桑树品种荷叶白的光合生理生态特性研究

荷叶白是生产上大面积栽植的桑树品种,研究了该品种2年生植株的光合生理生态特性,作为高产栽培技术的依据。该品种2年生植株的光饱和点和光补偿点分别为401、46.7μmol/(m2.s),表观量子效率为0.0598,暗呼吸速率为2.8μmol/(m2.s),最大净光合速率为21.2μmol/(m2.s),具有较低的光饱和点和补偿点,表现出较强的弱光利用能力;CO2补偿点为131.1μmol/mol,羧化效率为0.1472,光合能力最大值为84.6μmol/(m2.s),表现出较大光合作用潜力和生存能力;随着CO2浓度倍增,气孔导度、蒸腾速率均不同程度下降,而水分利用效率明显增强。采用逐步回归与通径系数分析表明,气孔导度、叶面饱和蒸气压亏缺及光合有效辐射是影响桑树叶片净光合速率变化最主要的直接作用因子。在生产上栽植桑品种荷叶白可采用宽行密株或宽窄行相间的密植栽培形式,提高单位面积产叶量,并可在坡度较大的背光地带栽植,以充分利用丘陵蚕区的阳光与地力。

An Investigation on Photosynthetic,Physiological and Ecological Characteristics of Morus multicaulis cv. Heyebai

In present study,photosynthetic,physiological and ecological characteristics of the broadly cultivated biennial Morus multicaulis cv.Heyebai were investigated as references for high yield cultivation technology.The results showed that light saturation point(LSP)and light compensation point(LCP)of the biennial plants was 401.0 and 46.7 μmol/(m2·s)respectively,apparent quantum yield (AQY) was 0.598,dark respiratory rate was 2.8μmol/(m2·s),and the maximun net photosynthetic rate (Pnmax)was 21.2μmol/(m2·s),all of which indicated high capability in utilizing weak light.The CO2 compensation point(CCP)was 131.1μmol/mol,the carboxylation efficiency(CE)was 0.1472,and the assimilation at saturating CO2(Pmax)was 84.6μmol/(m2·s),all of which showed high photosynthetic potential and vital capability.As CO2 concentration increased,the leaves'water utilization efficiency(WUE)was in-creased obviously while both stomatal conductance(Gs)and transpiration rate(Tr)declined in various degrees.Step-wise regression and path coefficient analysis indicated that stomatal conductance(Gs),vapor pressure deficit on leaf (VPD)and photosynthetically active radiation(PAR)were the most important direct factors that influenced Ret photosyn-thetic rate(Pn)of the leaves.The obtained results suggest dense planting forms with wide row space and narrow inter-plant space or with alternate wide and narrow row spaces for this mulberry cultivar so as to increase Iear yield per unit ar-ea.It can also be grown on apheliotropic slopes to fullyutilize the sunlight and land in hilly areas.