The level of chlorophyll in the youngest expanded leaves and old leaves was recorded by taking SPAD (chlorophyll content)readings with a SPAD-502 Chlorophyll Meter (Minolta Camera Co.Ltd., Japan). Chlorophyll a, chlorophyll b and carotenoids were extracted from leaf tissue with methanol and estimated according to Lichtenthaler and Wellburn (1983). Second leaves from top(young leaves) and bottom (old leaves) were used for the measurement of chlorophyll fluorescence using a Plant Efficiency Analyzer,Handy PEA (Hansatech Instruments Ltd., Norfolk, UK). Leaves were maintained in darkness for 15 min before taking the data on chlorophyll fluorescence. Maximal quantum yield of PS II photochemistry(Fv/Fm) were calculated using the software supplied by the manufacturer.