Substrate pH and Papaya Seedling Growth

Abstract

Two studies were conducted to determine the influence of pH on `Waimanalo' papaya seedling growth and morphology. The seedlings were grown in clear, plastic tubes with diameter of 7 cm and length of 21 cm, and substrate was silica sand. The substrate was drenched daily with complete nutrient solution. The solution was adjusted to pH of 3, 4, 5, 6, 7, 8, or 9. We used direct-seeded plants in the first study, and plants were harvested following 9.5 weeks of growth. We used transplants in the second study, and plants were harvested following 4 weeks of growth. Dry mass of plants was relatively unaffected by substrate pH within the range of 4 to 9. In both studies; however, dry mass of plants receiving solution with a pH of 3 was reduced. The response pattern was similar for canopy:root ratio, total root length, root growth rate, lateral root thickness, and root tip density. Unit leaf area per unit root length was greatly increased for plants receiving pH of 3, indicating increased susceptibility to drought conditions.