Effect of benzylaminopurine on rehydration of bean plants after water stress

The possibility of improving the recovery of plant photosynthesis after wat er stress by cytokinin-induced stimulation of stomatal opening or delay of leaf senescence was tested. The 6-benzylaminopurine (BAP) in concentrations 1 and 10 muM was applied to the substrate (sand + nutrient solution) or sp rayed on primary leaves of 14-d-old Phaseolus vulgaris L. plants sufficient ly supplied with water or water-stressed for 4 d. The later ones having rel ative water content decreased to 69 % were fully rehydrated during the foll owing three days. Parameters of photosynthesis and water relations were mea sured in primary leaves of 7-, 10-, 14-, and 17-d-old plants. Application o f 1 CIM BAP slightly delayed leaf senescence: in 17-d-old control plants, n et photosynthetic rate (PN) and chlorophyll (Chl) content, and when sprayed on leaves also some of Chi a fluorescence kinetic parameters of BAP-treate d leaves were slightly higher than those of untreated leaves. Both types of application of 1 muM BAP slightly improved recovery of plants during rehyd ration after water stress in terms of increased gad, gab and PN, i.e., para meters which were markedly decreased by mild water stress. However, content s of Chi a, Chi b and carotenoids and parameters of Chi a fluorescence kine tic were not markedly affected by mild water stress and after rehydration w ere not stimulated by 1 muM BAP. 10 muM BAP had mostly negative effects on the parameters measured.