Characteristics of photosynthesis machinism in different peach species under low light intensity

Chino. 探讨弱光条件下设施桃树叶片光合器官结构特征变化及品种间差异，为设施桃品质改良提供理论依据。以设施栽培的庆丰和麦香桃树为试材，设置全光照(CK)、60%～70%光照(T1)和30%～40%光照(T2)3种处理，测定了弱光条件下桃树功能叶片净光合速率(Pn)，观察了气孔形态；分析了桃树新梢的不同部位叶片的叶绿素含量（chl）、叶片结构特征；采用透射电镜观察了弱光条件下桃树新梢不同部位叶片的叶绿体超微结构；比较了品种间差异。随着光照强度的减弱，桃叶片Pn 降低；而T1提高了麦香叶片10：00和14：00的Pn；叶片气孔密度、气孔开张度和气孔导度(Cs)下降；叶片Chl总量、Chl a、Chl b的含量显著增加。叶片的叶面积、叶比重、上下表皮厚度、海绵组织厚度降低，而栅栏组织厚度和栅/海比升高；叶肉细胞内的叶绿体数增多，叶绿体基粒明显变厚，基粒数和基粒片层数增加，新梢上位叶片栅栏组织叶绿体内的淀粉粒数降低，下位叶片栅栏组织的淀粉粒数增加。弱光条件下新梢不同部位叶片间和不同品种间的叶片Chl、Pn、气孔行为、叶片结构特征、叶绿体结构特征表现显著差异。

Inglés. The objective of this paper was to investigate the effect of weak light intensity on the leaf structure of various peach varieties under the solar greenhouse and to find the different response mechanism between them. Qingfeng and Maixiang were growing under the solar greenhouse, the low light was simulated with shade film to the three degree of 100% light intensity(CK), 60%-70% light intensity(T1) and 30%-40% light intensity(T2). The net photosynthesis rate was measured, and the stoma morphic difference was observed, at the same time the chlorophyll content and leaf structure were analyzed.The chloroplast micro-ultrastructure of peach leaf under solar greenhouse were observed under microscope, and the effect of low light on the peach tree was compared. The results showed that as the light intensity was lower, the net photosynthesis rate (Pn) decreased, whereas the net photosynthesis rate of Maixiang increased at 10:00 o’clock and 14 o’clock respectively. The stoma density, stoma aperture and stoma conduct(Cs) were lower than that under normal light intensity; The total chlorophyll content (Chl(a+b)), chlorophyll a (Chl a) and b (Chl b) content increased, while the ratio of Chl a to Chl b decreased. With the shade degree aggravated, the leaf area, the ratio of leaf area to leaf weight, and the thickness of leaf up and low epidermis declined, it is the same for the thickness of sponge tissue. The ration of the palisesade tissue thickness to the sponge tissue enhanced. Growing under low light, the chloroplast number ascended, the grana lamella was thicker and the grana number was more than that under normal light intensity. The amyloid number per chloroplast in palisesade tissue of upper leaves declined, that was reversed of lower leaf. All the data indicated that there were distinctive differences between the peach species in the Chl content, Pn, stoma characteristics, leaf structure, and the chloroplast structure.