Effects of different intensities of red or blue on chlorophyll fluorescence characteristics of bean leaves

Common bean is widely planted all over the world with a wide variety of ecological conditions. The photosynthesis of bean leaves varies remarkably under different ecological conditions which may be correlated to differing light quality and the light intensity. In order to study the effects of different intensities and qualities of the light on the photosynthesis of plant,bean( Phaseolus vulgaris) leaves were used as the material,and Pulse-Amplitude-Modulation chlorophyll fluorometer was used to record the changes of the chlorophyll fluorescence parameters with different light intensities of red or blue,primary leaves were offered to the treatments in the present work. The results showed that the maximum photochemical efficiency of light adaptation( Fv' / Fm',the efficiency of capture excitation energy in PSⅡ reaction center)decreased with the increase of light intensities of red or blue light,but the values of Fv' / Fm' under blue light were significantly( P 0. 05) or very significantly( P 0. 01) higher than those under the same intensities of red light. With the increase of light intensities of blue light,the actual photochemical efficiency of PSⅡ( Y(Ⅱ),the actual photochemical efficiency of PSⅡ under light) and the coefficient of photochemical fluorescence quenching( q P and q L,the proportion of reduction state of PSⅡ original electron acceptor-plastoquinone( QA) increased but became stable gradually,while the values of Y(Ⅱ),q P and q L decreased with the increase of red light intensities. These meant that the photosynthetic efficiency of bean leaves decreased with the increase of blue or red light intensities. Non-photochemical quenching coefficient( NPQ,the excess energy dissipation by PSⅡ antenna system),electronic transmission rate( ETR,ETR increases linearly with light intensity,until it reaches a maximum. This happens when the capacity of all electron sink is reached),and quantum yield of regulated energy dissipation[Y( NPQ),an important indicator of self protection and the ability of PS Ⅱto deal with excess light energy]increased with the increase of blue light or red light intensity. Compared to under red light,the values of ETR under blue light were higher but the values of NPQ and Y( NPQ) were lower. Quantum yield of non-regulated energy dissipation[Y( NO),the proportion of excess light energy in the form of heat and fluorescence,one of the important indicators of light damage]increased with the increase of red light intensity but decreased with the increase of blue light intensity. These results showed that the photosynthetic efficiency of bean leaves decreased with the increase of light intensities,but the absorbing and utilizing efficiencies of blue light were higher than those of red lights.We believe that this work would be helpful in developing current understanding on the responses of plants to different light intensities and qualities.