光合作用和果树生产

高产果园群落应是适应栽培环境的高效光合系统,其最佳单位是有高光合能力的单株,叶只是其光合器官。叶的实际光合速率与8量子光合作用的理论光合速率相差甚远,这个差距是由于光合作用及其产物在运转和利用过程中的不利因素造成的。主要不利因素有1.LAI不足,对PAR的吸收不完全;2.光合产物在呼吸上的消耗;3.光合反应中心不足;4.电子传递系统和CO_2的吸收及传递系统的工作能力不足;5.水分、矿质营养的不平衡或温度不适。从光合生产的角度来看,高产果树栽培应有下列特点:1.叶对较大的PAR范围表现适应,光能利用率高,对水分和无机营养亏缺有较强的耐力;2.电子传递和还原能力强,向羧化中心扩散CO_2的阻力小,羧化活性高;3.在经常改变的外界条件下,能按植株需求改变光合速率和光合产物成分;4.有较高的经济系数;5.根系有较强的吸收力。因之,高产栽培的任务应是尽量减弱和消除不利因素的影响,把光合作用和生长发育协调起来,使果树遗传潜力得到充分发挥,以便創造出适应具体条件的高光合生产率果园群落。

PHOTOSYNTHESIS AND PRODUCTION OF FRUIT TREES

The culture community of a high-yield orchard should be ahighly efficient photosynthetic system adapted to its growingcircumstances. An optimal unit of this system had to be an individualtree with high photosynthetic efficiency, while a leaf was merely anorgan of this system. The actual photosynthetic rate of the leaf was farlower than that of the theoretical photosynthesis expending 8-quantaper CH_2O. This difference was caused by unfavorable factors inphotosynthesis, transport and utilization of its products. Theunfavorable factors were as follows: 1. insufficiency of LAI andincomplete absorption of PAR; 2. excessive consumption ofphotosynthate on respiration; 3. lack of photosynthetic reactioncenters; 4. lack of capacity in electron transferring system and insystem of absorbing and transferring CO_2; 5. imbalance of water andmineral nutrients and inadequate temperature. From point of view ofphotosynthetic production, high-yield culture should have the followingcharacters in common: 1 .The leaves were adapted to a larger rangeof PAR, the coefficient of light utilization was higher, the trees hadstronger resistance against water deficit and mineral nutrients deficit.2. The capacity of transferring electron and reduction was strong,the resistance of diffusing CO_2 to carboxyted center was small, the abilitly of carboxylation was high. 3. Under changeable environments,the photosynthetic rate and components of photosynthate could bechanged according to the requirements of the tree. 4. The economiccoefficient was higher. 5. The absorbing power of the root system wasstronger. High-yield culture, therefore, should weaken and clear upas much as possible effects of negative factors, harmonize photosynthesiswith the growth and development of the tree, and bring the geneticpotential of the trees into full play, so as to create orchard communityof highly photosynthetic productivity and suitable for concreteconditions.