL, CL or HS in period I before initiation increasedgrain yield by 6 per cent by increasing grain number per ear,HS in period 2 between initiation and anthesis decreased itby 24 per cent by decreasing the number of grains per spikeletand the proportion of spikelets that contained grain; CL inperiod 2 increased it by 21 per cent by increasing the numberof ears; CL in period 3 after anthesis increased it by 16 percent because leaves died later; HS in period 3 decreased itby 14 per cent because there was less radiation and hence lessphotosynthesis. Dry weight of shoot and root at maturity wasincreased by CL or HS in periods 1 or 2, and increased by CLand decreased by HS in period 3. The effects on final yieldof treatment during periods 1 and 2 were the consequence ofsimilar effects already produced at anthesis, and shoot androot dry weight changed little during period 3. The effects of environmental differences on grain dry weightcould not be explained by differences in leaf-area durationafter anthesis (D₃), except that CL in period 3 increased bothyield and D₃ but not proportionately, so that, as with HS inthe same period, grain: leaf ratio was decreased. Environmentaldifferences in periods 1 and 2 appeared to affect grain weightby altering the capacity of the ear to accumulate carbohydrates,determined by the number of grains per ear, rather than by alteringthe supply of carbohydrates, determined by D₃. There were some interactions between environments in differentperiods which were usually small compared with the main effects.     

Effect of Temperature on the Growth and Development of Tomato Fruits

Tomato fruits ripened 95, 65, 46 and 42 d after flower openingwhen plants were grown under controlled environmental conditionsat 14, 18, 22 and 26 °C, respectively. A similar responseto temperature was observed when the temperature of individualtrusses was modified while the plants were grown at 20 °C.These data were used to develop a thermal time model for fruitmaturation. However, when buds/fruits were heated at differentstages in their development, the thermal time model proved tobe a poor predictor of the time of ripening. Fruits were moresensitive to elevated temperature in their later stages of maturation.Temperature also affected the rates of fruit growth in volume;these could be adequately described using a Gompertz function.Low temperatures reduced absolute volume growth rates and delayedthe time at which the absolute growth rate became maximal. However,the response of fruit growth to temperature differed when onlythe temperature of the fruits was modified. There was a tendencytowards small parthenocarpic fruits at both high (26 °C)and low (14 °C) temperature regimes which, combined withlow flower numbers and poor fruit set at 26 °C, resultedin low fruit yields. Temperature also affected the shoot drymatter content and partitioning. Copyright 2001 Annals of BotanyCompany Tomato, Lycopersicon esculentum, fruit, growth, ripening, temperature, temperature stress, parthenocarpy     

Primary Growth and Re-growth of the Tropical Tallgrass Hybrid Pennisetum at Different Temperatures

Dry weight of plant fractions, leaf area, leaf number and tillernumber were recorded throughout primary growth and two subsequentre-growths of hybrid Pennisetum (Pennisetum americanum x P.purpureum) at five temperature regimes from 15/10 °C to33/28 °C (day/night) in summer and winter. Seedling mortality occurred at 15/10 °C, whereas at allhigher temperatures seedlings survived and plants re-grew aftercutting at a height of 10 cm. Shoot weights increased with temperatureup to 33/28 °C when compared at a common chronological agebut showed no differences at a common developmental age. Thetemperature response was associated with increased top/rootratio and rate of leaf appearance; mean individual leaf areaand NAR did not increase beyond 27/22 °C. Shoot weight incrementsin primary growth were the same in winter and summer when expressedper unit of radiation, although leaf area per unit weight wassensitive to changes in radiation associated with differencesin daylength. The rate of shoot weight accumulation in regrowthwas greater than in primary growth because of rapid tilleringfollowing defoliation and an enhanced rate of leaf appearanceper tiller. Pennisetum hybrid, tallgrass, growth, regrowth temperature response     

Effects of High Air and Soil Temperature Stress on Growth and Tuberization in Solanum tuberosum

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 (17–27C) at high air temperatures (30–40 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 (27–35 C) at cool (17–27 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     

Differential Inhibition of Shootvs.Root Growth at Low Temperature and its Relationship with Carbohydrate Accumulation in Different Wheat Cultivars

Shoot and root growth rate, carbohydrate accumulation (includingfructan), reducing sugar content and dry matter percentage weremeasured in six wheat cultivars, ranging from winter to springtypes, grown at either 5 or 25 °C. At 5 °C (comparedwith 25 °C), the relative growth rate (RGR) of shoots wassimilarly reduced in all cultivars, but the RGR of shoots wasmore affected in winter wheats. This difference resulted insmaller root:shoot ratios than in spring wheats, which alsodeveloped more first-order lateral roots. A direct relationshipbetween carbohydrate accumulation at low temperatures and reductionin root growth was established. These results suggest that differentialshootvs.root growth inhibition at low temperature may play akey role in carbohydrate accumulation at chilling temperatures.This differential response might lead to improvements in survivalat temperatures below 0 °C, regrowth during spring, andwater and nutrient absorption at low temperatures.Copyright1997 Annals of Botany Company Wheat; Triticum aestivum; low temperatures; root growth; root: shoot ratio; sugar accumulation     

Partition of photosynthates between shoot and root in spring wheat (Triticum aestivum L.) as a function of soil water potential and root temperature

Low soil water potential and low or high root temperatures are important stresses affecting carbon allocation in plants. This study examines the effects of these stresses on carbon allocation from the perspective of whole plant mass balance. Sixteen-day old spring wheat seedlings were placed in a growth room under precisely controlled root temperatures and soil water potentials. Five soil water potential treatments, from −0.03 MPa to −0.25 MPa, and six root temperature treatments, from 12 to 32°C were used. A mathematical model based on mass balance considerations was used, in combination with experimental measurements of rate of net photosynthesis, leaf area, and shoot/root dry masses to determine photosynthate allocation between shoot and root. Partitioning of photosynthates to roots was the lowest at 22–27°C root temperature regardless soil water potential, and increased at both lower and higher root temperatures. Partitioning of photosynthates to the roots increased with decreasing soil water potential. Under the most favourable conditions, i.e. at −0.03 MPa soil water potential and 27°C root temperature, the largest fraction, 57%, of photosynthates was allocated to the shoots. Under the most stressed conditions, i.e. at −0.25 MPa soil water potential and 32°C root temperature, the largest fraction, more than 80%, of photosynthates was allocated to roots.     

Internal Root Anatomy of Maize Seedlings (Zea mays L.) as Influenced by Temperature and Genotype

The objectives of this investigation were to determine: (a)the general effect of temperature on internal root anatomy;(b) whether genotypic differences in such root traits exist;and (c) the association between internal root traits and shootgrowth, lateral root branching and cold tolerance of maize (Zeamays L.). Seedlings of 20 central European hybrids were grownunder high or low temperature (25/22·5 °C or 15/12·5°C day/night temperatures) until the third leaf was fullyexpanded. Light microscopy of cross sections revealed a largerdiameter of primary roots at low temperature which was due toa larger stele diameter and a thickening of the cortex. Concurrently,an increase in total cross sectional area of metaxylem elementswas obtained. It is assumed that the modification of the internalroot structure by temperature has an effect on both axial andradial water flow capacity. For all anatomical traits studied,variability between genotypes was apparent under both growingconditions. Furthermore, different genotypic responses to temperaturewere observed. However, basic differences between cold-tolerantand cold-sensitive genotypes did not exist. While at high temperatureroot traits and shoot growth were significantly and positivelycorrelated, at low temperature the correlation coefficient wasinsignificant. Consequently, it was not possible to characterizethe performance of the shoot at low temperature based on anatomicaltraits of the root. Moderate, positive correlation coefficientswere obtained between internal root traits and lateral rootbranching. The potential use of root anatomical traits as indirectselection criteria is discussed. Chilling tolerance, genotypes, root anatomy, Zea mays L     

Effects of Photoperiod and Temperature on Shoot, Root and Rhizome Growth in ThreeLotus uliginosusSchkuhr Populations

The growth of three populations of greater lotus (Lotus uliginosusSchkuhrsyn.L. pedunculatusCav.) was compared at photoperiods of 10,12 and 14 h at a maximum day/minimum night temperature of 21/16°C and at maximum day/minimum night temperatures of 27/22,21/16, 18/13 and 15/10 °C at a photoperiod of 12 h. Shortdays (10 h) favoured root and rhizome development compared tolong days (14 h). A temperature regime of 15/10 °C restrictedrhizome development compared to the 18/13 and 21/16 °C regimes.Shoot growth was restricted at the highest temperature regime(27/22 °C). The cultivar Sharnae had fewer, but heavier,rhizomes than Grasslands Maku; this may indicate adaptationto the dry summers at its site of origin (Algarve, Portugal).The response of rhizome growth to temperature and photoperiodexplains part of the performance of greater lotus in the fieldat a wide range of latitudes. Grazing management to encouragethe persistence ofL. uliginosusin pasture in temperate environmentsmay include the exclusion of grazing livestock in autumn. Inthe sub-tropics, monitoring of rhizome production in the fieldwould be required before deciding the appropriate time intervalbetween grazing.Copyright 1998 Annals of Botany Company Lotus uliginosus(Schkuhr); greater lotus; temperature; daylength; shoots; roots; rhizomes.     

Pattern of Shoot Growth in Zizyphus mauritiana and Z. oenoplia

Shoot polymorphism and patterns of sylleptic branching and shoottip abscission in two Zizyphus species are reported. Z. mauritiana(ber) produced three types of proleptic shoots: vigorous, normaland spur-type, by reiteration or following pruning;Z. oenopliahad only one type of shoot. Both species revealed up to thirdorder sylleptic branching on the vigorous proleptic shoots witha characteristic pattern and rhythm. Bud dormancy breaking chemicalsgiven as pre-pruning foliar sprays in ber, did not alter thepattern of sylleptic branching. Zizyphus oenoplia produced morefirst and second order sylleptic branches compared to Z. mauritiana.All main axes and 97% of first order sylleptic branches ofZ.mauritiana abscised their apical buds during summer, but inZ. oenoplia all main axes and 54% of first order sylleptic branchesremained active. Shoot tip abscission was almost complete onthe higher order sylleptic branches of both species. Activefirst order branches in Z. oenoplia were confined to the tophalf of the shoot. Both species had a few dormant apical budsduring the summer on their sylleptic branches, emerging mostlyfrom the middle portion of the shoot. Some of the most vigorousfirst order branches of Z. oenoplia, which had dormant apicalbuds during summer, showed a change in the frequency of syllepticbranching when they resumed growth following monsoon showers.These characteristic growth and branching patterns may haveadaptive value for canopy development under arid and semi-aridconditions. Copyright 1999 Annals of Botany Company Ber, branching pattern, shoot polymorphism, shoot tip abscission, sylleptic branching, Zizyphus mauritiana, Zizyphus oenoplia.     

Effects of Low Temperature on the Development and Morphology of Rye (Secale cereale) and Wheat (Triticum aestivum)

Seedlings of Secale cereale cv. Rheidol and Triticum aestivumcv. Mardler were grown at shoot/root temperatures of 20/20 °C,20/8 °C and 8/8 °C. During vegetative growth both cerealsproduced leaves, tillers and roots in a defined pattern, ata species-specific rate which was linearly related to the temperatureof the shoot meristem. Thus, plant development could be standardizedon a temperature x time (°C d) basis despite contrastinggrowth-temperature treatments. When compared at a similar developmentalstage, the cooling of whole plants or of plant roots resultedin an increase in the d. wt: f. wt ratio of both shoot and roottissues, a decrease in the length of both the longest shootand root, and the development of broader and thicker leaves.Although the effects of temperature on developmental characteristicscould be accurately predicted by an empirical relationship,the effects on morphological characteristics could not. Development, phyllochron, rye, Secale cereale cv. Rheidol, temperature, thermal time, Triticum aestivum cv. Mardler, wheat     

Effect of Temperature on Interception and Conversion of Solar Radiation by Stands of Groundnut

Stands of groundnut were grown in controlled environment glasshousesat air temperatures of 19, 22, 25, 28, and 31°C. Leaf areaindex (L) increased with rise of temperature, and after 85 dwas about 10-fold larger at 31°C than 19°C. Over mostof the range of temperature, both L and fractional interceptionof solar radiation (f) were functions of thermal time accumulatedfrom sowing (above a base of 10°C). In this respect, theywere tightly coupled to developmental rate at the main apex.In one experiment, only 38% of seeds emerged at 22°C and21% at 19°C, compared with more than 70% at 25°C and31°C, but the low population density was compensated byfaster leaf expansion by each plant (at 22°C only) and agreater fraction of solar radiation intercepted by unit leafarea. The amount of solar radiation intercepted by stands increasedwith rise in temperature, but the greatest differences betweentreatments occurred before the canopies achieved complete groundcover (i.e.f>0.9) and the relative effect of a rise in temperaturediminished the longer the duration of growth. The dry matterproduced for unit solar radiation intercepted was not stronglyaffected by temperature between 22°C and 31°C, wherethe mean was 2.1 g MJ^–1; the value at 19°C was uncertainsince the stands were sparse throughout the experiment. After85 d, the stand at 31°C had produced eight times the drymatter of that at 19°C—a difference caused mainlyby the effect of temperature on the rates of development andexpansion. Key words: Dry matter production, groundnut, radiation interception, temperature, thermal time, roses     

Shoot Elongation in Scots Pine: Diurnal Variations and Response to Temperature

Kanninen, M. 1985. Shoot elongation in Scots pine: Diurnal variationsand response to temperature.—J. exp. Bot. 36: 1760–1770. Time series analysis is used to study the diurnal variationsin the rate of shoot elongation of Scots pine (Pinus sylvestrisL.) seedlings, and its response to temperature. The shoot elongation of three 5-year-old Scots pine seedlingswas measured at 2 h intervals over a 12 d period in June 1979.Ambient temperature, measured with a thermocouple, was continuouslyrecorded during the same period. The measurements were carriedout in the field. Time series analysis of the data was carried out by estimatedauto-correlation and partial auto-correlation functions. A multiplicative‘seasonal’ model was applied to both the input andoutput series to ‘prewhiten’ the data set. Serialcross-correlation analysis of the prewhitened series was usedto identify the structure of the transfer function model betweentemperature and growth rate. There was a phase shift between the air temperature and shootextension. The cross-correlation function peaked at 2 h lagvalue. The influence of temperature on the growth rate was adequatelydescribed by a first-order transfer function model. The characteristicfeature of the model was a time constant of 3.3 h and a basetemperature of 6.3 °C for the response of shoot elongationto temperature. Key words: Scots pine, Pinus sylvestris L., shoot elongation, temperature response, time-series analysis     

Environmental Factors Controlling Flower Opening and Closing in aPortulacaHybrid

To examine flower opening and closing of aPortulacahybrid, flowerbuds were placed in darkness for 12 h (2030–0830 h) at20 °C and then exposed to various light-temperature conditions.Flower buds exposed to light at 25, 30 or 35 °C opened within1 h, and wilted 10–14 h later. Flower buds exposed tolight at 20 °C started to open after 4 h but opened slowlyand not completely. Flower buds subjected to 25, 30 or 35 °Cin darkness also opened rapidly, but did not reach full opening.Flowers opened at 30 °C in light, and partially closed andopened repeatedly in response to cycles of a 2-h exposure to20 °C and a 2-h exposure to 30 °C at any time between1000 to 1600 h. Similar phenomena were observed when the flowersopened at 30 °C in light and then were subjected to darknessand light alternately at 30 °C, although the effect of lightwas less obvious than that of alternating temperature. Floweropening and closing were not affected by relative humidity.These results indicate that a rise in temperature is requiredfor rapid flower opening in the buds kept at 20 °C, andthat light intensifies the effect of high temperature. Exposureto light without a temperature change delayed and slowed floweropening which was never complete. The involvement of an endogenousrhythm in flower opening byPortulacais indicated. Portulacahybrid, flower opening, flower closing, temperature shift, endogenous rhythm.     

Effect of Temperature on Growth of Crotalaria juncea L. and Crotalaria sericea Retz.

Growth performances of Crotalaria juncea L. and C. sericea Retz.have been compared at two controlled temperatures, 16–20°C, and 28–32 °C, with respect to increase ind. wt and leaf area, relative growth rate, leaf area ratio,specific leaf area, leaf weight ratio, net assimilation rate,the ratio of mean relative growth rate to mean relative rateof leaf area increase () and shoot/root ratios. Both the speciesgrew better at the higher temperature; however the relativegrowth rate was more affected by temperature in C. sericea thanin C. juncea. Further, it was observed to be more dependenton net assimilation rate than on the leaf area ratio. Crotalaria juncea L., Crotalaria sericea Retz., relative growth rate, leaf area ratio, specific leaf area, leaf weight ratio, leaf area increase, net assimilation rate, shoot/root ratio