Total chlorophyll content
Plants grown in 0.5 mM nitrate had more chlorophyll content followed by plants grown in
0.1 mM, 0.05 mM and control as shown in Figure 8. Up to 30 days the chlorophyll content
increased in all the four treatments and there after it decreased gradually i.e. the chlorophyll content
was more during the vegetative periods and then became almost stagnant on approach of
reproductive cycle. This suggested that synthesis of chlorophyll took place up to 30 days and maximum
content was found during mid vegetative periods. After this time interval of active synthesis,
may be the rate of synthesis of chlorophyll attained a steady state and a constant level was maintained
in leaf till it reached the reproductive stages. This may enable the plant to carry out maximum
photosynthesis and accumulate energy in the form of carbohydrates which may be utilized
bythe plant for its further growth and development. Compared to control plants, 0.5 mM plants
had more than 2 times chlorophyll content. Plants grown in 0.1 mM and 0.05 mM nitrate also had
more chlorophyll content than control plants. This suggests that nitrogen plays a role in maintenance
of chlorophyll content of leaves in plants. Leaf photosynthesis increases together with leaf N
content and a significant effect of leaf N content on light use efficiency has been reported (Grindlay,
1997). It has been concluded that the impact of N supply on leaf growth was mostly due to
increased cell growth rate with larger cell size (Gastal and Lemaire, 2000).