Possible effects of regulating hydroponic water temperature on plant growth, accumulation of nutrients and other metabolites

Water temperature can affect many physiological processes during plant growth and development. Temperatures below or above optimum levels may influence plant metabolic activities positively or negatively. This may include accumulation of different metabolites such as phenolic compounds, reactive oxygen species (ROS), nutrient uptake, chlorophyll pigment formation, the photosynthesis process and finally the growth and development of the plant. The optimum temperature of the growthmedium can contribute to improving and optimising the earlier mentioned plant physiological processes. Information on how the temperature of hydroponic solution influences certain flowering plant production in glasshouses during the winter period is limited. This review suggests the possible benefits of regulating temperatures of the hydroponic solution with the aim of optimising production of flower in the glasshouse during winter periods.Keywords: Chlorophyll, nutrient uptake, phenolic compounds, photosynthesis rate, reactive oxygen specie

Chlorophyll pigmentation and photosynthetic parameters in Ornithogalum longibracteatum L. as affected by varying temperatures in hydroponics solution

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.Cape Peninsula University of Technology through University Research Fund (RP 03

Effect of regulated irrigation water temperature on hydroponics production of spinach (Spinacia oleracea L.)

The effects of different temperature regimes of irrigation water on the growth rate of Spinacia oleracea L. were determined in the greenhouse for 8 weeks. Thespinach seedlings were irrigated with water heated to various temperatures (24, 26 and 28°C) via pumps connected to 4 sets of water tanks each maintained at the experimental temperatures using Dolphin aquarium heaters. Unheated water from the tap supplied from the fourth tank served as control. All the plants were supplied with a mixture of Ocean HYDROGRO and Ocean HORTICAL nutrient solutions containing all essential elements. After 8 weeks of growth, results showed that leaf length (mm), leaf number and total fresh and dry weights (g per plant) was higher in plants grown at elevated temperatures compared with the control plants with optimum growth being recorded at 28°C. These results suggest that controlled production of spinach during winter seasons is possible by irrigation with heated water in a greenhouse

Closed hydroponic systems : operational parameters, root exudates occurrence and related water treatment

Greenhouse production of vegetables in closed hydroponic cropping systems is a resource-efficient technique for the production of high-quality produce with a high yield per unit area. Recently, there have been considerable progresses in the development of hydroponic culture. While this type of cropping system allows savings in terms of water and nutrient use, the recirculation of water increases the risk of root exudates dispersal. Plant roots often exude numerous organic acids, which are known to inhibit growth. So far several methods have been found to be effective in removing or degrading the phytotoxic substances released from plant roots during autotoxicity such as adsorption by activated carbon, electrodegradation of root exudates and TiO2 photocatalysis. In this review an overview will be presented of hydroponic systems and their related root exudates occurrence and removal