Development of photosynthetic electron transport reactions under the influence of phytohormones and nitrate nutrition in greening cucumber cotyledons.

Development of the photosynthetic electron transport system, under the influence of hormones and nitrate-nutrition, in greening cucumber cotyledon was investigated. Both photosystems, PS I measured as DCPIP → MV, and PS II as H2O → pBQ, were significantly promoted by GA and kinetin with kinetin being more effective. PS II/PS I ratio, though increased in control, did not change significantly with GA or kinetin treatment. Other partial reactions (H2O → MV/K3Fe(CN)6/NADP) were also promoted. Addition of KNO3 showed concentration-dependent effects on growth and photosynthetic electron transport reactions (H2O → MV/K3Fe(CN)6/NADP). It is concluded that both hormones and nutritional status influence development of the photosynthetic electron transport system in greening cucumber cotyledons.