关于光呼吸与光合作用关系的研究——Ⅶ、光呼吸是伴随光合作用发生的过程

测定水稻、小麦、棉花等C_3植物和玉米、高粱等C_4植物的光合与光呼吸强度,研究不同处理对光合与光呼吸的影响。植物的光呼吸是与光合作用伴随发生的。强光、高氮等有利光合作用的因素能促进光呼吸;DCMU、叶片失水等抑制光合作用的因素也降低光呼吸。在光合滞后期中,光合强度与光呼吸强度平行上升。在同类植物中,光呼吸强度与光合强度之间有较稳定的比值,C_3、C_4植物的光呼吸占光合分别为30—35％和4％。     

Simultaneous measurements of quantum yield and CO2 uptake for the assessment of non-assimilative electron flow in tree leaves

Using attached and detached leaves ofAcer palmatum Thunb. andRhaphiolepsis umbellata Makino, pulse-modulated chlorophyll fluorescence and CO₂ exchange were measured. Quantum yield of photosynthesis was determined from the fluorescence parameter(Fm′−Fs)/Fm′, where (Fm′−Fs) was defined as the difference between steady state chlorophyll fluorescence (Fs) and maximum fluorescence (Fm′) elicited by a saturating light pulse. The rate of electron transport through photosystem II (total electron flow) was calculated from the product of quantum yield andA (PFD), whereA is the rate of absorbed photons as given by leaf absorptance, and PFD is the photon flux density at the leaf surface. The rate of electron transport dependant on CO₂ uptake (assimilative electron flow) was calculated from the gross photosynthetic rate in a leaf. The difference between the rates of total and assimilative electron transport was denoted as the rate of non-assimilative electron transport which depends on photorespiration and oxygen reduction. Available data provided quantitative information on the rate of non-assimilative electron flow in intact leaves. When leaf photosynthesis ofA. palmatum was measured under sunlight, the rates of total and assimilative electron transport were determined to be approximately 900 and 150 μmol equiv. e/mg Chl·h, respectively. The difference (750 μmol equiv. e/mg Chl·h) was attributed to the activity of non-assimilative electron flow. The ratio of total to assimilative electron flow was found to increase gradually with rising in irradiance. The results suggest that non-assimilative electron flow occurred at much higher rate than assimilative electron flow at high irradiance. Implications of the results are briefly discussed in relation to photosynthesis limitation in tree leaves.     

外源一氧化氮对铝胁迫下烟草叶片光能利用和光保护系统及活性氧代谢的影响

以云烟100(耐铝)和云烟105(铝敏感)为材料,采用水培法研究外源一氧化氮(NO)对铝胁迫下烟草植株生长、叶片活性氧含量、光合特性、叶绿素荧光参数、光呼吸和抗氧化酶活性的影响。结果表明,铝胁迫显著降低了烟草叶片叶绿素含量、净光合速率(Pn)、最大光化学效率(Fv/Fm)、PSII光合电子传递量子效率(FPSII)和光化学猝灭系数(q P),提高了反应中心PSII过剩激发能,从而导致叶片超氧阴离子(O_2·)和过氧化氢(H_2O_2)含量升高,植株生物量下降。外源NO可显著提高铝胁迫下烟草叶片叶绿素含量、Pn、Fv/Fm、FPSII、q P和植株生物量,降低反应中心PSII过剩激发能和叶片O_2·、H_2O_2含量,且云烟105变化幅度高于云烟100。此外,外源NO还显著提高了铝胁迫下烟草叶片非光化学猝灭系数、光呼吸速率、超氧化物歧化酶和抗坏血酸过氧化物酶活性,说明NO可通过提高烟草叶片光化学反应能力、热耗散、光呼吸以及抗氧化酶活性来降低反应中心PSII过剩激发能,防止或清除叶绿体内产生的活性氧,缓解铝对烟草的毒害,这种缓解效应在敏感基因型云烟105中表现更明显。     

吲哚乙酸对烟草叶片光合作用和光呼吸的影响

烟草叶面喷施10～100ppm的IAA,光合、光呼吸、CO_2补偿点、乙醇酸合成量、以及RuBp羧化酶/加氧酶和乙醇酸氧化酶活性均提高,而且均随IAA浓度的增加而增高。抗生长素三碘苯甲酸抑制光合和光呼吸,降低CO_2补偿点,降低BuBp羧化酶和乙醇酸氧化酶活性。草甘膦亦降低光合、光呼吸强度和乙醇酸氧化酶活性。亚胺环己酮和放线菌素D亦降低叶片乙醇酸氧化酶活性,并消除由IAA引起的酶活性增强。认为IAA通过提高RuBp羧化酶活性而增强光合作用;通过增加乙醇酸合成和提高乙醇酸氧化酶活性而提高光呼吸。     

氮素营养对冬小麦光合与光呼吸的调节

以冬小麦扬麦4号为材料,采取不同的施氮水平处理,研究氮素营养对冬小麦光合与光呼吸的调节.用氧电极测定RuBPOase活力.用~(14)C同位素测定RuBPCase活力,用红外线CO_2气体分析仪测定光合和光呼吸强度.结果表明:这些代表整体和酶学水平等几个不同层次的光合参数均随氮素水平的不同而有显著差异,且这些光合参数之间呈极显著的正相关.另外还观察到,光呼吸比光合作用对氮的反应敏感性更强.本文对氮与光呼吸的关系及光呼吸对碳氮代谢的调节机理进行了讨论.     

小冠开心形和细型主干形‘玉露香’梨光能截获与光合作用差异

小冠开心形和细型主干形是黄土高原梨树生产中的主要树形模式。为阐述这两种树形对冠层光能截获和叶片光合功能的影响,以山西芮城县4年生的‘玉露香’梨为试材,2017年和2018年连续两年测定了冠层截获的光合有效辐射PAR、叶片光合的光响应特性、荧光淬灭动力学特性以及光午休期间叶片的热耗散特性和光呼吸。结果表明:小冠开心形冠层不同方位和不同时刻截获的PAR均高于细型主干形,平均提高47.6%;与细型主干形相比,小冠开心形叶片光响应的最大净光合速率P_nmax,p与光饱和点LSP显著升高;光合碳同化过程的3个限制因子中,磷酸丙糖利用速率V_tpu对冠层光环境变化最敏感。正午强光胁迫下,小冠开心形叶片光呼吸速率P_r与总光合速率P_g的比例(P_r/P_g)比细型主干形叶片提高58.5%,NPQ中可恢复组分r(qE)提高了8.9%,而不可恢复组分r(qI)降低了75.0%。两种树形相比,小冠开心形梨树冠层可截获更多的光能,叶片的光合能力更强,强光胁迫时能够通过更高效的热耗散和光呼...     

Effect of Leaf Sugar and Starch Concentrations on Apparent Photosynthesis in Alfalfa

Rates of apparent photosynthesis (AP), dark respiration, photorespiration, mesophyll resistance, and concentrations of soluble starch, sugars, chlorophyll and nitrogen were measured in alfalfa leaves ( Medicago sativa L.) grown under high or low light levels in an attempt to evaluate the effect of nonstructural carbohydrate concentration on net CO₂ assimilation.
Leaf N and chlorophyll levels of high light plants exceeded those of low-light plants. Constant light increased both starch and sugar levels in low-light plants, but had little effect on high-light plants. Rates of AP declined in low-light plants upon transfer to constant light conditions, apparently due to increases in stomatal and mesophyll resistance. Leaf starch levels were negatively correlated (P > 0.05) with rates of AP and positively correlated with mesophyll resistance in both groups of plants but leaf sugar content was not correlated with either AP or mesophyll resistance.
Starch and sugar levels of high-light plants declined substantially upon transfer to constant darkness, while low-light plants were less affected. Rates of AP declined in both groups of plants due to increases in both mesophyll and stomatal resistances. Neither sugar nor starch levels were correlated with AP or mesophyll conductance in this treatment.
The data support the hypothesis of feedback inhibition of photosynthesis, mediated through an increase in mesophyll resistance, which is associated with high levels of starch in the leaves.     

植物光呼吸分子机制研究进展

光呼吸是植物的绿色细胞在光照下吸收O2释放CO2的反应,光呼吸强弱是影响C3和C4植物光合效率高低的重要因素。对光呼吸的分子机理研究是光合作用研究的热点之一。本文就光呼吸的代谢途径、光呼吸基因表达调控及光呼吸突变体的筛选等方面的研究进展进行了阐述,对光呼吸的生物学功能进行了探讨,并对光呼吸领域的发展进行了展望。     

植物激素对咖啡幼苗叶片乙醇酸氧化酶活性及光合作用的影响

咖啡幼苗叶片提取过程中,由于单宁等次生物质存在,使乙醇酸氧化酶(GAO)容易失活,加入40％(w/w)PVP(聚乙烯吡咯啉酮K值27～33)作保护剂,GAO活性恢复并达到最大。用不同浓度的各种激素对咖啡幼苗叶片处理时,GAO活性都受到了抑制,其中IAA,GA_3,CTK和乙烯利的抑制随浓度增加而增加,抑制效应的顺序是100ppm>50ppm>10ppm,而ABA却相反,随浓度增加而减弱。相同浓度的各种激素对GAO活性及光合作用的影响,表现出相似的规律性,在处理12小时后开始发生抑制,随着时间的推移,GAO活性逐渐下降,到一定时间后逐渐回升或在回升线上波动,到处理144小时,基本上恢复到对照水平。激素对GAO与光合作用的抑制,表明了光呼吸与光合作用存在着伴随关系。