Relationships between D1 protein, xanthophyll cycle and photodamage-resistant capacity in rice (Orysa sativa L.)

Relationships between D1 protein, xanthophyll cycle and subspecific difference of photodamage-resistant capacity have been studied in O. japonica rice varieties 02428 and 029 (photoinhibition-tolerance) and O. indica rice varieties 3037 and Palghar (photoinhibition-sensitivity) and their reciprocal cross F1 hybrids after photoinhibitory treatment. It was shown that PSⅡ photochemical efficiency (Fv /Fm) decreased, and xanthophyll cycle from violaxanthin (V), via anaxanthin (A), to zeaxanthin (Z) was enhanced and non-photochemical quenching (qN) increased accordingly in SM-pretreated leaves of rice when the synthesis of D1 protein was inhibited, and that there was a decrease in qN and, as a result, more loss of D1 protein and a big decrease in Fv /Fm in DTT-pretreated leaves when xanthophyll cycle was inhibited. O. japonica subspecies had a higher maintaining capacity of D1 protein and a decrease of Fv /Fm in a more narrow range, and exhibited more resistance against photodamage, as compared with O. indica subspecies. The above physiological indexes in reciprocal cross F1 hybrids, though between the values of their parents, were closer to maternal lines than to paternal lines. Experimental results support the concept that the turnover capacity for D1 protein is an important physiological basis of photoinhibition-tolerance, and will provide the physiological basis for selection of the photoinhibition-tolerant parents and develop a new approach to breed hybrids with high photosynthetic efficiency.     

弱光和Tris处理条件下PSⅡ放氧核心复合物的损伤

弱光条件下(120μmol·m-2·s-1)用Tris(0.8mol/L,pH6.5～10.0)处理具有放氧活性的PSⅡ核心复合物,可引起33kD锰稳定蛋白的释放和锰复合物的破坏,并导致核心复合物的结构发生明显的改变.温和电泳、SDS-PAGE和双向电泳分析表明,主要是PSⅡ核心复合物的二聚体和单体减少,并且复合物部分解体;除反应中心D1和D2蛋白外,核心天线CP43和CP7的量也减少,33kD锰稳定蛋白要发生降解.避光时,PSⅡ核心复合物不受影响.     

Effect of calcium ions on the secondary structures of photosystemⅡ and its relations with photoinhibition

Calcium ions play an important role in the oxygen_evolving process of photosystem Ⅱ as demonstrated in many experiments. The changes of the secondary structures of PS Ⅱ induced by the depletion of Ca 2+ were reported. The results indicated that the removal of Ca 2+ led to the transition of α helix to turns and sheet structures. While Ca 2+ was re_added to the media, only the structures changed to turns could be recovered. The protein conformational changes of PS Ⅱ during the donor side photoinhibition induced by the depletion of Ca 2+ were also studied. This showed that the protein conformational changes differed between the control and Ca 2+ _depleted samples in a short period of illumination (within 10 min). However, the changes became similar when the illumination time was increased.     

Effect of Mn cluster on the formation of superoxide radicals in photoinhibition of photosystem Ⅱ

To further realize the action of superoxide radicals (O₂^{− .}) in photoinhibition of photosystem Ⅱ (PSⅡ), we employed 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as a spin trap, associated with EPR spectroscopy, to study the effect of illumination time on O₂^{− .} formation during high light photoinhibition in PSⅡ membranes and Mn-depleted PSⅡ membranes. Results indicated that the removal of Mn cluster from PS
membranes has a strong influence on the dynamics of superoxide formation. The relative mechanism was also discussed. These novel findings may further promote the studies of the structure and function of PSⅡ and the mechanism of photoinhibition.     

光周期对葛仙米生长和光合系统活性的影响

通过设置光暗比(L∶D)24h∶0h、12h∶12h和8h∶16h三个光周期处理组,对葛仙米(Nostoc sphaeroides Kutzing)依次开展了三个批次的培养,测定光周期对葛仙米生长和光合活性的影响.结果表明,24h连续光照对葛仙米生长具有显著抑制作用,不适合应用于葛仙米的长期连续批量培养中.3个光周期处理组中,葛仙米叶绿素荧光Fv/Fm在第一个培养批次中降低,但是很快都在第二个和第三个培养批次中得到缓和.葛仙米PS捕光天线色素含量的变化表明,葛仙米能够通过下调该色素的含量来降低较长光照对葛仙米光合系统的光抑制和破坏,从而获得较高的光合作用效率.     

短时强光对绿萝快速叶绿素荧光诱导动力学特性的影响

本研究以室内培养的阴生植物绿萝（Epipremnum aureum）为实验材料,将绿萝于7月晴天上午8:30-9:30置于室外全光照环境下(光照度21000~34500 lux)处理1.0 h,然后移入室内弱光(最大光照度3600 lux)恢复48 h。于处理不同时期对绿萝叶片进行快速叶绿素荧光诱导动力学曲线的测定,通过比较叶片快速叶绿素荧光诱导动力学特性的变化,以探索绿萝叶片光合机构对短时强光胁迫的响应特征。结果表明：短时强光胁迫导致绿萝叶片光抑制（Fv/Fm）发生,并引起叶片光合性能指数（PI_ABS）下降,室内弱光有利于Fv/Fm和PI_ABS的恢复,但PI_ABS恢复慢于Fv/Fm。短时强光胁迫并未对PSII供体侧放氧复合体（OEC）和PSI反应中心产生影响,但造成PSII反应中心不可逆失活。短时强光使得叶片单位面积内有活性的PSII反应中心数量（RC/CS）下降,从而降低了叶片单位面积吸收的光能（ABS/CS）、捕获的光能（TRo/CS）和进行电子传递的能量（ETo/CS）,且其影响在短时间内难以恢复。短时强光虽然降低了捕获光能用于电子传递的量子产额（φEo）,但诱导了PSII受体侧PQ库容量（Sm）的增大,这有利于维持光合电子传递,是绿萝对短时强光的应急适应性反应。     

济南市校园6个绿化树种光合荧光特征比较初探

利用GFS-3000便携式光合仪、Mini-PAM便携式调制叶绿素荧光仪，研究了6种济南市校园绿化树种的光合荧光特征. 结果表明，龙爪槐和日本樱花净光合速率日变化曲线为单峰型，其他4种为双峰型曲线，双峰型曲线的光合午休由非气孔限制因素引起；龙爪槐和日本樱花单峰型的净光合速率对应着双峰型的气孔导度和蒸腾速率，在减少水分丧失的同时不降低同化能力. 随光照的增强，6个树种的最大荧光产量、有效量子产量均下降，非光化学淬灭上升，但物种间各参数变幅不同. 对电子传递速率的光响应曲线进行拟合，分析6个树种对光能的适应和利用能力，结果显示，贴梗海棠与金钟花能适应高光，但光能利用率较低；木兰、日本樱花和紫荆对高光敏感，但适宜光强下光能利用率较高；龙爪槐对光能的适应和利用能力居中. 6个树种主要光合荧光参数与环境因子的相关分析表明，环境因子与光合荧光参数间存在相关关系，但不同物种间存在差异.     

热带雨林蒲桃属三个树种的幼苗由遮荫转入强光后叶片的光抑制

以热带雨林蒲桃属(Syzygium)不同演替阶段的3个树种思茅蒲桃(早期)、乌墨(中期)和阔叶蒲桃(后期)作为材料,通过测定在自然光和两种遮荫条件下(14％和42％自然光)的光合能力(Pmax)和色素含量,以及两种遮荫条件下3个树种移至全自然光下处理1d,研究它们叶片叶绿素荧光参数的日变化．结果表明,全光下思茅蒲桃和乌墨幼苗的P一比遮荫条件下的显著提高,阔叶蒲桃幼苗的光合能力却显著降低,并显著低于其它2个树种。全光下3个树种的Car含量和Car／Chl均高于生长在遮荫条件下同种植物,不同光强下阔叶蒲桃的Car／Chl高于乌墨和思茅蒲桃。一天中,全光下3个树种的凡一直上升,Fv／Fm下降,但在傍晚能够恢复到清晨的值,表明全光下3个树种通过PSI反应中心的可逆失活有效地防御了光破坏．而遮荫的3个树种转入全光后,Fo一直上升,Fv／Fm下降程度较大,在傍晚仍不能恢复,表明发生了光合机构的光破坏．虽然阔叶蒲桃的Car／Chl高于乌墨和思茅蒲桃,由遮荫转入强光后NPQ也上升较快,但其光合能力较低,一天中热耗散能力的增强仍不能有效消耗过剩的光能,导致对强光敏感,光抑制程度较乌墨和思茅蒲桃重,这与其耐荫性和演替状态是一致的。