Effect of different container sizes and irrigation frequency on the growth and gas exchange characteristics of mango (Mangifera indica L.) rootstock seedlings

Studies were conducted from July 2003 to March 2005 in a polythene-covered greenhouse at Maseno University, Kenya, to investigate the effect on morphological and physiological parameters of mango (Mangifera indica) rootstock seedlings of three container sizes: V₁ (1.7 l), V₂ (2.7 l), V₃ (3.9 l), and three irrigation frequency levels W₁ (irrigating every day), W₂ (irrigating every two days), W₃ (irrigating every three days). The experimental design was a completely randomized design. The morphological parameters determined were number of leaves, plant height, stem diameter, shoot and root dry weights, whole plant dry weight and root to shoot ratio. The physiological parameters were CO₂ assimilation rate, substomatal CO₂ concentration, transpiration rate, stomatal conductance and soil respiration. The results showed that container size significantly (P=0.05) increased plant height, canopy height, shoot and root dry weight, whole plant dry weight, root to shoot ratio and number of leaves. Irrigation frequency significantly increased the number of leaves, plant height, roots and shoot dry weight, root to shoot ratio, and whole plant dry weight, but did not affect canopy height or stem diameter. The interaction between irrigation frequency and container size had no effect on canopy height and whole plant dry weight but increased all the other determined parameters. Container size and irrigation frequency did not affect substomatal CO₂ concentration but significantly increased soil respiration and CO₂ assimilation rate during the early months of growth. The interaction between container size and irrigation frequency was significant for CO₂ assimilation rate, transpiration rate, soil respiration and stomatal conductance. It is concluded that container size and irrigation affect plant growth through morphological and physiological changes in mango rootstock seedlings.