Diurnal Changes in Photosynthesis in Wheat Under Different Source-Sink Relationships

The effect of alteration in source-sink ratio by defoliation and ear removal on diurnal changes in photosynthesis was examined in wheat var. Kalyansona. The photosynthesis rate was maximum during initial few hours in the forenoon and decreased towards evening. The increase in sink demand for a particular leaf by excising other sources leaves, sustained higher rate of photosynthesis during the day. On the other hand de-eared plants where sink demand was decreased by removal of main shoot ears and all the tillers, photosynthesis rate showed a more rapid decline towards evening, although, the photosynthesis rates were more or less similar to control plants in the morning. These results indicate the influence of sink demand on sustenance of photosynthesis during the day.     

库大小对水稻不同叶位叶片氮代谢的影响

采用去穗与疏花方式调节库大小，研究了对水稻不同叶位叶片氮代谢的影响。去穗或疏花后，已完成发育的源叶片，尤其是顶4叶，蛋白质合成重新旺盛，蛋白氮含量提高，出现了类似于生长库的氮代谢特征。水稻叶片的酸性转化酶活力可反映其蛋白质合成能力，据此可判断叶片是属于氮素供应源还是氮素接受库。研究证实下位叶的氮代谢     

土壤干旱对小麦叶片渗透调节和光合作用的影响

本文研究了土壤干旱对小麦叶片渗透调节和光合作用的影响.小麦叶片水势、相对含水量、饱和渗透势、光合速率、蒸腾速率和气孔导度随土壤干旱程度加剧呈现出先缓降后陡降的趋势,其变化的土壤相对含水量阈值相同.小麦旗叶的渗透调节能力约为0.5MPa,不同叶位叶片渗透调节能力不同,其强弱顺序为旗叶>倒二叶>倒三叶.干旱使叶片膨压丧失时的渗透势从正常水分处理的-1.61MPa降到-2.33MPa,弹性模量从5.74MPa增加到6.35MPa.干旱条件下的光合速率、气孔导度、气孔限制值和叶片光合放氧能力都下降,而细胞间隙CO_2含量增加,说明光合速率的降低是非气孔因素即叶肉细胞光合活性限制的结果.     

HgCl2短时处理对蚕豆叶片光合作用的效应

以不同浓度HgCl₂溶液涂抹蚕豆(Vicia faba L.)叶片30 min后, 测定进入叶片组织的汞含量、叶片的气体交换和叶绿素荧光。随着外施HgCl2溶液浓度的增大, 进入叶片组织的汞含量增加。当HgCl₂溶液浓度高于10 mg L^-1时, 处理显著抑制蚕豆叶片的净光合速率(P_n)和表观光合量子效率(AQY), 且随着浓度增加, 抑制程度也加强。同时, HgCl₂溶液处理能够显著降低PSⅡ光量子产量(DF/ F_m’)和表观光合电子传递速率(ETR), 增加叶片的叶绿素荧光非光化学猝灭(NPQ)。 结果表明, 低浓度HgCl₂短时间处理导致蚕豆叶片P_n降低的主要原因是由于HgCl₂抑制了光合电子传递过程。     

烯效唑延缓小麦成熟期间叶片衰老的效应

１９８９～１９９２年田间与盆栽试验，研究烯效唑对小麦成熟期间旗叶及下二叶等三片功能叶衰老的延缓作用和增产效果。研究表明：１．烯效唑延缓小麦成熟期间功能叶片的衰老，表现在叶片细胞电解质渗漏率降低，超氧物歧化酶活性增高，丙二醛积累减少；２．烯效唑对离休旗叶片有保绿作用；于小麦齐穗期喷施２０～４０×１０－６，烯效唑药液７５０ｋｇ／ｈｍ２，可提高小麦千粒重３～４ｇ，增产１２％～１６％。     

种植密度对烤烟不同部位叶片光合特性及其同化积累的影响

选用云烟87,研究4种种植密度(16 665、15 150、13 875和12 825株 hm^-2)对烤烟下、中、上3部位叶片光合及其同化物的影响。结果表明,叶片净光合速率(P_n)、比叶重以及碳水化合物总量在成熟期(移栽60 d以后)明显表现出密度效应。随着群体生育进程的推进,密度对3个指标的影响程度有增大趋势。降低种植密度可以减小叶片P_n下降率,延缓光合功能的衰退,延长同化产物的积累时间。下部叶除12 825株 hm^-2外,其他3处理均未出现光合“午休”现象; 而上部叶片均出现“午休”现象; 较高种植密度能够减轻中部叶片“午休”的程度。在15 150株 hm^-2的种植密度下,中部叶片日光合总量较高,光合产物也达到较高水平,叶片光合作用和蒸腾作用也达到最为协调的状态,有着较高的水分利用率。     

Leaf thickness and response of leaf photosynthesis to water stress in soybean varieties

Summary A comparative study of photosynthetic response to soil moisture was conducted with soybean varieties (Harosoy, Norin No. 1 and Hogyoku). When the plants were grown in May before the rainy season under a high radiation level, per unit leaf area the photosynthetic rate of Harosoy leaves was significantly higher throughout the entire range of soil water potentials and leaf water potentials than that of Norin No. 1 leaves. The high photosynthetic rate of Harosoy under non-stress conditionsaand mild water stress was associated with both the high specific leaf weight and the high leaf areal nitrogen content. The photosynthetic response of the Harosoy leaves developed during rainy season under a low radiation level, however, was similar to that of Norin No. 1; no significant difference was observed between these two varieties in the specific leaf weight and in the leaf areal nitrogen content.On the other hand, Hogyoku cultivated especially along the footpaths between the paddy field was very sensitive to water stress, closing the stomata at higher soil water potentials. Under non-stress conditions, as compared with per unit leaf nitrogen content, however, Hogyoku performed higher leaf photosynthesis even with a thinner leaf than Harosoy.     

Photosynthesis and Dry Matter Production in T. monococcum and T. aestivum Wheat in Response to Ear Removal

The photosynthesis, shoot formation, leaf area development and dry matter production were examined in control and de-eared plants of T. monococcum var. G 1372and T. aestivum var. Sonalika. The removal of ears decreased the diurnal maintenance of photosynthesis and consequently, the dry matter production in Sonalika but not in G 1372. There was a considerable growth of alternative sinks such as shoots and roots when ear sinks were removed. This alternative sink capacity of de-eared plants seemed to have compensated for limited sink demand of ears in G 1372but could not entirely compensate for the more efficient grain sink in Sonalika. The diploid wheat produced more dry matter than the hexaploid wheat in the pre-ear emergence period and less in the post-ear emergence period. In the preear emergence period, the difference in dry matter appeared to be mostly because of the difference in duration to ear emergence. During the post-ear emergence period, the lower dry matter in G 1372seemed to be owing to a rapid decrease in photosynthesis rate after anthesis because of the lower sink capacity of its grains.     

Non-destructive Limits to Seed Growth and Leaf Protease Activities in Nodulating and Non-nodulating Soybean Isolines

Leaf senescence leads to a progressive decline in the photosynthetic competence of the leaf. This paper describes some effects of source:sink imbalance on leaf protein catabolism and senescence in soybean. We manipulated pod growth by restricting 100 or 50 % (PR-100 or PR-50, respectively) of young pods at the R4 stage in plastic drinking straws. This effectively reduces final seed mass without interrupting the vascular connections of pods. Nodulating (NOD+) and non-nodulating (NOD−) isolines of the 'Clay' soybean were grown in drainage lysimeters and three pod-restriction (PR) treatments were compared. Pod restriction decreased seed biomass per plant as a result of lower individual seed mass, which was only partially balanced by the increase in seed number. The nitrogen concentration in seeds remained unchanged in NOD+ plants, while it increased with the degree of sink restriction in seeds of NOD− plants. Leaf soluble protein, CO₂ exchange rate and seed nitrogen content were consistently lower in NOD− plants; the leaf protein level remained stable with time in PR-100 plants, decreased for PR-50 and dropped for controls. Endoprotease (HBase) and carboxypeptidase (CPase) activities were significantly lower in leaves from PR-100 plants, while aminopeptidase activity was enhanced, indicating a de novo synthesis of leaf protein. This is consistent with the reported accumulation of vegetative storage proteins (VSPs) in soybean and other legumes after moderate or severe sink reduction. Thus, small modifications of the source:sink ratio such as those obtained by the non-destructive PR technique have an impact on leaf protein catabolism. Nodulating and non-nodulating soybean isolines showed similar responses to PR in terms of leaf senescence initiation and progression, but the rate of the processes appear to be largely influenced by plant N status.     

关于玉米光合作用与叶片水分利用效率关系的研究

研究分析了玉米１７个自交系和１１个杂交种单叶光合速率，蒸腾速率和叶片水分利用效率。结果表明，玉米自交系或杂交种间单叶ＰＨ、ＴＲ和ＷＵＥ存在着显著差异。ＷＵＥ与ＰＨ呈极正相关关系，且较ＷＵＥ与ＴＲ的关系更密切。玉米单叶的ＷＵＥ、ＰＨ、ＴＲ值会随着叶位、生育时期、光辐射强度、种植密度不同而不同，也会由于源库比改变、植株个体 间差异而变化。ＷＵＥ和ＰＨ之产是回归直线的斜率随生率的推延而增大，但几乎不受源     

植株叶片蔗糖、淀粉积累与其降解酶活性关系研究

不同植物功能叶片淀粉、蔗糖积累及酸性转化酶、淀粉酶活性均存在显著差异。依叶片蔗糖与淀粉积累量比值可大体将测定的28种植物划分为以积累淀粉为主的粉叶植物，以积累蔗糖为主的糖叶植物和介于两者之间的中间类型植物。三类植物功能叶片淀粉积累量与淀粉降解酶活性均无显著相关，但糖叶及粉叶植物叶片蔗糖积累量与酸性转化     

金叶榆不同叶位叶片呈色生理机制研究

通过测定金叶榆不同叶位叶片的色素含量和光合生理参数,旨在研究其叶片的呈色生理机制。结果表明,叶绿素a、b含量从顶梢向下逐渐升高,类胡萝卜素、花青素含量及色差参数L、a、b值逐渐降低;净光合作用速率显著升高,叶位7以下的叶片高达12μmolCO2/(m²·s)以上,而顶梢叶位1没有光合产物积累;单位面积进入用于电子传递的量子产额ETO/CS提高,光量子的热耗散比率DIO/CS降低;最大光量子效率提高,叶位9以下的叶片Fv/Fm在0.8以上;叶位12、11的性能指数、光合驱动力明显高于上部的叶片,与对照白榆没有明显差异。试验发现,金叶榆叶片色彩与类胡萝卜素含量成极显著正相关关系,叶片色彩受光照条件和光合作用状态调控,说明金叶榆叶片色彩是一种生态表现型。     

氮素水平对不同基因型小麦旗叶光合特性和子粒灌浆进程的影响

在池栽条件下，研究了不同施氮水平对强筋小麦8901和弱筋小麦1391生育后期旗叶叶绿素含量、光合速率、灌浆速率和产量的影响。结果表明，两品种表现为随施氮量的增加，叶绿素含量、光合速率都有增加的趋势，但是过量氮肥又使它们降低。在本试验条件下，两品种均以中氮处理(240kg／hm^2)光合速率大，灌浆进程合理，产量水平高。研究发现，强筋和弱筋小麦生育后期叶光合特性和子粒灌浆进程差异显著；旗叶光合速率和叶绿素含量及子粒产量呈正相关。     

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.     

棉花源库调节对铃叶光合产物运输分配的影响

通过早打顶去边心和人工剪叶,研究了减库或减源对铃、叶光合产物运转分配的影响。结果表明,当棉铃发育受减库调节时,铃体积增大,铃重提高,而且对高品质棉科棉1号影响较大;花后40 d科棉1号叶片可溶性糖和淀粉含量分别比对照增加41.0%和4.1%,常规棉苏棉15分别比对照增加14.8%和77.3%;花后30日铃对位叶标记24 h后¹⁴C光合产物的输出,科棉1号增加17.6%,苏棉15增加6.8%;棉铃光合产物输入率,科棉1号比苏棉15增加3.6%;此外,铃柄韧皮部中全氮、可溶性糖增加;棉铃发育受叶源限制调节时,铃体积减小,铃重降低,而且对苏棉15影响大;叶片中可溶性糖和淀粉含量减少,全株去3/4叶处理花后40 d科棉1号分别比对照减少8.7%和28.4%;苏棉15分别减少23.6%和32.2%。叶片¹⁴C光合产物输出率和棉铃¹⁴C光合产物输入率均降低,其中又以苏棉15下降幅度大。铃柄韧皮部中全氮、可溶性糖也相应下降。因此,通过技术手段调节源库,可以促进高品质棉叶片光合产物向棉铃输送,进而提高铃重。     

水分胁迫下葡萄糖对小麦幼苗光合作用和相关生理特性的影响

以15%聚乙二醇(PEG-6000)模拟水分胁迫,以不同浓度外源葡萄糖(Glc)处理小麦幼苗,探讨外源Glc对水分胁迫下小麦幼苗生长发育和光合特性的影响。结果表明,水分胁迫显著降低了小麦叶片水势和光合作用,抑制植株的生长,而水分胁迫下外源Glc处理能明显增加叶片水势和光合色素含量,并使水分胁迫和水分胁迫后复水处理条件下,小麦幼苗叶片的净光合速率(P_n)、气孔导度(G_s)胞间CO₂浓度(C_i)和叶片水分利用效率(WUE)显著升高,而使蒸腾速率(T_r)下降。同时,外源Glc处理显著提高了水分胁迫下叶片中可溶性糖和脯氨酸的积累,促进不定根和侧根的生长,植株干重比单一干旱处理提高14.32%~40.39%。由此表明,水分胁迫下外源Glc通过促进小麦根系生长和提高叶组织的渗透调节能力,改善叶片的水分状况,提高了叶片的光合功能,促进小麦幼苗的生长,降低了水分胁迫对小麦幼苗生长的抑制作用。     

田间密植诱导抽穗期玉米叶片衰老时的光合作用机制

为理解田间密植是否诱导抽穗期玉米叶片衰老以及衰老叶片的光合作用规律和机制,本研究以玉米"先玉335"为材料研究了抽穗期栽培密度对穗位叶和穗下第4叶的光环境、比叶重、氮素含量、叶绿素含量、气体交换以及叶绿素荧光诱导动力学的影响。结果表明,随着密度的增加玉米冠层内的光强大幅降低,尤其穗下第4叶;穗位叶和穗下第4叶的比叶重降低。同时,穗位叶和穗下第4叶的氮素含量和叶绿素含量均随栽培密度增加而下降。不同栽培密度下穗位叶荧光诱导动力学曲线(OJIP)未发生明显改变,而高密度下穗下第4叶OJIP的J和I相的相对荧光产量较低密度有提高趋势。高密度下,穗位叶和穗下第4叶叶片的光合速率、气孔导度和蒸腾速率均降低;不过,穗位叶胞间CO2浓度降低,穗下第4叶胞间CO2浓度增加。我们认为,田间密植条件下异质性光环境可以迅速诱导抽穗期玉米冠层下部叶片(如穗下第4叶)衰老;该过程中,光合作用的限制因素不是光能吸收和电子传递,而可能是碳同化。     

减库对大豆叶片碳代谢的影响

植物的碳代谢过程与植株生长和产量形成密切相关,是受源库关系影响最明显的生理过程之一。研究减库对大豆叶片碳代谢的影响,可为明确源库关系失衡导致的减产机理研究提供理论依据。以早熟大豆品种苏豆13为材料,于2019年和2020年在江苏省农业科学院大豆试验站进行池栽试验,在大豆R4期设置减库处理(去除全部豆荚、去掉1/2豆荚和全部种子损伤处理),以正常植株为对照,研究减库对大豆碳代谢的影响。结果表明,减库处理延缓了叶片衰老和脱落,导致叶片持绿。减库处理显著抑制了短期内的净光合速率(Pn),但是未影响初始羧化速率(a)。Pn降低主要受气孔限制,随时间延长,光合抑制作用逐渐减弱并转为促进作用,在生育后期,减库处理的叶片仍能保持相对较高的a、蔗糖磷酸合成酶(SPS)、蔗糖合成酶(SuSy)和酸性转化酶(SAI)活性及光合色素、可溶性糖、淀粉、蔗糖和果糖含量,利于维持相对较高的光合性能。减库处理导致更多的光合产物向营养器官分配,茎、叶片和叶柄在一定程度上成为新的库器官,利于生育后期的叶片光合产物输出并保持相对较高的碳代谢水平。去除全部豆荚和种子损伤处理延缓叶片衰老和脱落、光合性能和碳代谢水平降低的作用...     

棉花源库比对中、下部果枝叶生理活性及铃重的影响

以转基因抗虫杂交棉中棉所29(CCRI29)为材料,通过去叶和去蕾处理,研究改变源库比对大田棉花中、下部果枝叶生理活性的影响。结果表明：减库处理可以提高中、下部果枝叶片中蛋白质的含量,促进后期果枝叶中叶绿素的合成,延长叶片功能期。减源处理促进中、下部果枝叶生长前期果枝叶中叶绿素含量,表现出暂时性的超补偿效应,但是在果枝叶生长后期,叶绿素含量快速下降;并且减源处理不利于叶片中蛋白质的合成。提高源/库比、降低源/库比均降低了中、下部果枝叶中SOD和POD活性,对MDA含量的影响为：减源＞CK＞减库。源库比例的改变影响叶片的寿命和功能,改变棉花源库比,打破了源库平衡,其叶片的生理活性也会发生相应变化。受源器官生理特性变化的影响,不同处理单铃重差异较大,表现为：减库＞CK＞减源。     

不同磷效率小麦品种的光合特性及其生理机制

以典型的不同磷效率小麦品种为材料,对磷低效（L）、吸收高效（Ha）和利用高效（Hu）品种的光合特性及其生理机制进行了研究。随着叶片生长进程,供试品种旗叶CO₂传导参数气孔导度（G_s）、叶肉导度（G_m）和碳酸酐酶（CA）活性,春4叶和旗叶叶绿素含量（Chl）、可溶蛋白含量（SP）、叶绿体无机磷（P_i）浓度和Mg²⁺-ATPase活性以及光合速率（P_n）均不断降低。光合暗反应关键酶RuBPCase活性则以叶片全展后15 d较高,叶片全展时次之,全展后30 d最低。在缺磷条件下,春4叶和旗叶各测定时期上述参数均以L较低,Ha和Hu较高。表明磷高效小麦品种（Ha和Hu）叶片光合碳同化作用的相对提高,是其光合器官捕光能力较强、光合作用的气孔限制和非气孔限制程度较低和暗反应速率较高综合作用的结果。叶片全展后15 d的RuBPCase活性及单位RuBPCase蛋白的比活性较叶片全展时有所增加,暗示着在叶片老化过程中或在磷营养逆境胁迫条件下,植物体内部分代谢酶类,如RuBPCase,存在着一定的自我调节和保护机制以维持自身功能。