Quadratic relationship between the age of a tea leaf and the net photosynthetic rate (PN) has been found. A progressive increase in PN was recorded for four months. Then the PN slowly declined, yet even seven-month-old tea leaves sustained a low PN. In a tea shoot, the PN increased from the first leaf onwards. Besides the physiological maturity and proximity, photon flux density (PFD) played an important role in reducing the PN. The tea leaf PN was influenced by cultivation procedures which in turn disrupted the quantum of PFD transmitted through the canopy. and R. Raj Kumar, L. Manivel, S. Marimuthu.
Net photosynthetic rate (PN), transpiration rate (E), and stomatal conductance (gs) declined from upper leaves to the lower ones during dry and rainy seasons, indicating that long-term carbon budget should take into account PN variations for different leaf types. Relatively greater PN in the dry season suggested that this species is more able to maintain higher PN under drought, but the relatively higher E in the dry season might reduce water use efficiency (PN/E) for the species. Significant correlations between PN and gs indicated that gs may be the critical factor for PN variability in the desert region. and R. Z. Wang ... [et al.].