| Changes of the ecological factors in solar-greenhouse, and the growing and developing speed of cucumber leaves at different stages were studied. The characteristics of photosynthesis and photochemical efficiency throughout their ontogenetic periods, the characteristics of photosynthesis in different position leaves and the effect of plant density on photosynthesis, the solar energy utilization and the regulation of photosynthetic efficiency under low light density, the effect machenism of suboptimal temperature for long time and low temperature for short time under low light density on photosynthetic apparatus were also analyzed. The main results are as follows:　1. From November to next May, the photon flux density (PFD) in solar-greenhouse changed from 110 to 1068μmol·m-2·s-1 in sunny day. The air temperature (Ta) was 10～35℃ in daytime, and 8～27℃ in night. Soil temperature (Ts) was 12～28℃. Air relative humidity (RH) was 43～ 91% in general. The PFD, Ta, and Ts in solar-greenhouse were observed to be the lowest in Jan, second in Nov and Mar, and hightest in May. In sunny day, the PFD, Ta, Ts curves of diurnal variation showed single-peak which appeared at 12:00 a.m.～14:00 p.m.While the RH and CO2 concentration changed contrarily. The lowest Ta in night appeared at 4:00～6:00 a.m. The quantity of organic fertilizer had great influence on CO2 concentration in solar-greenhous. If sufficient organic fertilizer is applicated, the CO2 insolar-greenhouse could meet the demands of cucumber's growth.2. Leaves unfolded in Oct-Nov developed quickly, and had the largest leaf area. While those in Des-Feb developed slowly and the leaf area were the least. The photosynthetic rate(Pn) came to the largest on 20 days after leaves unfolded, and their increasing rate were greater than that of leaf area. During leaves coming out, stomatal and non-stomal factors existed simultaneously, and they all affected pn. The decline of photosynthetic founction maily depended on the non-stomatal limitation in the course of senescene. 3. The light saturation point and compensation point decreased as leaves unfolded. The apparent quantum yield (AQY), carboxylation efficiency (CE), and pigment content were　all samilar to Pn in changing trend. During early days of leaves unfolding, the photochemical efficiency increased as leaves grew. In the course of the senescene, the decreasing rate of Fv/Fm and фPSⅡ were less than that of Pn remarkably. The older the leaves, the larger light energy proportion were used for photochemical action, while the less for thermal energy dissipation. The process of CO2 assimilation was the primary determinant of photosynthetic ability throughout growth and development of cucumber leaves. 4.The Pn and CE of mid-position leaves were the highest. Low light density and CE were the major reasons for decreasement of Pn of lower-position leaves. The saturation light of the mid-position leaves were also the highest, while the photocompensation points of the upper, middle and lower position leaves decreased as leaf-position descended. The AQY, Maximal PSⅡ efficiency (Fv/Fm) and Actual photochemical efficiency of PSⅡ(ΦPSⅡ) of most leaves enhanced as leaf-positon descended.　 Pn curves of diurnal variation in different position leaves showed single-peak which appeared at 12:00 a.m., but the Fv/Fm and ΦPSⅡ changed contrarily,the variation extent mostly decreased as leaf position descended. The diurnal variation range of Fv/Fm and ΦPSⅡ in Jan. was less than that of in Nov.obviousy.The number of chloroplast, grana and lamella in lower position leaves were maximum, and their size of chloroplast were the largest. While those of 1st leaves were less. These indicated that unperfect chloroplast structure was one of the reasons for Pn decreased in upper positon leaves, and the lower position leaves had strong adaptive and regulative capicity to weak light envionment. The number of starch grain in 1st leaves were maximum, and those ofsize were the largest, while those of 4th leaves...
|
PDF Full Text Request