The Effects of Nitrate Supply and Grain Reserves on Fraction I Protein Level in the First Leaf of Barley

The timing and rate of nitrate application to barley seedlingsgrown under control and shade conditions can appreciably affectthe maximum amount of Fraction I protein attained in the firstleaf lamina. In unshaded seedlings early application resultsin a higher maximum amount of Fraction I protein per lamina,but not per unit lamina fresh weight. Late application of nitratehowever delays the age at which Fraction I protein reaches amaximum both in absolute terms and as a proportion of totalsoluble protein. For both control and shade-grown material earlyand higher rates of nitrate supply increase the maximum amountof soluble protein in the leaf but not the proportion representedby Fraction I protein. Lower rates of nitrate application havemuch less effect on first-leaf protein synthesis when applicationis given late. This is thought to be due to competition fromthe rapidly developing second leaf. Studies on the soluble protein content of shaded first-leaflaminae have shown that although grain size affects the maximumamount of Fraction I protein attained it does not alter theage at which this is attained; nor is the proportion of thetotal soluble protein accounted for by Fraction I protein affectedby grain size or grain nitrogen content. A model is proposed to explain the contribution made by grainreserves and exogenous carbon and nitrogen supply to the developmentof the soluble protein content of the first leaf.     

Photosynthetic acclimation of plants to growth irradiance: the relative importance of specific leaf area and nitrogen partitioning in maximizing carbon gain

Changes in specific leaf area (SLA, projected leaf area per unit leaf dry mass) and nitrogen partitioning between proteins within leaves occur during the acclimation of plants to their growth irradiance. In this paper, the relative importance of both of these changes in maximizing carbon gain is quantified. Photosynthesis, SLA and nitrogen partitioning within leaves was determined from 10 dicotyledonous C₃ species grown in photon irradiances of 200 and 1000 µmol m^?2 s^?1. Photosynthetic rate per unit leaf area measured under the growth irradiance was, on average, three times higher for high‐light‐grown plants than for those grown under low light, and two times higher when measured near light saturation. However, light‐saturated photosynthetic rate per unit leaf dry mass was unaltered by growth irradiance because low‐light plants had double the SLA. Nitrogen concentrations per unit leaf mass were constant between the two light treatments, but plants grown in low light partitioned a larger fraction of leaf nitrogen into light harvesting. Leaf absorptance was curvilinearly related to chlorophyll content and independent of SLA. Daily photosynthesis per unit leaf dry mass under low‐light conditions was much more responsive to changes in SLA than to nitrogen partitioning. Under high light, sensitivity to nitrogen partitioning increased, but changes in SLA were still more important.     

Induction of leaf senescence by low nitrogen nutrition in sunflower (Helianthus annuus) plants

Different parameters which vary during the leaf development in sunflower plants grown with nitrate (2 or 20 mM) for a 42‐day period have been determined. The plants grown with 20 mM nitrate (N+) showed greater leaf area and specific leaf mass than the plants grown with 2 mM nitrate (N?). The total chlorophyll content decreased with leaf senescence, like the photosynthetic rate. This decline of photosynthetic activity was greater in plants grown with low nitrogen level (N?), showing more pronounced senescence symptoms than with high nitrogen (N+). In both treatments, soluble sugars increased with aging, while starch content decreased. A significant increase of hexose to sucrose ratio was observed at the beginning of senescence, and this raise was higher in N? plants than in N+ plants. These results show that sugar senescence regulation is dependent on nitrogen, supporting the hypothesis that leaf senescence is regulated by the C/N balance. In N+ and N? plants, ammonium and free amino acid concentrations were high in young leaves and decreased progressively in the senescent leaves. In both treatments, asparagine, and in a lower extent glutamine, increased after senescence start. The drop in the (Glu+Asp)/(Gln+Asn) ratio associated with the leaf development level suggests a greater nitrogen mobilization. Besides, the decline in this ratio occurred earlier and more rapidly in N? plants than in N+ plants, suggesting that the N? remobilization rate correlates with leaf senescence severity. In both N+ and N? plants, an important oxidative stress was generated in vivo during sunflower leaf senescence, as revealed by lipid peroxidation and hydrogen peroxide accumulation. In senescent leaves, the increase in hydrogen peroxide levels occurred in parallel with a decline in the activity of antioxidant enzymes. In N+ plants, the activities of catalase and ascorbate peroxidase (APX) increased to reach their highest values at 28 days, and later decreased during senescence, whereas in N? plants these activities started to decrease earlier, APX after 16 days and catalase after 22 days, suggesting that senescence is accelerated in N‐leaves. It is probable that systemic signals, such as a deficit in amino acids or other metabolites associated with the nitrogen metabolism produced in plants grown with low nitrogen, lead to an early senescence and a higher oxidation state of the cells of these plant leaves.     

Physiological factors limiting growth and yield ofOryza sativa under unflooded conditions

Summary Rice grown under flooded conditions consistently produces better vegetative growth and higher grain yields than when grown in unflooded culture. Physiological and nutritional differences in rice grown under these two conditions were determined. Growth observations showed that plants under unflooded culture made an initial vigorous start, but soon showed poor tillering, depressed leaf growth, delayed flowering, low moisture content, foliar chlorosis, and 52.6 per cent lower yield than flooded plants.Chemical analysis emphasized the higher manganese content of plants grown under unflooded culture with no significant differences in other elements. Plants grown in nutrient cultures and under field conditions gave evidence that nitrate nitrogen nutrition, as exists for plants under unflooded conditions, favored manganese accumulation.Growth responses suggest differences in auxin metabolism. Since auxins could not be estimated directly, some factors affecting auxin degradation were investigated. It was found that plants grown under unflooded conditions had: 1) a low catalase activity, and: 2) a high peroxidase activity, which favor accelerated auxin degradation. It is proposed that high manganese levels in plants grown under unflooded conditions affects the indoleacetic acid oxidase mechanism resulting in retarded growth and depressed grain yields.     

Interaction of water supply and N in wheat

The purpose of this study was to investigate effects of N nutrition and water stress on stomatal behavior and CO₂ exchange rate in wheat (Triticum aestivum L. cv Olaf). Wheat plants were grown hydroponically with high (100 milligrams per liter) and low (10 milligrams per liter) N. When plants were 38 days old, a 24-day water stress cycle was begun. A gradual increase in nutrient solution osmotic pressure from 0.03 to 1.95 mega Pascals was achieved by incremental additions of PEG-6,000. Plants in both N treatments adjusted osmotically, although leaf water potential was consistently lower and relative water content greater for low N plants in the first half of the stress cycle. Leaf conductance of high N plants appeared greater than that of low N plants at high water potentials, but showed greater sensitivity to reductions in water potential as indicated by earlier stomatal closure during the stress cycle. The apparent greater stomatal sensitivity of high N plants was associated with a curvilinear relationship between leaf conductance and leaf water potential; low N plants exhibited more of a threshold response. Trends in [CO₂]_INT throughout the stress cycle indicated nonstomatal effects of water stress on CO₂ exchange rate were greater in high N plants. Although estimates of [CO₂]_INT were generally lower in high N plants, they were relatively insensitive to leaf water potential-induced changes in leaf conductance. In contrast, [CO₂]_INT of low N plants dropped concomitantly with leaf conductance at low leaf water potentials. Oxygen response of CO₂ exchange rate for both treatments was affected less by reductions in water potential than was CO₂ exchange rate at 2.5% O₂, suggesting that CO₂ assimilation capacity of the leaves was affected more by reductions in leaf water potential than were processes related to photorespiration.     

Effects of leaf age,nitrogen nutrition and photon flux density on the distribution of nitrogen among leaves of a vine (Ipomoea tricolor Cav.) grown horizontally to avoid mutual shading of leaves

Effects of leaf age, nitrogen nutrition and photon flux density (PFD) on the distribution of nitrogen among leaves were investigated in a vine, Ipomoea tricolor Cav., which had been grown horizontally so as to avoid mutual shading of leaves. The nitrogen content was highest in newly developed young leaves and decreased with age of leaves in plants grown at low nitrate concentrations and with all leaves exposed to full sunlight. Thus, a distinct gradient of leaf nitrogen content was formed along the gradient of leaf age. However, no gradient of leaf nitrogen content was formed in plants grown at a high nitrate concentration. Effects of PFD on the distribution of nitrogen were examined by shading leaves in a manner that simulated changes in the light gradient of an erect herbaceous canopy (i.e., where old leaves were placed under increasingly darker conditions with growth of the canopy). This canopy-type shading steepened the gradient of leaf nitrogen content in plants grown at a low nitrogen supply, and created a gradient in plants grown at high concentrations of nitrate. The steeper the gradient of PFD, the larger the gradient of leaf nitrogen that was formed. When the gradient of shading was inverted, that is, younger leaves were subjected to increasingly heavier shade, while keeping the oldest leaves exposed to full sunlight, an inverted gradient of leaf nitrogen content was formed at high nitrate concentrations. The gradient of leaf nitrogen content generated either by advance of leaf age at low nitrogen availability, or by canopy-type shading, was comparable to those reported for the canopies of erect herbaceous plants. It is concluded that both leaf age and PFD have potential to cause the non-uniform distribution of leaf nitrogen. It is also shown that the contribution of leaf age increases with the decrease in nitrogen nutrition level.     

Effect of nitrogen nutrition on the carbohydrate repression of photosynthesis in leaves of Phaseolus vulgaris L.

When carbohydrates accumulate in leaves, photosynthesis is repressed. Limited nitrogen nutrition is thought to enhance this repressing effect. However, the interaction between carbohydrate and nitrogen limitation in leaf photosynthesis has not been examined intensively. In this study, we grew Phaseolus vulgaris L. plants at three different nitrogen levels, and examined the effects of sucrose feeding to the roots on the nitrogen content, carbohydrate content and photosynthetic properties of the primary leaves. Nitrogen content and photosynthetic rate were lower and the carbohydrate content was greater in plants grown with limited nitrogen than in well-fertilized plants. Sucrose feeding to the plants increased carbohydrate content and decreased photosynthetic rate and nitrogen content. The increase in carbohydrate content and the decreases in nitrogen content and photosynthetic rate occurred at the same time, and the negative relationship between the carbohydrate content and photosynthetic rate did not differ among nitrogen nutrition levels. These results show that carbohydrate accumulation in the leaves leads to a decrease in photosynthetic rate. At low nitrogen nutrition levels, carbohydrates accumulated markedly, which accelerated this effect. It appears that the nitrogen nutrition level influences leaf photosynthesis through changing the carbohydrate level rather than through modifying sensitivity of the leaf to the carbohydrate level.     

Nitrogen reallocation and photosynthetic acclimation in response to partial shading in soybean plants

The first trifoliate of soybean was shaded when fully expanded, while the plant remained in high light; a situation representative for plants growing in a closed crop. Leaf mass and respiration rate per unit area declined sharply in the first few days upon shading and remained rather constant during the further 12 days of the shading treatment. Leaf nitrogen per unit area decreased gradually until the leaves were shed. Leaf senescence was enhanced by the shading treatment in contrast to control plants growing in low light. Shaded leaves on plants grown at low nutrient availability senesced earlier than shaded leaves on plants grown at high nutrient availability. The light saturated rate of photosynthesis decreased also gradually during the shading treatment, but somewhat faster than leaf N, whereas chlorophyll contents declined somewhat slower than leaf N.
Partitioning of N in the leaf over main photosynthetic functions was estimated from parameters derived from the response of photosynthesis to CO₂. It appeared that the N exported from the leaf was more at the expense of compounds that make up photosynthetic capacity than of those involved in photon absorption, resulting in a change in partitioning of N within the photosynthetic apparatus. Photosynthetic nitrogen use efficiency increased during the shading treatment, which was for the largest part due to the decrease in leaf N content, to some extent to the decrease in respiration rate and only for a small part to change in partitioning of N within the photosynthetic apparatus.     

烯效唑干拌种对小麦氮素积累和运转及籽粒蛋白质品质的影响

通过田间试验,研究了不同烯效唑干拌种剂量对3个不同筋力小麦品种植株氮素积累、运转和籽粒蛋白质品质的影响,结果表明,基因型、环境及烯效唑处理对小麦品质的影响效应依次减小,且均达到了极显著水平,但三者的互作效应较小。烯效唑处理后提高了不同生态点下不同小麦品种籽粒蛋白质含量和产量,处理后的面筋含量和沉淀值增加,面团形成时间和稳定时间延长;干拌种增加了开花期各营养器官中的氮素含量和单株氮素积累量,花后氮素总转移量、总转移率及其对籽粒氮的贡献率极显著提高,且处理后旗叶中可溶性蛋白质含量在花后15 d内均显著高于对照;对籽粒中氮含量而言,烯效唑处理后提高了灌浆初期籽粒中的非蛋白氮含量,花后5—20 d内均高于对照,灌浆期间籽粒蛋白氮含量均高于对照,因而处理后的粗蛋白质含量变化动态特点为谷底高、回升快。研究认为,烯效唑处理如同基因、环境一样独立影响小麦籽粒品质,而烯效唑处理后提高了开花初期旗叶中的可溶性蛋白质含量和花前营养器官中氮素含量及花后氮素转运量,可能是其提高籽粒非蛋白氮含量、促进籽粒蛋白质含量增加和蛋白质质量提高的重要原因之一,烯效唑干拌种对小麦籽粒蛋白质品质的改善具有广适性。     

The Effects of Shade Treatment and Light Intensity on Rihulose-1,5-Diphosphate Carboxylase Activity and Fraction I Protein Level in the First Leaf of Barley

It has been confirmed that shading leaves from day 5 onwardslowers the rate of CO₂ fixation when they are placed in saturatingirradiances. The reduction due to shade treatment is about 46per cent and a similar reduction in maximum chlorophyll contentof the leaf follows shading. Maximum amounts of total solubleprotein and of Fraction I protein are less in shaded leavesthan in control leaves and prolonged treatment leads to a declinein leaf protein content. The relative amounts of different proteinare also affected by treatment; in control leaves Fraction Iprotein accounts for about 45 per cent of the total but in shadedleaves the value is about 30 per cent. Increases and decreasesin leaf protein amount, with concomitant changes in the ratioof Fraction I to total protein can be brought about by removingshades and re-applying them. Such changes can be induced evenin fully expanded leaves in which net protein synthesis is notusually found. Maximal amounts of leaf protein are found in irradiances of60 W m^–2 or more, with lower values at lower light intensities.Where the first leaf is held in a stream of CO₂-free air a lowerlevel of protein is found. This, and the ratio of Fraction Ito total protein, are similar to values for shaded leaves, andsuggest the involvement of photosynthetic carbon fixation indetermining leaf protein amount. A 1:1 linear correlation between amount of Fraction I proteinand RuDP carboxylase activity is shown but the rate of CO₂ incorporationby leaf extracts is 2–3 times greater than that of theintact leaf. The significance of this and the effect of irradianceon leaf protein amount are discussed.     

Content of Oxalate in Actinidia Deliciosa Plants Grown in Nutrient Solutions with Different Nitrogen Forms

Kiwifruit plants (Actinidia deliciosa cv. Hayward) were grown in Hoagland nutrient solution with calcium nitrate, potassium nitrate, ammonium nitrate or ammonium chloride as the nitrogen source. Plants grown in the solution with nitrate nitrogen displayed a higher oxalate content, greater shoot length and leaf area, and higher content of ascorbic acid and NO₃ ^– ions in the leaves. Plants grown in the solution with ammonium nitrate, and particularly with ammonium chloride, showed low oxalate content, low content of ascorbic acid and NO₃ ^–, high content of Cl^– and Na⁺, low shoot length and leaf area. Oxalate formation appeared to be connected with the assimulation of nitrate, more precisely with nitrate reduction, while ammonium nitrogen assimilation did not induce the synthesis of oxalic acid.     

Mutual shading as a factor limiting the yield response of rice to application of nitrogen,phosphorus and potassium fertilizers

Summary The differences in fertilizer responses between rice plants grown under pot and field conditions were discussed.Under pot conditions, the rice plant responded more strongly to nitrogen applications at high phosphorus and high potassium levels than at low levels of these elements. This suggests that the balance of nitrogen, phosphorus, and potassium is an important factor in fertilizer application.Under field population conditions, however, mutual shading among plants limits grain yield. A big leaf area above a certain limit is associated with decreased grain yield. The response to nitrogen may be negative, and may not be changed even with the application of potassium and phosphorus.     

Effects of Elevated CO2 and High Temperature on Single Leaf and Canopy Photosynthesis of Rice

The increase of atmospheric CO2 concentration is indisputable. In such condition, photosynthetic response of leaf is relatively well studied, while the comparison of that between single leaf and whole canopy is less emphasized. The stimulation of elevated CO2 on canopy photosynthesis may be different from that on single leaf level. In this study, leaf and canopy photosynthesis of rice ( Oryza sativa L. ) were studied throughout the growing season. High CO2 and temperature had a synergetic stimulation on single leaf photosynthetic rate until grain filling. Photosynthesis of leaf was stimulated by high CO2, although the stimulation was decreased by higher temperature at grain filling stage. On the other hand, the simulation of elevated CO2 on canopy photosynthesis leveled off with time. Stimulation at canopy level disappeared by grain filling stage in beth temperature treatments. Green leaf area index was not significantly affected by CO2 at maturity, but greater in plants grown at higher temperature. Leaf nitrogen content decreased with the increase of CO2 concentration although it was not statistically significant at maturity. Canopy respiration rate increased at flowering stage indicating higher carbon loss. Shading effect caused by leaf development reached maximum at flowering stage. The CO2 stimulation on photosynthesis was greater in single leaf than in canopy. Since enhanced CO2 significantly increased biomass of rice stems and panicles, increase in canopy respiration caused diminishment of CO2 stimulation in canopy net photosynthesis, keaf nitrogen in the canopy level decreased with CO2 concentration and may eventually hasten CO2 stimulation on canopy photosynthesis. Early senescence of canopy leaves in high CO2 is also a possible cause.     

大气CO2浓度和温度升高对水稻叶片及群体光合作用的影响

大气ＣＯ２浓度升高对植物光合作用的影响研究多集中在单叶水平,在高ＣＯ２及高温下对植物单叶及群体光合进行比较的研究少有报道,而群体水平的研究则是预测生态系统反应所不可缺少的。采用田间开顶式培养室研究了大气ＣＯ２浓度和温度升高对水稻（ＯｒｙｚａｓａｔｉｖａＬ．）叶片及群体光合作用的影响。发现ＣＯ２浓度和温度对水稻叶片光合作用有协同促进作用,而对群体光合作用的促进则随时间的推移而减弱;单叶光合受到的促进作用大于群体光合;叶面积指数只在营养生长期受到促进,冠层叶片含氮量受ＣＯ２影响降低。群体呼吸（包括茎杆）增加及冠层叶片早衰可能是后期ＣＯ２对群体光合促进作用下降的原因。     

Uptake and incorporation of the products of proteolysis by the rumen bacteriumBacteroides ruminicola R8/4

The polypeptides of the proteolytic rumen bacteriumBacteroides ruminicola R8/4 grown in the presence of either leaf Fraction 1 protein, bovine serum albumin, or Bactocasitone as sole nitrogen source were separated by SDS-polyacrylamide gel electrophoresis. Over 40 polypeptides were resolved; the pattern for organisms grown on Fraction 1 protein was similar but not identical to that of the serum albumin and Bactocasitone-grown bacteria. All the bacterial polypeptides were distinguishable from the polypeptides of Fraction 1 protein (and serum albumin). The stained pattern was the same for organisms sampled at intervals during the growth of a batch culture. After incubation of the growing organisms with [¹⁴C]-Fraction 1 protein, all the bacterial polypeptides were labeled. Bacteria grown in the presence of nonlabeled Fraction 1 protein and a mixture of [^14C]-labeled amino acids incorporated label into all the polypeptides; the bacteria did not grow in the absence of intact protein, and then virtually no label was incorporated from the amino acid mixture.     

Hydraulic conductance as a factor limiting leaf expansion of phosphorus-deficient cotton plants

Suboptimal levels of phosphorus (P) strongly inhibited leaf expansion in young cotton (Gossypium hirsutum L.) plants during the daytime, but had little effect at night. The effect of P was primarily on cell expansion. Compared to plants grown on high P, plants grown on low P had lower leaf water potentials and transpiration rates, and greater diurnal fluctuations in leaf water potential. Hydraulic conductances of excised root systems and of intact transpiring plants were determined from curves relating water flow rate per unit root length to the pressure differential across the roots. Both techniques showed that low P significantly decreased root hydraulic conductance. The effects of P nutrition on hydraulic conductance preceded effects on leaf area. Differences in total root length, shoot dry weight, and root dry weight all occurred well after the onset of differences in leaf expansion. The data strongly indicate that low P limits leaf expansion by decreasing the hydraulic conductance of the root system.     

Nitrogen Assimilation and Leaf Development in Indeterminate Soybeans as Influenced by Post-Flowering Photoperiod

Guiamét, J. J., Balatti, P. A. and Montaldi, E. R. 1986.Nitrogen assimilation and leaf development in indeterminatesoybeans as influenced by post-flowering photoperiod.—J.exp. Bot. 37: 1611–1618. The effects of photoperiod on nitrogen fixation and leaf developmentin indeterminate soybeans were studied during early reproductivegrowth. Soybean plants cv. Williams were grown under short days(SD: 8 h-natural daylight (N.D.)+16 h-darkness) or long days(LD: 8 h-N.D. + 8 h-low intensity artificial light+ 8 h-darkness)from full bloom until mid pod filling. Long days greatly increased plant growth, both on the basisof leaf area or weight, mainly due to higher net assimilationrate. Average daily rates of N₂-fixation increased under LD;however, average N₂-fixation rates on a nodule weight or N basisdid not vary, suggesting that changes were not in nodule efficiencybut in nodule biomass. As compared to SD, LD reduced N contentin vegetative parts (pooled roots, stems and leaves), individualleaf blades and fruits. This seemed to be due to greater drymatter accumulation relative to N₂-fixation. The 2nd and 5th trifoliolate leaves showed larger specific leafweight (SLW) under LD. Soluble protein content on a dry weightbasis was higher in the 5th (younger) leaf than in the 2nd,but did not vary due to photoperiod. On the other hand, chlorophylland Fraction I protein content decreased in terms of dry weightunder LD. A larger proportion of leaf N was allocated to solubleproteins under LD, thus compensating for the lower N content.On the whole, growth enhancement by LD seemed unrelated to increasedavailability of N or to greater leaf soluble protein or FractionI content. Key words: Photoperiod, leaf development, soybean, nitrogen fixation     

Sagebrush carbon allocation patterns and grasshopper nutrition: the influence of CO2 enrichment and soil mineral limitation

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.     

生育前期遮光对水稻后期功能叶生长及稻米品质的影响

以2个不同直链淀粉含量的水稻品种为材料,研究了生育前期(插秧至幼穗分化期)遮光对水稻后期功能叶生长及稻米品质的影响。结果表明,前期遮光处理后,水稻剑叶面积明显增大,功能叶的碳、氮代谢水平提高;2个品种的籽粒直链淀粉积累过程受到的影响不同,而蛋白质积累受到的影响均一致(即百分含量下降幅度增大);糙米率有所降低,但未达到显著水平;精米率和垩白率极显著下降;整精米率和直链淀粉含量显著或极显著升高;粒长、粒宽和蛋白质含量无显著性变化,但蛋白质含量表现为下降趋势;2个品种间存在着差异。     

Does shoot water status limit leaf expansion of nitrogen-deprived barley?

The role of shoot water status in mediating the decline in leaf elongation rate of nitrogen (N)-deprived barley plants was assessed. Plants were grown at two levels of N supply, with or without the application of pneumatic pressure to the roots. Applying enough pressure (balancing pressure) to keep xylem sap continuously bleeding from the cut surface of a leaf allowed the plants to remain at full turgor throughout the experiments. Plants from which N was withheld required a greater balancing pressure during both day and night. This difference in balancing pressure was greater at high (2.0 kPa) than low (1.2 kPa) atmospheric vapour pressure deficit (VPD). Pressurizing the roots did not prevent the decline in leaf elongation rate induced by withholding N at either high or low VPD. Thus low shoot water status did not limit leaf growth of N-deprived plants.