Growth and Photosynthesis of Pummelo Leaf cv. Kao-thongdee (Citrus maxima (Burm.) Merr.)

Abstract

Leaf growth and photosynthesis of pummel (Citrus maxima) cultivar Kaothongdee were studied in nursery of the Scientific and Technological Equipments, Walailak University, Thasala district, Nakhon Si Thammarat province during May, 2008 to October, 2009. The objectives were to investigate leaf growth pattern and net photosynthesis rate of pummel leaf. Leaf growth of pummelo was found to be divided into three periods. The first period was from bud burst to 2 days after emergence, leaf width and leaf length increased slowly. The second period form 2-10 days after emergence, the leaf growth increased rapidly. The third period form 22-28 days after emergence, the leaf growth increased slowly and reached the maximum on 28 days after emergence. Total chlorophyll concentrations in leaf at different ages increased gradually and reached the maximum 2 months after emergence (45.09 micromol) and declining at the beginning of the 5th month after emergence. The nitrogen concentrations in leaf at different ages gradually increased and reached the maximum 4 months after emergence (2.22 % dry weight) and declining at the beginning of the 6th month after emergence. While photosynthetic rates of leaves rapidly increased and reached the maximum 2 months after emergence (12.8 micromol CO2/m2/s) and then began to gradually decline at the beginning of the 5th month after emergence. Net photosynthetic rates of leaves in diurnal rapidly increased and reached the maximum 9.00-10.00 O’clock (4.62 micromol CO2/m2/s) and then began to gradually decline.