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1.
Influence of ultraviolet-B (UV-B) radiation on photosynthetic and growth characteristics in field-grown cassava (Manihot esculentum Crantz) 总被引:2,自引:0,他引:2
The effects of ultraviolet-B (UV-B between 290 and 320 nm) on photosynthesis and growth characteristics were investigated in field grown cassava (Manihot esculentum Crantz). Plants were grown at ambient and ambient plus a 5.5kJ m?2 d?1 supplementation of UV-B radiation for 95 d. The supplemental UV-B fluence used in this experiment simulated a 15% depletion in stratospheric ozone at the equator (0°N). Carbon dioxide exchange, oxygen evolution, and the ratio of variable to maximum fluorescence (Fv/Fm) were determined for fully expanded leaves after 64–76 d of UV-B exposure. AH plants were harvested after 95 d of UV-B exposure, assayed for chlorophyll and UV-B absorbing compounds, and separated into leaves, petioles, stems and roots. Exposure to UV-B radiation had no effect on in situ rates of photosynthesis or dark respiration. No difference in the concentration of UV-B absorbing compounds was observed between treatments. A 2-d daytime diurnal comparison of Fv to Fm ratios indicated a significant decline in Fv/Fm ratios and a subsequent increase in photoinhibition under enhanced UV-B radiation if temperature or PPF exceeded 35°C or 1800μmol m?2 s?1, respectively. However, UV-B effects on fluorescence kinetics appeared to be temporal since maximal photosynthetic rates as determined by oxygen evolution at saturated CO2 and PPF remained unchanged. Although total biomass was unaltered with UV-B exposure, alterations in the growth characteristics of cassava grown with supplemental UV-B radiation are consistent with auxin destruction and reduced apical dominance. Changes in growth included an alteration of biomass partitioning with a significant increase in shoot/root ratio noted for plants receiving supplemental UV-B radiation. The increase in shoot/root ratio was due primarily to a significant decrease in root weight (–32%) with UV-B exposure. Because root production determines the harvest-able portion of cassava, UV-B radiation may still influence the yield of an important tropical agronomic species, even though photosynthesis and total dry biomass may not be directly affected. 相似文献
2.
Thomas Wallenda Christoph Schaeffer Werner Einig Astrid Wingler Rüdiger Hampp Bettina Seith Eckhard George Horst Marschner 《Plant and Soil》1996,184(2):291-298
During a seven-month period the effect of different nitrogen (N) availability in soil on growth and nutrient uptake was studied
in three-year-old Norway spruce (Picea abies [L.] Karst.) trees. The plants were grown in pots on N-poor forest soil supplied with various amounts and forms (inorganic
and organic) of N. Increasing supply of inorganic N (as NH4NO3) increased the formation of new shoots and shoot dry weight. The root/shoot dry weight ratio of new growth was drastically
decreased from 1.6 in plants without N supply to 0.5 in plants supplied with high levels of NH4NO3. This decrease in root/shoot dry weight ratio was associated with distinct changes in root morphology in favour of shorter
and thicker roots. The addition of keratin as organic N source did neither affect growth nor root morphology of the trees.
The amount of N taken up by plants was closely related to the supply of inorganic N, and trees supplied with highest levels
of NH4NO3 also had the highest N contents in the dry matter of needles and roots. In contrast, N contents in needles of trees grown
without additional N, or with keratin supply, were in the deficiency range. Supply of NH4NO3 decreased the contents of phosphate (P) and potassium (K) and therefore markedly increased N/P and N/K ratios in the needles.
On the other hand, the contents of calcium (Ca), magnesium (Mg), and manganese (Mn) in the needles were increased in the plants
supplied with inorganic N, suggesting high soil availability and promotion of uptake of these divalent cations by high nitrate
uptake. The observed effects on root/shoot dry weight ratio, root morphology, and mineral nutrient composition of the needles
indicated that high inorganic N supply may increase above-ground productivity but at the same time decrease the tolerance
of trees against soil-borne (e.g. deficiency of other mineral nutrients) stress factors.
Deceased 21 September 1996
Deceased 21 September 1996 相似文献
3.
Elcio Ferreira Santos Paula Pongrac Andr Rodrigues Reis Philip J. White Jos Lavres 《Physiologia plantarum》2019,166(4):996-1007
The fragmentary information on phosphorus (P) × zinc (Zn) interactions in plants warrants further study, particularly in plants known for their high P and Zn requirements, such as cotton (Gossypium hirsutum L.). The objective of this study was to investigate the effect of P × Zn interactions in a modern cultivar of cotton grown hydroponically. Biomass, mineral nutrition and photosynthetic parameters were monitored in plants receiving contrasting combinations of P and Zn supply. Root biomass, length and surface area were similar in plants with low P and/or low Zn supply to those in plants grown with high P and high Zn supply, reflecting an increased root/shoot biomass quotient when plants lack sufficient P or Zn for growth. Increasing P supply and reducing Zn supply increased shoot P concentrations, whilst shoot Zn concentrations were influenced largely by Zn supply. A balanced P × Zn supply (4 mM P × 4 μM Zn) enabled greatest biomass accumulation, while an imbalanced supply of these nutrients led to Zn deficiency, P toxicity or Zn toxicity. Net photosynthetic rate, stomatal conductance, transpiration rate and instantaneous carboxylation efficiency increased as P or Zn supply increased. Although increasing P supply reduced the P‐use efficiency in photosynthesis (PUEP) and increasing Zn supply reduced the Zn‐use efficiency in photosynthesis (ZnUEP), increasing Zn supply at a given P supply increased PUEP and increasing P supply at a given Zn supply increased ZnUEP. These results suggest that agricultural management strategies should seek for balanced mineral nutrition to optimize yields and resource‐use efficiencies. 相似文献
4.
Effects of atmospheric CO2 enrichment, water status and applied nitrogen on water- and nitrogen-use efficiencies of wheat 总被引:2,自引:1,他引:2
Atmospheric CO2 levels are expected to exceed 700 mol mol–1 by the end of the 21st century. The influence of increased CO2 concentration on crop plants is of major concern. This study investigated water- and nitrogen-use efficiency (WUE and NUE, respectively, were defined by the amount of biomass accumulated per unit water or N uptake) of spring wheat (Triticum aestivumL.) grown under two atmospheric CO2 concentrations (350 and 700 mol mol–1), two soil moisture treatments (well-watered and drought) and five nitrogen amendment treatments. Results showed that enriched CO2 concentration increased canopy WUE, and more N supply led to higher WUE under the increased CO2. Canopy WUE was significantly lower in well-watered treatments than in drought treatment, but increased with the increased N supply. Elevated CO2 reduced the apparent recovery fraction of applied N by the plant root system (Nr, defined as the ratio of the increased N uptake to N applied), but increased the NUE and agronomic N efficiency (NAE, defined as the ratio of the increased biomass to N applied). Water limitation and high N application reduced the Nr, NUE and NAE, indicating a poor N efficiency. In addition, there was a close relationship between the root mass ratio and NUE. Canopy WUE was negatively related to the root mass ratio and NUE. Our results indicated that CO2 enrichment enhanced WUE more at high N application, but increased NUE more when N application was less. 相似文献
5.
The effect of N supply on shoot and leaf lifespan was investigated in established stands of four herbaceous Carex species which differed in maximum dry matter production. These species were, in rank order of increasing maximum dry matter production (per unit ground area): Carex diandraC. rostrata. The observed patterns of shoot and leaf turnover were compared with data on leaf characteristics and nitrogen use efficiency indices of these species. There was no consistent difference in shoot production (number of shoots produced per unit ground area) between species with low production and those with high production: Carex diandra (low production) and C. lasiocarpa (high production) had high shoot production, while shoot production in c. rostrata (low production) and C. acutiformis (high production) was much lower. The rank order of the mean lifespan of shoots was: C. diandra. Thus, the lifespan of shoots increased with increasing maximum dry matter production of these Carex species. In all species, increased N supply led to a significant reduction in shoot lifespan. The reduction of shoot lifespans in response to enhanced N supply will result in increased nutrient turnover rates in these species. There was no consistent difference in the number of leaves produced per shoot between low-production and high-production species. C. diandra and C. lasiocarpa had relatively low leaf production, while C. rostrata and C. acutiformis had relatively high leaf production per shoot. Thus, this pattern is opposite to the pattern in shoot production. The rank order of the mean lifespan of leaves was: C. diandra. This implies that the high-production species had longer mean leaf lifespans than the low-production species. Mean leaf lifespan was not significantly affected by enhanced N supply, except in C. diandra, where leaf lifespan decreased in response to enhanced N supply. Shoot lifespans did not show any significant relation with the specific leaf area (SLA, leaf area per unit leaf mass) or the leaf area ratio (LAR, leaf area per unit plant mass) of the species under study. There was, however, a negative relation (r
2=0.71) with the nitrogen concentration in the leaves. Shoot lifespans were positively related (r
2=0.79) with whole-plant nitrogen use efficiency (NUE, dry matter production per unit N-loss) and with the mean residence time of nitrogen (MRT, the average time-span during which a unit of nitrogen is present in the plant) (r
2=0.78), but not with the nitrogen productivity (A, annual dry matter production per unit N in the plant). Leaf lifespan was positively related with the mean residence time of nitrogen in the plants (r
2–0.70). For all the other parameters, there were no significant relations with leaf lifespan. From these results we conclude that: (1) at the stand level, shoot and leaf lifespans are positively related with maximum dry matter production; and (2) shoot and leaf lifespan are important determinants of whole-plant nitrogen economy. 相似文献
6.
Influence of varied zinc supply on re-translocation of cadmium (109Cd) and rubidium (86Rb) applied on mature leaf of durum wheat seedlings 总被引:3,自引:0,他引:3
Cakmak I. Welch R.M. Erenoglu B. Römheld V. Norvell W.A. Kochian L.V. 《Plant and Soil》2000,219(1-2):279-284
Effect of varied zinc (Zn) supply (0, 0.1, 1, 5 M) on re-translocation of radio-labeled cadmium (109Cd) and rubidium (86Rb) from mature leaf to root and other parts of shoot was studied in 11-day-old durum wheat (Triticum durum cv. C-1252) plants grown in nutrient solution under controlled environmental conditions. Application of 109Cd and 86Rb was carried out by immersing the tips (3 cm) of mature leaf in radio-labeled solutions for 10 s at three different times over a 42 h period. Differences in Zn supply for 11 days did not affect plant growth nor did it cause visual leaf symptoms, such as necrosis and chlorosis, at either the lowest or the highest Zn supply. Only at the nil Zn supply (0 M), shoot and root dry weights tended to decrease and increase, respectively, causing a lower shoot/root dry weight ratio. Partitioning of more dry matter to roots rather than shoots, a typical phenomena for Zn-deficient plants in nutrient solution experiments, indicated existence of a mild Zn deficiency stress at the nil-Zn treatment. Irrespective of Zn supply, plants could, on average, retranslocate 3.8% and 38% of the total absorbed 109Cd and 86Rb from the treated leaf to roots and other parts of shoots within 42 h, respectively. At nil-Zn treatment, 2.8% of the total absorbed 109Cd was re-translocated from the treated leaf, particularly into roots. The highest re-translocation of 109Cd (6.5%) was found in plants supplied with 0.1 M Zn. Increases in Zn supply from 0.1 M reduced 109Cd re-translocation from 6.5% to 4.3% at 1 M Zn and 1.3% at 5 M Zn. With the exception of the nil-Zn treatment, the proportion of re-translocated 109Cd was greater in the remainder of the shoot than in the roots. Contrary to the 109Cd results, re-translocation of 86Rb was not (at 0, 0.1 and 1 M Zn), or only slightly (at 5 M), affected by changing Zn supply. The results indicate an inhibitory action of increased concentrations of Zn in shoot tissues on phloem-mediated Cd transport. This effect is discussed in relation to competitive inhibition of Cd loading into phloem sap by Zn. 相似文献
7.
Effects of supplied nitrogen form on growth and water uptake of French bean (Phaseolus vulgaris L.) plants 总被引:1,自引:0,他引:1
In order to investigate the effect of N form on dry matter (DM) formation and water uptake rate, French bean (Phaseolus vulgaris L. `Sotaxa') plants were grown with a split-root system. Three treatments were compared: sole nitrate (NO–
3) supply (NN), sole ammonium (NH+
4) supply (AA) and spatially separated supply of NO–
3 and NH+
4 (NA). The pH of the nutrient solutions was kept constant at 6.3 using a pH-stat system. 9 days after onset of the treatments, NN plants had higher root (36%) and shoot dry matter (11%) than AA plants. N form drastically influenced partitioning of assimilates: in the NA treatment, the root half exposed to NO–
3 revealed a 170% higher DM than the root half exposed to NH+
4. N form affected stable carbon-isotope discrimination () of leaf tissue. In leaves of plants which were supplied with NH+
4 (AA; NA) was significantly more negative (–29.4, –29.6) than in NN treatment (–28.2). We explain this effect by differences in stomatal conductance. We suppose that the significantly less negative of root tissue under NH+
4 supply is most probably related to higher PEP-case activity. The water uptake rate was higher in NN than in AA grown plants. This effect was found in both, short- and long-term experiments. In case of NA plants, the water uptake in the root part being exposed to NO–
3 was 104% higher than in those receiving NH+
4. At least in the case of the NA treatment we can exclude shoot growth effects as being responsible for differences in water uptake. We therefore assume that differences in root hydraulic conductivity are responsible for the observed effects. 相似文献
8.
Influence of UV-B radiation and Cd2+ on chlorophyll fluorescence, growth and nutrient content in Brassica napus 总被引:8,自引:0,他引:8
The possible interaction of two stresses, UV-B radiation and cadmium,
applied simultaneously, was investigated in Brassica
napus L. cv. Paroll with respect of chlorophyll fluorescence,
growth and uptake of selected elements. Plants were grown in nutrient
solution containing CdCl2, (0, 0.5, 2 or 5 M)
and irradiated with photosynthetically active radiation
(PAR, 400-700 nm, 800 mol m-2
s-1) with or without supplemental ultraviolet-B
radiation (UV-B, 280-320 nm, 15 kJ m-2
d-1, weighted irradiance). After 14 d of treatment,
the most pronounced effects were found at 2 and 5 M CdCl2 with and
without supplemental UV-B radiation. Exposure to cadmium significantly
increased the amount of Cd in both roots and shoots. In addition, increases
occurred in the concentrations of Fe, Zn, Cu, and P in roots, while K was
reduced. In shoots the S content rose significantly both in the presence
and absence of UV-B radiation, while significant increases in Mg, Ca, P,
Cu, and K occurred only in plants exposed to Cd and UV-B radiation.
Manganese decreased significantly under the combined exposure treatment.
The rise in S content may have been due to stimulated glutathione and
phytochelatin synthesis. Cadmium exposure significantly decreased root dry
weight, leaf area, total chlorophyll content, carotenoid content, and the
photochemical quantum yield of photosynthesis. As an estimation of energy
dissipation processes in photosynthesis, non-photochemical quenching
(qNPQ) was measured using a pulse amplitude modulated
fluorometer. The qNPQ increased with increasing Cd,
while the combination of cadmium and UV-B reduced the
qNPQ compared to that in plants exposed only to
cadmium or UV-B radiation. The chlorophyll a:b ratio
showed a reduction with UV-B at no or low Cd concentrations (0 M,
0.5 M CdCl2), but not at the higher Cd concentrations used (2
M, 5 M CdCl2). Thus in some instances there appeared to
be a UV-B and Cd interaction, while in other plants response could be
attributed to either treatment alone.Keywords:
Brassica napus, cadmium, ultraviolet-B
radiation.
相似文献
9.
Summary
Artemisia tridentata seedlings were grown under carbon dioxide concentrations of 350 and 650 l l–1 and two levels of soil nutrition. In the high nutrient treatment, increasing CO2 led to a doubling of shoot mass, whereas nutrient limitation completely constrained the response to elevated CO2. Root biomass was unaffected by any treatment. Plant root/shoot ratios declined under carbon dioxide enrichment but increased under low nutrient availability, thus the ratio was apparently controlled by changes in carbon allocation to shoot mass alone. Growth under CO2 enrichment increased the starch concentrations of leaves grown under both nutrient regimes, while increased CO2 and low nutrient availability acted in concert to reduce leaf nitrogen concentration and water content. Carbon dioxide enrichment and soil nutrient limitation both acted to increase the balance of leaf storage carbohydrate versus nitrogen (C/N). The two treatment effects were significantly interactive in that nutrient limitation slightly reduced the C/N balance among the high-CO2 plants. Leaf volatile terpene concentration increased only in the nutrient limited plants and did not follow the overall increase in leaf C/N ratio. Grasshopper consumption was significantly greater on host leaves grown under CO2 enrichment but was reduced on leaves grown under low nutrient availability. An overall negative relationship of consumption versus leaf volatile concentration suggests that terpenes may have been one of several important leaf characteristics limiting consumption of the low nutrient hosts. Digestibility of host leaves grown under the high CO2 treatment was significantly increased and was related to high leaf starch content. Grasshopper growth efficiency (ECI) was significantly reduced by the nutrient limitation treatment but co-varied with leaf water content. 相似文献
10.
In this study the influence of nitrogen nutrition on the patterns of carbon distribution was investigated with Urtica dioica. The nettles were grown in sand culture at 3 levels of NO?3, namely 3 (low), 15 (medium) and 22 (high) mM. These levels encompassed a range within which nitrogen did not affect total biomass production. The ratio of root: shoot biomass of the low nitrogen plants was, however, significantly higher than that of the nettles grown at medium and high N supply. Carbon allocation from one leaf of each pair of leaves was examined after a 14CO2-pulse and a subsequent 14C distribution period of one night. Only the youngest two leaf pairs did not export assimilates. Carbon (14C) export to the shoot apex and to the roots, as measured at the individual nodes responded to the nitrogen status: At medium and high nitrogen supply the 3rd, 4th and 5th leaf pairs exported to the shoot apex, while lower leaves exported to the root. At low nitrogen supply only the 3rd leaf exported towards the shoot apex. The results illustrate the plastic response of carbon distribution patterns to the nitrogen supply, even when net photosynthesis, carbon export from the source leaves and biomass production were not affected by the nitrogen supply to the plant. 相似文献
11.
R. T. Besford 《Plant and Soil》1979,51(3):341-353
Summary The effect of P nutrition on the growth of tomato plants in peat was examined. Initially, plants received an adequate supply of P and then received either nil, 0.78 or 2.34 kg superphosphate per m3 in combination with either 50 g N/ml (N1) or 300 g N/ml (N2) as ammonium nitrate in a liquid feed. Vegetative growth was restricted in the lower P treatmentsi.e. inhibited shoot growth, reduced duration of leaf expansion phase, thinner stems and reduced vegetative dry wt. Plants receiving N2 showed a greater restriction in growth compared with N1 plants when the P supply was limiting. P deficiency disrupted protein metabolism in the leaves, in that soluble leaf protein was reduced and trichloroacetic acid-soluble N accumulated. Flower development was accelerated by low P applications but the final numbers of flowers and the fruit-setting efficiency were reduced. Lowering the N supply reduced the fruit yield by 36 per cent while an intermediate P level reduced yields by about 15 per cent. Maximum fruit yields and good vegetative growth occurred when plants contained 0.4 per cent P or above in the mature leaves, and this value was achieved by adding the highest level (2.34 kg/m3) of superphosphate to the peat. 相似文献
12.
Cechin I Corniani N de Fátima Fumis T Cataneo AC 《Radiation and environmental biophysics》2008,47(3):405-413
The effects and interaction of drought and UV-B radiation were studied in sunflower plants (Helianthus annuus L. var. Catissol-01), growing in a greenhouse under natural photoperiod conditions. The plants received approximately 1.7 W m(-2) (controls) or 8.6 W m(-2) (+UV-B) of UV-B radiation for 7 h per day. The UV-B and water stress treatments started 18 days after sowing. After a period of 12 days of stress, half of the water-stressed plants (including both UV-B irradiated or non-irradiated) were rehydrated. Both drought and UV-B radiation treatments resulted in lower shoot dry matter per plant, but there was no significant interaction between the two treatments. Water stress and UV-B radiation reduced photosynthesis, stomatal conductance and transpiration. However, the amplitude of the effects of both stressors was dependent on the interactions. This resulted in alleviation of the negative effect of drought on photosynthesis and transpiration by UV-B radiation as the water stress intensified. Intercelluar CO(2) concentration was initially reduced in all treatments compared to control plants but it increased with time. Photosynthetic pigments were not affected by UV-B radiation. Water stress reduced photosynthetic pigments only under high UV-B radiation. The decrease was more accentuated for chlorophyll a than for chlorophyll b. As a measure for the maximum efficiency of photosystem II in darkness F (v)/F (m) was used, which was not affected by drought stress but initially reduced by UV-B radiation. Independent of water supply, UV-B radiation increased the activity of pirogalol peroxidase and did not increase the level of malondialdehyde. On the other hand, water stress did not alter the activity of pirogalol peroxidase and caused membrane damage as assessed by lipid peroxidation. The application of UV-B radiation together with drought seemed to have a protective effect by lowering the intensity of lipid peroxidation caused by water stress. The content of proline was not affected by UV-B radiation but was increased by water stress under both low and high UV-B radiation. After 24 h of rehydration, most of the parameters analyzed recovered to the same level as the unstressed plants. 相似文献
13.
Stage of development is an important determinant in the effect of nitrate on photoassimilate (13C) partitioning in chicory (Cichorium intybus) 总被引:1,自引:0,他引:1
Amziane R.; Delens E.; Noctor G.; Morot-Gaudry J-F.; Limami M.A. 《Journal of experimental botany》1997,48(1):25-33
The effect of nitrogen supply to chicory plants on carbon partitioningbetween shoot, root and tuberized root was studied at differentstages of vegetative growth, using long-term 13CO2 labelling-chaseexperiments. This approach was complemented by measurement ofstorage carbohydrates and activities of enzymes involved inroot sucrose metabolism (sucrose-sucrose fructosyl transferase(SST), sucrose synthase, invertase). In both young and matureplants, low resulted in a 3035% decrease in 13C assimilation. However, the partitioningof 13C between shoot and root was affected differently at differentstages of development. In young plants, in which carbohydrateswere being used for structural root and shoot growth, neither13C shoot/13C root ratio nor root activities of the above enzymeswere modified by supply. In contrast, in mature plants storing large amounts of carbohydratesas fructan in the tuberized root, low caused the ratio to decrease from 0.6 to 0.2, despiteunchanged net flux of 13C from shoot to root. The extractableactivity of SST was elevated in mature plants, compared to youngplants, at both low and high , consistent with its role in fructan synthesis. However, matureplants grown at low exhibited SST activity double that of plants grown at high . From these results, it is concluded that the observeddecrease in shoot/root dry weight ratio at low supply is caused by increased utilization of carbohydratesfor storage due to elevated root SST activity. Key words: Chicory, nitrate, 13C, shoot/root ratio, fructans, SST 相似文献
14.
W. J. ARP 《Plant, cell & environment》1991,14(8):869-875
Abstract. While photosynthesis of C3 plants is stimulated by an increase in the atmospheric CO2 concentration, photosynthetic capacity is often reduced after long-term exposure to elevated CO2 . This reduction appears to be brought about by end product inhibition, resulting from an imbalance in the supply and demand of carbohydrates. A review of the literature revealed that the reduction of photosynthetic capacity in elevated CO2 was most pronounced when the increased supply of carbohydrates was combined with small sink size. The volume of pots in which plants were grown affected the sink size by restricting root growth. While plants grown in small pots had a reduced photosynthetic capacity, plants grown in the field showed no reduction or an increase in this capacity. Pot volume also determined the effect of elevated CO2 on the root/shoot ratio: the root/shoot ratio increased when root growth was not restricted and decreased in plants grown in small pots. The data presented in this paper suggest that plants growing in the field will maintain a high photosynthetic capacity as the atmospheric CO2 level continues to rise. 相似文献
15.
A pot experiment with maize cv. Limac was conducted to investigate the influence of BAS 110.. W, a plant growth regulator (PGR), on root and shoot development and nutrient uptake. The PGR was applied via the soil with 0, 5, 10, 20, and 40 mg a.i. per pot. Shoot dry matter production was reduced to a higher degree than root length, resulting in a higher root-shoot ratio (RSR) of the treated plants. Shoots of treated plants contained higher concentrations of N, P, Ca, Mg, and unchanged K concentrations. The alterations in concentration could be explained by the changes in RSR induced by the plant growth retardant. The effect was strongest with P (+40%) which was limited by soil supply. N, Ca, and Mgconcentrations were positively influenced (+20%), there was no increase for Kvs RSR. 相似文献
16.
Adequate magnesium nutrition mitigates adverse effects of heat stress on maize and wheat 总被引:3,自引:0,他引:3
Aims
Heat stress is a growing concern in crop production because of global warming. In many cropping systems heat stress often occurs simultaneously with other environmental stress factors such as mineral nutrient deficiencies. This study aimed to investigate the role of adequate magnesium (Mg) nutrition in mitigating the detrimental effects of heat stress on wheat (Triticum aestivum) and maize (Zea mays).Methods
Wheat and maize plants were grown in solution culture with low or adequate Mg supply at 25/22 °C (light/dark). Half of the plants were, then, exposed to heat stress at 35/28 °C (light/dark). Development of leaf chlorosis and changes in root and shoot growth, chlorophyll and Mg concentrations as well as the activities of major antioxidative enzymes were quantified in the experimental plants. Additionally, maize plants were analyzed for the specific weights (e.g., dry or fresh weight per a given leaf surface area) and soluble carbohydrate concentrations of sink and source leaves.Results
Visual leaf symptoms of Mg deficiency were aggravated in wheat and maize when exposed to heat stress. In both species, root growth was more sensitive to Mg deficiency than shoot growth, and the shoot-to-root ratios peaked when heat stress was combined with Mg deficiency. Magnesium deficiency markedly reduced soluble carbohydrate concentrations in young leaf; but resulted in substantial increase in source leaves. Magnesium deficiency also increased activities of antioxidative enzymes, especially when combined with heat stress. The highest activities of superoxide dismutase (up to 80 % above the control), glutathione reductase (up to 250 % above the control) and ascorbate peroxidase (up to 300 % above the control) were measured when Mg-deficient plants were subjected to heat, indicating stimulated formation of reactive oxygen species (ROS) in Mg deficient leaves under heat stress.Conclusions
Magnesium deficiency increases susceptibility of wheat and maize plants to heat stress, probably by increasing oxidative cellular damage caused by ROS. Ensuring a sufficiently high Mg supply for crop plants through Mg fertilization is a critical factor for minimizing heat-related losses in crop production. 相似文献17.
Frédéric Henry Christophe Nguyen Eric Paterson Allan Sim Christophe Robin 《Plant and Soil》2005,269(1-2):181-191
The objective of this work was to determine if the impact of nitrogen (N) on the release of organic carbon (C) into the soil
by roots (rhizodeposition) correlated with the effect of this nutrient on some variables of plant growth. Lolium multiflorum Lam. was grown at two levels of N supply, either in sterile sand percolated with nutrient solution or in non-sterile soil.
The axenic sand systems allowed continuous quantification of rhizodeposition and accurate analysis of root morphology whilst
the soil microcosms allowed the study of 14C labelled C flows in physico-chemical and biological conditions relevant to natural soils. In the axenic sand cultures, enhanced
N supply strongly increased the plant biomass, the plant N content and the shoot to root ratio. N supply altered the root
morphology by increasing the root surface area and the density of apices, both being significantly positively correlated with
the rate of organic C release by plant roots before sampling. This observation is consistent with the production of mucilage
by root tips and with mechanisms of root exudation reported previously in the literature, i.e. the passive diffusion of roots
solutes along the root with increased rate behind the root apex. We proposed a model of root net exudation, based on the number
of root apices and on root soluble C that explained 60% of the variability in the rate of C release from roots at harvest.
The effects of N on plant growth were less marked in soil, probably related to the relatively high supply of N from non-fertiliser
soil-sources. N fertilization increased the shoot N concentration of the plants and the shoot to root ratio. Increased N supply
decreased the partitioning of 14C to roots. In parallel, N fertilisation increased the root soluble 14C and the 14C recovered in the soil per unit of root biomass, suggesting a stimulation of root exudation by N supply. However, due to
the high concentration of N in our unfertilised plants, this stimulation was assumed to be very weak because no significant
effect of N was observed on the microbial C and on the bacterial abundance in the rhizosphere. Considering the difficulties
in evaluating rhizodeposition in non sterile soil, it is suggested that the root soluble C, the root surface area and the
root apex density are additional relevant variables that should be useful to measure along with the variables that are commonly
determined when investigating how plant functioning impacts on the release of C by roots (i.e soil C, C of the microbial biomass,
rhizosphere respiration). 相似文献
18.
Effects of P deficiency on the uptake, flows and utilization of C, N and H2O within intact plants of Ricinus communis L. 总被引:1,自引:0,他引:1
Jeschke W. Dieter; Peuke Andreas; Kirkby Ernest A.; Pate John S.; Hartung Wolfram 《Journal of experimental botany》1996,47(11):1737-1754
The influence of P deficiency on the uptake, flow and utilizationof C, N and H20 by intact NO3-fed castor bean plants {Ricinuscommunis L.) was studied over a 9 d period in the middle oftheir vegetative growth. The modelling techniques incorporateddata on net increments or losses of C, N and H2O in plant parts,photosynthetic gains in and respiratory losses of C, molar C:Nratios of solutes in phloem and xylem sap and transpirationallosses of H20. Plant growth was inhibited within 3 d of withholdingP supply and dry matter production was less than one-third ofthe controls. Leaf growth was particularly depressed, whileroot growth was much less affected than that of the shoot. Shoot:rootratio of low-P plants was 1.5 compared with 2.6 under P supply.Over the 9 d study period total plant C and N increased by 560and 47 mmol, respectively, in the controls, but by only 113and 6.9 mmol in the low-P treatment. The particularly low incrementof N in P-deficient plants was due principally to decreasedN03- uptake. Flows of C and N during the study period were markedlydifferent between control and P-deficient plants. The partitioningprofile for C in P-deficient plants showed a dramatic inhibitionof net photosynthesis and attendant photoassimilate flow. Proportionaldownward to upward allocation of carbon increased with increasein sink size of the root relative to shoot. This was reflectedin greater relative allocation of C to root dry matter and rootrespiration than in P-sufficient plants, and suppressed cyclingof C from root to shoot via xylem. Nitrogen intake and xylemtransport to the shoot of P-deficient plants were only 15% ofthe control and, as in the case of C, downward allocation ofN predominated over upward phloem translocation. Apart fromthese severe changes, however, the basic patterns of N flowsincluding xylem-to-phloem and xylem-to-xylem transfer of N werenot changed, a feature highlighting the vital nature of thesetransfer processes even under deficiency conditions. The alterationsin flows and partitioning of C, N and H2O in response to low-Pconditions are discussed in relation to the corresponding effectsof moderate salt stress in Ricinus and the conclusion is reachedthat changes in nutrient flows under P deficiency were morehighly co-ordinated than when plants experience salt stress.Flow profiles under P deficiency which favour root growth andactivity are viewed as a means for increasing the potentialcapability of the plant to acquire P from the nutrient medium. Key words: Ricinus communis L., P deficiency, carbon, nitrogen, water, partitioning, xylem transport, phloem transport 相似文献
19.
Water and nitrogen (N) deficiency are two major constraints limiting the yield and quality of many oilseed crops worldwide.
This study was designed to assess the response of Camelina sativa (L.) Crantz to the availability of N and water resources on photosynthesis and yield parameters. All the measured variables,
which included plant height, root and shoot dry matter, root:shoot ratio, xylem pressure potential (XPP), yield components,
photosynthetic parameters, and instantaneous water-use efficiency (WUE) were remarkably influenced by water and nitrogen supply.
Net photosynthetic rate (P
N) and yield components were significantly decreased more by water deficit than by N deficiency. XPP, stomatal conductance
(g
s), and intercellular CO2 concentration (C
i) decreased substantially as the water deficit increased irrespective of the level of N application. WUE at the high N supply
[100 and 150 kg(N) ha−1] dropped in a large degree as the increased water deficit due to a larger decrease in P
N than transpiration rate (E). The results of this study suggest that the regulative capacity of N supply on photosynthetic and plant growth response
is significantly affected by soil water status and C. sativa is more sensitive to water deficit than N supply. 相似文献
20.