Additionally, the levels of chlorophyll and fluoresces of the leaf determined (Minolta SPAD and chlorophyll fluorometer -opti-sciences OS-30p UK) while the leaf photosynthetic rate (pn), stomatal conductance (gs) and internal concentration of CO2(Ci) determined using a portable infra-red gas analyser (model Li-6200,Li-Cor,Inc.,Lincoln,Nebr)