Photosynthetic responses of grafted bitter melon seedlings to flood stress

Young seedlings of bitter melon (Momordica charantia L. cv. New Known You #3) grafted onto luffa (Luffa cylindrica Roem. cv. cylinder #2) rootstocks were investigated for adaptation of photosynthetic activities under flooding conditions. Flooding treatment of grafted bitter melon seedlings reduced leaf photosynthetic rate, stomatal conductance, transpiration, soluble protein, and activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco) as compared with control seedlings. However, the effects were milder than those on ungrafted bitter melon. Furthermore, leaf internal CO2 concentration, per cent activation of rubisco, and starch content were similar in control and flooded seedlings, and no significant increase in leaf dark respiration rate was observed. Grafting of flood-intolerant bitter melon seedlings onto the flood-tolerant luffa rootstock improved flood tolerance.