Photosynthetic Activities and Growth Rate of Cowpea (Vigna Unguiculata L. Walp) Inoculated with Rhizobia at Two Developmental Stages.

Abstract

This study investigated the effect of symbiotic N-source on the photosynthetic activities of cowpea at different developmental stages. Treatments were two developmental stages (vegetative and reproductive) and five N-sources (control, inoculation with BR 3267, BR 3262, USDA 3451 rhizobia strains and 90kg N ha-1 application). Chlorophyll fluorescence parameters and crop growth rate were measured. All the treatments had significantly higher quantum yield of photosystem II at their vegetative stage than reproductive stage (P<0.05) except plants to which 90kg N ha-1 was applied which maintained similar values at both stages. Opposite trend was observed for quantum yield of non-photochemical quenching. Plants which received 90kg N ha-1 had significantly higher growth rate at the reproductive stage than others which had statistically similar growth rates. It can therefore be concluded that application of nitrogenous fertilizer sustained significantly high quantum yield of photosynthesis and dry matter production in cowpea at reproductive stage.