辣椒幼苗叶片解剖特征及光合特性对弱光的响应

Response of Anatomical Structure and Photosynthetic Characteristics to Low Light in Leaves of Capsicum Seedlings

以4个弱光适应性不同的辣椒(Capsicum annuum L.)基因型(甜味型和辣味型)为试材,在人工气候室内研究了弱光(75～100μmol.m-2.s-1)条件下幼苗叶片显微结构、叶绿体超微结构、气孔特征,以及光合特性的适应性变化。结果表明,弱光下辣椒幼苗叶片变薄,栅栏组织/海绵组织比值增加,‘伏地尖’(辣味型)和‘上海圆椒’(甜味型)具有较高的栅栏组织/海绵组织比值;叶绿体数减少,但叶绿体变大,基粒数、基粒厚度和基粒片层增加,淀粉粒增大、增多,2个辣味型材料比2个甜味型材料具有较高的叶绿体数和基粒数。辣椒(甜味型)展叶过程中下表皮气孔密度下降,而展叶14d以后的气孔指数和单片叶气孔数变化不大。弱光下叶片气孔密度、气孔指数和单片叶气孔数减小,但气孔变大,其中‘上海圆椒’气孔纵轴、横轴较正常光照下增加,‘20078’则横轴显著增加;弱光环境中叶片表皮细胞变大并发生扭曲皱褶,气孔与表皮平齐或略显外突,保卫细胞角质层上可观察到明显的环状褶皱。弱光下辣椒幼苗的光饱和CO2同化速率(Asat)、暗呼吸速率(Rd)、夜间呼吸速率(Rn)、光呼吸速率(Rp)、光补偿点(LCP)、光饱和点(LSP)、CO2补偿点(Г)、CO2饱和点(CSP)、羧化效率(CE)以及RuBP最大再生速率下降,表观量子效率(Фi)上升;辣味型较甜味型材料Asat下降幅度较小,并且具有较低的LCP、LSP及其Rd、Rn和Rp。弱光下各基因型辣椒的光合启动时间均有所延长,弱光敏感性材料表现更为明显。

Four genotypes of capsicum （ Capsicum annuum L. ） with distinct low light tolerance were used to study the response of anatomical structure, ultrastructure of chloroplast, stomatal characteristics and photosynthetic characteristics of leaves to low light （75 - 100 μmol.m^-2.s^-1） in a phytotron. The results revealed that leaves treated with low-light became thinner with an increase of palisade/spongy tissue ratio, and two genotypes including hot pepper ＇ Fudijian＇ and sweet pepper ＇Shanghai Yuanjiao＇ had higher ratio than the other two. Under low light, the number of chloroplast decreased, but the size of chloroplasts and starch grains, the number of grana, grana lamella, starch grain and grana thickness of chloroplast increased. Comparing with sweet pepper, hot pepper had more chloroplasts and granas. In sweet pepper, the stomatal density in lower epidermal descended during leaf unfolding, but no more changes of stomatal index and number of stomata per leaf occurred after 14 days of leaf unfolding. Low light treatment resulted in decreases of stomatal density, stomatal index and number of stomata per leaf, and increases of the stomatal size, the vertical and horizontal axes of stomata in ＇ Shanghai Yuanjiao＇. Simultaneously, the longer horizontal axes of stomata were also observed in another genotype ＇ 20078＇. The epidermal cells of sweet pepper grown under low light were large and distorted. Meanwhile the stomata and lower epidermal cell were equal height or the stomata slightly protruded out of the epidermal wall. The cycle wrinkle could be obviously observed on cuticle of guard cell in lower epidermis of leaves under low light. Photosynthetic parameters including light saturated rate of the CO2 assimilation （ Asat, ）, dark respiration rate （ Rd ）, night respiration rate （ Rn） , light respiration rate （ Rp ）, light compensation point （LCP）, light saturation point （LSP）, CO2 compensation point （F）, CO2 saturation point （CSP）, carboxylation efficiency （CE） and maximum RuBP regeneration rate decreased, while apparent quantum yield （Фi） increased under low light. The Asat decreasing, LCP, LSP, Rd, Rn and Rp were lower in hot pepper than those in sweet pepper. The start time of photosynthesis （ namely, the net photosynthetic rate i. e. P, from zero to maximum） in low-light leaves was relatively prolonged, especially in low light-sensitive than in low light-tolerant genotypes. Hence, some adaptive response of photosynthetic characteristic to low light have happened in capsicum leaves.