水深对苦草生长及叶片PS Ⅱ光化学特性的影响

Effects of water depth on the growth of Vallisneria natans and photosynthetic systemⅡ photochemical characteristics of the leaves

利用植物效率仪(Handy-PEA)测定水深0.6、1.3、2.0 m下苦草叶片的快速荧光诱导动力学曲线(OJIP曲线),并采用JIP-test方法分析和处理数据,研究水深对苦草生长和叶片光合机理的影响.结果表明:随着水深增加,水下光强显著衰减,苦草生物量、无性系分株数、叶片数、根系总长度、根系表面积等形态指标显著降低,而最大叶长、平均叶长、最大叶宽无显著变化,2.0 m水深对苦草的生长产生了负面影响;单位反应中心吸收、捕获、电子传递、传递到电子传递末端的量子效率(ABS/RC、TR0/RC、ET0/RC、RE0/RC)显著降低,单位反应中心的耗散量子效率(DI0/RC)也显著下降,导致3种水深处理下单位反应中心吸收的能传递电子链末端的效率(φR0)以及用于电子传递的能量成功传递到电子链末端的效率(δR0)差异不显著,表明水深梯度对单位反应中心光合效率影响不显著;单位面积反应中心数(RC/CS0)显著增加,相同受光面积时水深2.0 m处叶片光合作用显著强于水深0.6 m处;性能参数PIabs、PIcs和PIabs,total显著提高,表明低光胁迫有利于光能向活跃化学能转变.苦草叶片通过激活未激活的反应中心,而不是提高单位反应中心光能利用效率来适应弱光强,且水深1.3 m较适合苦草生长.

The effects of water depth on the growth of Vallisneria Ⅱ photochemical characteristics of the leaves were investigated natans and photosynthetic system at three depths of 0.6, 1.3 and 2.0 m. The rapid fluorescence induction kinetics curves （OJIP） of the leaves were measured with Plant Efficiency Analyzer and analyzed with JIP-test. The results indicated that the light intensities at water depths of 0.6, 1.3 and 2.0 m were obviously different and the growth of V. natans was re- stricted under water depth of 2.0 m. Biomass, number of ramets, number of leaves, total root length, root surface area and other morphological indices decreased significantly with the increasing water depth, and the maximum leaf length, average leaf length, maximum leaf width changed insig- nificantly with the water depth. With the increasing water depth, absorption flux per reaction center （ABS/RC）, trapped energy flux per RC （TR0/RC）, electron transport flux per RC （ETo/RC）, reduction of end acceptors at photosynthetic system Ⅰ（ PSⅠ ） electron acceptor side per RC （RE0/ RC） decreased significantly. The dissipated energy flux per RC （DI0/RC） also decreased signifi- cantly, which led to no obvious difference in quantum yield for the reduction of end acceptors of PS I per photon absorbed （φR0） and the efficiency for the trapped exciton to move an electron into the electron transport chain from QA- to the PS I end electron acceptors （δR0）. Because the amount of active PS Ⅱ RCs per CS increased significantly, photosynthesis per area of V. natans grown at 2.0 m was significantly greater than that of V. natans grown at 0.6 m. The performance index Plabs, Pies, P/ass.total photochemistry efficiency of leaves of V. natans grown at 2.0 m was significantly in-creased, suggesting that hght stress may promote a more efficient conversion of light energy to active chemical energy. V. natans leaves accommodate the low light intensity environment through activa- ting inactive reaction centers but not through improving light utilization efficiency per reaction cen- ter, and the water depth of 1.3 m may be more suitable for the growth of V. natans.