Seasonal Patterns of Photosynthetic Traits in Early Maturing Maize

A biochemical approach to maize breeding must be based on an exact knowledge about changes of relevant traits with ontogenetic stage. In 1983 seasonal patterns of net assimilation rate (NAR), chlorophyll and carotenoids contents, and of activities of RuBP carboxylase, PEP carboxylase and NADP malate dehydrogenase were recorded for two early maturing maize cultivars. For all traits the general trends were similar for both cultivars throughout the growing season but short term fluctuations were less synchronized after anthesis. About 75% of the maximum green leaf area was expanded within 20 days around middle of July. Specific seasonal patterns were observed for all traits. Before anthesis values were maximum for NAR in late June and in early July, for enzyme activities at the end of June and for pigment contents at the beginning of July. First decreases occurred for all traits before anthesis, further decreases were observed for PEP carboxylase in August and for chlorophyll content in September. Marked temporary declines coincided for NAR and pigment contents with a cold spell end of June and for these traits and RuBP carboxylase activity with anthesis. Evidence was scarce that any of the photosynthetic traits reflected the photosynthetic efficience of the two cultivars for a long stretch of time.     

不同灌溉条件下冠菌素对大豆光合特性与产量的调控效应

干旱是限制大豆丰产稳产的重要因素之一,利用生物调节剂提高大豆耐旱性是生产中一种新型的生物节水管理模式。本研究在常规灌溉与无灌溉条件下,采用生物调节剂冠菌素(COR)于大豆初花期进行叶面喷施处理,研究COR对植株农艺性状、叶片水势和光合特征、产量及其构成因素的调控效应。试验结果表明:在正常灌溉条件下, COR处理对大豆叶片水势、叶绿素含量、光合速率、叶绿素荧光参数、RuBP羧化酶和SPS活性等影响较小,与对照相比其产量和生物量差异不显著。但在生长季无灌溉的雨养条件下,COR处理会显著提高大豆开花后叶片水势、叶绿素含量、光合速率和叶绿素荧光参数,增加叶片RuBP羧化酶和SPS活性,改善大豆产量构成因素,最终导致籽粒产量增加。总之,在雨养条件下, COR对大豆光合特征和产量形成具有积极的调控效应。     

Responses of carbon metabolism and antioxidant system of summer maize to waterlogging at different stages

A field experiment was performed to explore responses of carbon metabolism, antioxidant system and endogenous hormone content of summer maize hybrids DengHai605 (DH605) and ZhengDan958 (ZD958) to waterlogging at the third leaf stage (V3), the sixth leaf stage (V6) and the 10th day after the tasselling stage (10VT). Results showed that waterlogging significantly decreased the contents of zeatin riboside (ZR), indole‐3‐acetic acid (IAA) and gibberellic acid (GA), compared to those of CK. However, leaf abscisic acid (ABA) content was significantly increased by waterlogging at different stages, with the most significant increase was found in the treatment of waterlogging at V3 (V3‐W), with an increase of 30% and 29% for DH605 and ZD958, respectively. Waterlogging significantly decreased antioxidative enzyme activities, accelerating leaf senescence, resulted in the disorder of leaf gas exchange parameters and chlorophyll fluorescence parameters. In addition, waterlogging decreased key enzyme activities of carbon metabolism (ribulose bisphosphate carboxylase and phosphoenolpyruvate carboxylase), with the most significant reduction in V3‐W, with a decrease of 46% and 49% for DH605, and 53% and 55% for ZD958, respectively. Visibly, waterlogging disturbed carbon metabolism, affected plant endogenous hormone content, accelerated leaf senescence and eventually resulted in a significant reduction in photosynthetic characteristic and grain yield. V3 was most susceptible to waterlogging, followed by V6 and 10VT.     

Productivity of Maize (Zea mays L.) in Relation to Morphological and Physiological Characteristics under Varying Amounts of Nitrogen Supply

In a field trial located in a northern region of Germany, characterized by a Podzol soil and increasing N fertilization resulted in an enhanced N uptake of the maize (Zea mays L.) variety “Felix” with increasing N fertilization ranging from 0 kg N ha^-1 (N1) to 60 kg N ha^-1 (N2) and to 160 kg N ha^-1 (N3). The growth conditions reached only nearly optimal temperature for biomass allocation in a short period of July and August 1990. The plant productivity was stimulated due to higher N uptake and N utilization to values of nearly 1600 g ha^-1. The N efficiency decreased with increasing N fertilization. A greenhouse experiment was conducted to study the effects of varied nitrogen nutrition on the development of maize plants under standardized growth conditions, comparable to the sub optimal growth conditions of the field experiment. Physiological and anatomical parameters were measured. Within a range of 0.2—1.0 mg N cm^-2 of leaf nitrogen, the chlorophyll concentration and the CO₂ exchange rate showed a linear relationship with the reduced N in the leaf. Above 1.0 mg N cm^-2 no further increases in chlorophyll levels or photosynthesis were observed. Nitrate reductase activity was stimulated throughout the N range supplied. The activities of photosynthetic enzymes (PEP carboxylase, Nadp malic enzyme, RubP carboxylase) was increased from the low (0.19 g N kg^-1 soil) to the middle N level (0.37 g N kg^-1 soil). Under conditions of a high N supply (0.75 g N kg^-1 soil) the activity decreased, except Nadp malic enzyme. This effect was accompanied by alterations of the internal structure of the leaf. Leaf thickness and size of the mesophyll parenchyma were less at the medium nitrate supply. Other anatomical parameters were influenced in proportion to leaf nitrogen status. Stomatal index was not affected by N supply, but lengths and widths of epidermal and stomatal cells as well as the distance between stomata and vascular bundles were increased by high N supply. It is proposed that above an optimal range of leaf nitrogen, maize plants cannot use the potential advantage of the C₄ mechanism and the N utilization shows maximum efficiency in the intermediate N level under the sub optimal growth conditions used in the greenhouse experiment.     

钾对小麦旗叶蛋白水解酶活性和籽粒品质的影响

利用强筋冬小麦品种烟农15研究了钾素对小麦旗叶蛋白质含量和籽粒品质及有关酶活性的影响. 结果表明, 钾素有利于提高灌浆前期和中期小麦旗叶中可溶性蛋白质和游离氨基酸的含量, 增强内肽酶和羧肽酶的活性, 促进籽粒中游离氨基酸转化为蛋白质, 提高籽粒中清蛋白、球蛋白、醇溶蛋白和谷蛋白的含量, 改善籽粒营养品质和加工品质     

杂交稻及其三系生育过程中RuBP羧化酶及有关光合酶的变化

研究了杂交稻汕优６３及其三系生育过程中叶片ＲｕＢＰ羧化酶／加氧酶及有关光合酶活性的变化,结果表明,供试材料ＲｕＢＰ羧化酶／加氧酶等参数的变化无本质的差异。杂交稻不同叶位叶片的ＲｕＢＰ羧化酶活性低于其母不育系,但与父本较接近。从ＲｕＢＰ羧化酶／加氧酶这一光合特征值来分析,杂交稻叶片并不存在光合优势。随着叶龄增加,杂交稻及其三系叶片的ＲｕＢＰ羧化酶／加氧酶、乙醇酸氧化酶、过氧化氢酶活性下降,而酸性磷酸     

Nitrogen Rates and Water Stress Effects on Production, Lipid Peroxidation and Antioxidative Enzyme Activities in Two Maize (Zea mays L.) Genotypes

Effects of nitrogen rates and water stress (WS) on production, lipid peroxidation and antioxidative enzyme activities in two maize (Zea mays L.) genotypes were assessed at different stages under two levels of water supply conditions. WS caused a significant decline in dry matter, grain yield and activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) whereas a marked rise in malondialdehyde (MDA) concentration was observed in leaves for the two genotypes. However, the responses of the two varieties to WS were different: significantly higher dry matter, grain yield and antioxidative enzyme activities and lower MDA content were observed for Shaandan 9 than Shaandan 911, therefore the former could be treated as a drought tolerance variety comparatively. A better correlation was obtained amongst dry matter, grain yield and physiological traits. The addition of nitrogen increased dry matter and grain yield as well as activities of SOD, POD and CAT to different levels and significantly decreased MDA content under WS. These effects were higher for Shaandan 911 than for Shaandan 9. Furthermore, a significant effect was found for Shaandan 911 between N rates for all traits unlike Shaandan 9. Hence, we suggest that nitrogen should be applied to a water‐sensitive variety to bring out its potential fully under drought.     

水稻光合关键酶类在光合日变化中的作用

研究了2个水稻品种的剑叶净光合速率(Pn)、Rubisco初始活力和Rubisco活化酶活力、Rubisco活化酶含量和ATP含量的日变化，以明确在体内Rubisco活化酶是否对光合作用和Rubisco活力的日变化起调节作用。结果表明，2个品种剑叶的Pn、Rubisco初始活力和Rubisco活化酶活力在一天内变化较大，三者的日变化模式基本一致，即具有两个峰     

Oil biosynthesis and its related variables in developing seeds of mustard (<Emphasis Type="Italic">Brassica juncea</Emphasis> L.) as influenced by sulphur fertilization

The aim of this research was to study the effect of sulphur (S) fertilization on oil biosynthesis and its related variables at various stages of seed development, and to find possible explanations for increased oil content in the seeds of mustard (Brassica juncea L. Czern and Coss) due to S fertilization. Acetyl-CoA carboxylase activity and contents of oil, acetyl-CoA, soluble protein, total RNA, total sugar and sulphur were determined in the developing seeds of mustard grown in the field with sulphur (+S) and without sulphur (-S). The period between 10 to 30 days after flowering was observed as the active period of oil accumulation in the developing seeds of mustard. The accumulation of the oil was preceded by a marked rise in acetyl-CoA carboxylase activity and acetyl-CoA concentration, which declined rapidly when oil accumulation reached a plateau. Total sugar content decreased, while protein content increased during the active period of oil accumulation in the developing seeds (i.e. between 10–30 days after flowering). Sulphur fertilization significantly (P < 0.05) enhanced the oil accumulation in the developing seeds at all the growth stages. The increase in the oil content was 5–63% with S fertilization over the control treatment. Acetyl-CoA carboxylase activity and contents of acetyl-CoA, soluble protein, total RNA and sugar were significantly (P < 0.05) higher in the developing seeds of +S-treated plants compared to — S-treated plants. It is suggested that the increase in the oil content with sulphur fertilization may be associated with the increases in acetyl-CoA carboxylase activity through the enhancement of acetyl-CoA concentration. Further, the increased sugar content due to S fertilization provided enough carbon source and energy for oil biosynthesis.     

油菜素内酯对春玉米灌浆期叶片光合功能与产量的调控效应

以玉米品种"郑单958"为材料,在大田条件下,采用植物生长调节物质油菜素内酯(brassinolide,BR)对苞叶和穗位叶喷施处理,研究了BR对玉米穗位叶功能、籽粒灌浆及产量的调控作用。结果表明,灌浆期随生育进程,玉米穗位叶叶绿素含量、光合速率、磷酸烯醇式丙酮酸羧化酶(PEPCase)、1,5-二磷酸核酮糖羧化酶(Ru BPCase)以及蔗糖磷酸合酶和蔗糖合酶的活性均显著下降。同时,籽粒蔗糖含量显著降低,但淀粉含量和粒重均显著增加。与对照相比,BR处理显著增加玉米穗位叶叶绿素含量,提高光合速率,增强PEPCase、Ru BPCase、蔗糖磷酸合酶和蔗糖合酶的活性。BR处理显著增加籽粒蔗糖和淀粉积累,提高玉米籽粒干物质积累。在产量构成上,BR显著缩短秃尖长度,增加穗粒数和千粒重,显著提高产量。本研究说明,灌浆期喷施BR可提高玉米叶源的活性,延长叶片光合功能持续期,促进籽粒灌浆和物质积累,从而实现增产。     

土壤水分对豫麦34花后GS同工酶及籽粒产量与蛋白质含量的影响

采用盆栽方法,连续两年研究了豫麦34在田间最大持水量40%(40%FC)、60%(60%FC)和80%(80%FC)条件下花后旗叶与籽粒中谷氨酰胺合成酶(GS)及其同工酶活性和可溶性蛋白含量及籽粒产量等的变化特征。结果表明,旗叶中GS活性较同期籽粒中GS活性高10倍以上,并均在波动中下降;旗叶中有GS1、GSx和GS2三种同工酶,其中GS2活性最高,GSx活性最低;籽粒仅有GS1。小麦花后旗叶和籽粒中GS和GS同工酶活性表现为60%FC>80%FC>40%FC,尤以旗叶GS2活性受影响最大。籽粒灌浆高峰前期,旗叶中可溶性蛋白含量表现为60%FC>80%FC>40%FC,随后表现为80%FC>60%FC>40%FC。籽粒中可溶性蛋白含量均表现为80%FC>60%FC>40%FC;60%FC处理的旗叶GS和GS2活性与可溶性蛋白含量呈显著正相关。籽粒产量和蛋白质含量均以60%FC处理最高,说明豫麦34生长中后期适宜的水分管理指标为田间最大持水量60%。     

不同氮肥处理条件下‘合丰55号’大豆主要叶部性状及蛋白质与产量的关系研究

为了研究不同氮肥处理条件下大豆叶部性状及品质与产量的关系,以‘合丰55号’大豆为试验材料,试验设置了4个不同氮肥处理,分别测定了开花后5个不同生育时期（R1、R3、R5、R6、R7期）的叶面积指数、叶绿素含量及各时期蛋白质含量。结果表明：‘合丰55号’大豆在5个不同生育时期的主要叶部性状均与产量呈正相关。各个氮肥处理的不同生育时期叶面积指数与产量的相关性达到显著或极显著水平;R1、R5期叶面积指数和全生育期的平均叶面积指数与产量达显著正相关,R6期与R7期达到极显著正相关;R5、R6期与全生育时期平均叶绿素含量与产量达显著正相关;蛋白质含量与产量成负相关关系,生育后期达到显著负相关。     

氮肥水平对杂交稻汕优63剑叶光合速率和RuBP羧化酶活性的影响

用低氮(LN)、中氮(MN)、高氮(HN)盆栽土培的杂交水稻汕优63为材料,测定其剑叶的光合速率、RuBP羧化酶含量及活性、可溶性蛋白和叶绿素含量的变化.结果表明:随着氮水平的提高,叶面积增大,气孔密度减少,RuBP羧化酶活性和光合速率增加.随着叶龄的增加,三个不同氮水平的叶片中RuBP羧化酶蛋白下降均先于可溶性蛋白的下降;HN组的光     

Differential Response of Two Wheat Genotypes to Nitrogen Supply. I. Ontogenic Changes in Laminae Growth and Photosynthesis

Two wheat genotypes viz. Uniculm 'gigas' (VI) and Kalyansona (V2) were raised till maturity with low (N1) and adequate (N2) nitrogen levels supplied at 30 and 120kg ha⁻¹, respectively. Laminae, numbering 1–8 on the main shoot, were examined for various parameters at weekly intervals from emergence through senescence. N1 resulted in gradual reduction in laminae growth from 5th leaf onwards with maximum effect on flag and penultimate laminae of both the genotypes. Chlorophyll concentration, soluble protein, rubisco concentration and rubisco activity in response to low N supply was reduced in the top two laminae in V2. Pn rate varied little with leaf position in wheat at adequate N supply. In V2, low N supply resulted in the reduction of laminae N content by about 25% with corresponding reduction in Pn rates in the penultimate and flag laminae. VI, in contrast, exhibited no significant change in leaf N concentration and hence maintained similar Pn rates at both levels of N supply throughout the ontogeny.
It is concluded that the two genotypes responded differently to N supply in relation to laminae growth and photosynthesis. Uniculm 'Gigas' (VI) responded to low N with large reduction in laminae size, adequately maintaining the metabolic constituents such as chlorophyll, soluble protein, rubisco and laminae N concentration and Kalyansona (V2), in contrast, responded with small changes in laminae size and greater reduction in synthesis and maintenance of the metabolic constituents.     

Effect of Water Stress on Pyruvaté, Pi Dikinase and Phosphoenol Pyruvate Carboxylase Activities in the Leaves of Two Cultivars of Sorghum (Sorghum bicolor L.)

The effect of withholding water on the specific activities of pyruvate, orthophosphate dikinase (PPDK EC 2.7.9.1.) and phosphoenol pyruvate carboxylase (PEPC, EC 4.1.1.31) was studied in two cultivars of Sorghum bicolor L. different in their sensitivity to water deficit. The drought sensitive cultivar ICSV 1063 and the more resistant cultivar MIGSOR were subjected to water deficit in controlled conditions. The results showed a decrease in both enzyme specific activities, higher for drought sensitive cultivar ICSV 1063, when leaf water potential (Ψ) was lowered to -2.3 MPa. Following rewatering, enzyme specific activities increased in both cultivars, with the increase being more significant in MIGSOR. Relative water content (RWC) decreased significantly for water-stressed ICSV 1063 cultivar, lower for MIGSOR and returned quickly to that of control plants upon rehydration. Net photosynthesis showed a decrease for water-stressed plants, higher for ICSV 1063. At minimal Ψ, net photosynthesis was completely inhibited, with the stomata being closed After rehydration, MIGSOR showed a better recovery in photosynthesis but never reached the initial values of day 0. Water stress had a striking effect, both on net photosynthesis by regulation of stomatal aperture and on PPDK and PEPC activities, although the enzymes were still active when photosynthesis ceased. Therefore the level of PPDK and PEPC activities may contribute to the limitation of photosynthetic carbon dioxide fixation.     

Seasonal Factors of Correlation Between Climatic Factors, Photosynthetic and Agronomic Traits in Maize

The dry matter accumulation and photosynthetic traits of upper leaves were studied twice weekly in 1983, under field conditions, for two early maturing maize cultivars. Analysis of correlation between climatic data and those traits were based on four week periods. Seasonal patterns of correlation coefficients were drawn by shifting the beginning of these four week periods from one sampling data to the next until four weeks before the end of the sampling period. Most traits were significantly correlated with climatic factors at one time or another; only those correlations which were of longer duration will be mentioned here. Net assimilation rate was positively correlated with maximum temperature during intensive leaf growth. The relative growth rate was closely correlated with photosynthetic photon irradiance (PPI) during the second half of June and with phosphofructokinase activity during the second part of July. The chlorophyll content showed a close and positive relationship with minimum temperature until the end of June and with PPI during most of August. The content of carotenoids was, for the most part, negatively correlated with climatic factors, the closest relationship existing with the PPI at the previous sampling date until the beginning of July. The activity of photosynthetic enzymes such as RuBP carboxylase, NADP malate dehydrogenase and PEP carboxylase was generally less closely correlated with climatic factors over longer periods. Patterns of correlation were remarkably similar for the two cultivars.     

哈密瓜叶色黄绿突变体Cmygl-1的高光合生理特性分析

叶色突变体是研究植物光合系统的结构和功能、叶绿素生物合成及其调控机制的理想材料。为了探究哈密瓜叶色黄绿突变体Cmygl-1的光合生理特性,以突变体、野生型近等基因系及F2遗传群体为试材,对叶色表型、农艺性状指标分别进行调查统计,并采用分光光度计法和试剂盒法分别测定叶绿素含量和酶活性,利用LI-6400光合仪和透射电镜分别进行光合特性测定和叶绿体结构扫描。结果表明,突变体叶色黄绿性状能够稳定遗传,受1对隐性等位基因控制;突变体叶片中光合色素含量显著降低,叶绿体膜较模糊,类囊体片层数减少,排列松散;突变体的净光合速率(Pn)、气孔导度(Gs)显著升高,胞间CO2浓度(Ci)和蒸腾速率(Tr)与野生型没有显著性差异,说明突变体的高净光合速率可能为非气孔因素;在低CO2浓度环境下,突变体净光合速率显著高于野生型,说明其具有较强的CO2固定能力;突变体遭受膜脂过氧化损伤,丙二醛(MDA)和过氧化氢(H2O2)含量显著升高;其过氧化物酶(POD)、抗坏血酸过氧化物酶(APX)活性和GSH/GSSG值均显著高于野生型,表明其能够激活自身抗氧化酶系统,清除体内过量的活性氧物质;突变体丙酮酸磷酸双激酶(PPDK)、磷酸烯醇式丙酮酸羧化酶(PEPC)和核酮糖-1,5-二磷酸羧化酶/加氧酶(Rubisco)等光合碳同化关键酶活性均显著高于野生型,可能是突变体净光合速率升高的原因。本研究结果为突变体高光合特性的分子调控机制研究奠定了基础。     

Development of a seedling screening test for predicting relative grain protein content in oats

Summary Growth room experiments were conducted to study associations of grain protein content with properties of seedling leaf sections of oats (Avena sativa L.) using (1) 10 cultivars differing genetically in grain % protein, and (2) 10 populations of a single high protien cultivar (Hinoat) differing phenotypically in grain % protein. These populations, which were derived from a nitrogen fertilizer experiment, had grain protein concentrations which varied over the whole range displayed by the high and low protein cultivars when the latter were tested in a conventional field trial.Seedling leaf % protein was closely associated with grain % protein in both (1) and (2). Chlorophyll content per unit leaf area and leaf dry weight per unit leaf area were significantly higher in the high than in the low protein cultivars, and were significantly higher in all the Hinoat populations than in the low protein cultivars.Excised seedling leaf sections were placed on filter paper moistened with 1 ppm kinetin solution and kept in the dark at 25°C. After 96 h chlorophyll content per unit leaf area was again significantly higher in the high protein cultivars and in all the Hinoat populations than in the low protein cultivars, and the consequent differences in leaf colour were then readily visible. Absolute amounts of chlorophyll lost per unit leaf area were similar in all cultivars and populations, but the low protein cultivars showed a greater proportional loss (as % of initial content). A colour scale was used to visually rate the senesced leaf sections. The visual rating allowed the rapid separation of the high and low protein cultivars, and there was no significant variation in the ratings of the Hinoat populations.It is suggested that this procedure may be useful in the early selection phases of protein breeding programs for screening large populations rapidly at the seedling stage to detect genetic differences in potential grain protein content.Contribution No. 438 from Ottawa Research Station.     

Reduced Sink Activity in Growing Shoot Tissues of Maize under Salt Stress of the First Phase may be Compensated by Increased PEP‐Carboxylase Activity

The effects of salt stress (100 mm NaCl for 6 days) on growing tissues (shoot apex, growing leaf segments, root tips) of young maize plants (Zea mays L. cv. Pioneer 3906) were investigated in comparison to an unsalinized control, focusing on assimilate supply from source leaves and the activity of sucrolytic enzymes in the sink tissues. The objectives were to test whether (i) phloem unloading in growing tissues is mainly symplastic, (ii) salinity reduces sink activity, determined either as sucrose synthase activity (indicator for the symplastic pathway) or as acid invertase activity (indicator for the apoplastic pathway), and (iii) PEP‐carboxylase activity is increased under salinity to compensate for reduced sink activity. For growing tissues of young maize shoots, it can be assumed that phloem transport of sucrose is mainly driven by symplastic unloading into the sink cells. In maize root tips, both, apoplastic and symplastic pathways, contributed to carbohydrate supply to the sink cells. The activity of acid invertase in growing shoot tissues was very low, and the alkaline invertase contributed less than 10 % to the cytoplasmic sucrolytic activity. Salt stress of the first phase (mainly osmotic stress) caused a significant inhibition of acid invertase activity in the growing leaf segments and in the root tips, which was also true for alkaline invertase activity in the root tips as well as for sucrose synthase activity in root tips and shoot apex. The decrease of sucrose synthase activity in shoot apex might be particularly detrimental for the plant growth, as this tissue with a high cell division rate relied entirely on cytoplasmic enzyme activities. Under salt stress, PEP carboxylase activity was significantly increased in growing leaves and the shoot apex of maize, whereas no significant effect was observed in the root apex. In conclusion, PEP carboxylase can have an anaplerotic function supporting the demand for metabolites in growing shoot tissues of young maize plants under salt stress. In root tips, an additional supply of organic acids to the tricarboxylic acid cycle is probably not needed, as sucrolytic sink activity, which was high even under saline conditions, can meet the demand of the sink cells.     

超高产夏玉米花粒期不同部位叶片衰老与抗氧化酶特性

为探讨超高产玉米叶源衰老特征, 揭示其抗氧化关键酶及膜脂过氧化特性, 为玉米衰老调控和高产栽培提供依据, 本研究在大田条件下, 以我国创高产纪录的夏玉米为例, 从单株水平上对高产纪录试验(EHYR)和普通生产田(MCFF)玉米叶片衰老及抗氧化酶特性比较表明, EHYR产量达19 349 kg hm^-2, 是MCFF的2.28倍。MCFF和EHYR叶片分别在开花后30 d和50 d进入速衰期, MCFF叶片衰老比EHYR提前20 d;速衰期EHYR叶面积降幅比MCFF低5.7%。EHYR在籽粒灌浆后期, 中上部叶片净光合速率较高, 可溶性蛋白含量明显高于MCFF, 而MDA含量则维持较低水平。在叶片衰老过程中, 自开花后20 d开始, EHYR上部和中部叶片SOD活性较高, 下部叶片则以SOD、POD和CAT三者活性较高;MCFF仅中部叶片POD和CAT活性较高。EHYR叶片衰老程度与CAT活性极显著负相关, MCFF叶片衰老与SOD和POD活性显著负相关, 且二者叶片衰老进程中SOD、POD、CAT的直接作用大于间接作用。与MCFF相比, EHYR叶片除具较高SOD和POD活性外, 在籽粒灌浆后期同时保持较高CAT活性和可溶性蛋白含量是降低膜脂过氧化程度, 延缓叶片衰老的重要原因。开花后20 d是EHYR与MCFF叶片衰老出现差异的生理临界点, 因而在此时期之前调控更有利于延缓衰老。