Abstract

The effects of different temperature regimes of hydroponic solution on the chlorophyll pigmentation and photosynthesis of Ornithogalum longibracteatum L. were determined in the glasshouse for 10 weeks in 2009 and 2010. The plants were irrigated with hydroponic solution, heated to various temperatures (26, 30 and 34°C) via pumps connected to 4 sets of water tanks, each maintained at the experimental temperatures using dolphin aquarium heaters. Unheated water supplied from the fourth tank served as control (temperature ranged between 10 and 15°C (day/night) throughout the experiment period). All plants were supplied with 1 mgL^-1 nutrient solution of (hortical) and the solution was changed at weekly intervals. After 2 to 10 weeks of experimentation, data showed that chlorophyll a, b and total, were significantly increased by elevating hydroponic solution temperature from 26 to 30°C, and started decreasing at 34°C compared with the control in both 2009 and 2010. Photosynthesis rate (A) and the gas exchange parameters; stomata conductance (gs), intercellular CO₂ concentration (Ci) and transpiration (E), were significantly increased by elevating the hydroponic solution temperatures from 26 to 30°C compared with the control, and then decreased significantly at 34°C. The findings from this study suggest that the performance of O. longibracteatum can be improved during winter seasons by heating the hydroponic solution up to 30°C. Beyond this, temperature led to impaired chlorophyll formation and reduced photosynthesis.

Key words: Intercellular CO₂ concentration, photosynthesis rate, stomata conductance, transpiration.