Physiological Responses of Apple Trees to Supraoptimal Root Temperature

Abstract

Ungrafted apple rootstocks were grown in sand cultures at constant root temperatures between 20°C to 40°C. Temperatures of 30°C and above reduced root and shoot growth. Serious damage to the leaves occurred at 35°C and above. The O2 consumption, CO2 evolution and respiratory quotient (RQ) of the roots showed maximum values at 35°C. Different rootstock cultivars varied greatly in their susceptibility to damage by supraoptimal root temperatures apparently due to anaerobic respiration. The more susceptible ones differed from resistant types in the larger amount of ethanol they accumulated in their roots at supraoptimal root temperature, and the more severe reduction in the malic acid content of the roots at such temperature. Acetaldehyde was also found in roots and leaves at supraoptimal root temperatures, whereas the organic acid content of the leaves tended to decrease. Supraoptimal root temperature also caused a reduction of cytokinins in both roots and leaves accompanied by a reduction in the leaf chlorophyll content. This could be prevented by the application of kinetin or benzyladenine to the leaves. In a short experiment a rise in root temperature up to 40°C caused an increase in transpiration and a decrease in the resistance of the leaves to the passage of water vapor, whereas in prolonged experiments transpiration reached a maximum and leaf resistance a minimum at 30°C. The leaf water potential increased also with increasing root temperature. Leaf temperature increased with increasing root temperature, irrespective of increasing or decreasing transpiration rates.

Effects of Soil Temperature on Growth and Root Function in Rice

“…), and apple trees (Malus sylvestris Mill. ), supraoptimal root temperature caused negative effects on shoot and root growth (Du and Tachibana, 1994a;Gur,et al, 1972;Lyons et al, 2007;Xu and Huang, 2000a), photosynthesis and carbohydrate metabolism (Du and Tachibana, 1994b;Xu and Huang, 2000b), and water and nutrient uptake (Huang and Xu, 2000;Klock et al, 1997;Tahir et al, 2008). The production of cytokinins and abscisic acid (ABA) in roots has been suggested to have a significant role in regulating shoot growth and photosynthesis under high soil temperature in wheat and grass (Liu and Huang, 2005).…”

Water relations, mineral nutrition, growth, and13C discrimination in two apple cultivars under daily episodes of high root-medium temperature

“…6). Gur et al (1972) reported that the optimum root-zone temperature for apple growth was between 18 and 25°C. Temperatures higher than 30°C were growth limiting.…”

Physiological Responses of Grain Legumes to Stress Environments

“…A 10 • C rise would have a proportionally even greater effect than the expected doubling of the temperature gradient. In addition to this direct effect of temperature on evaporation, it may further increase transpiration by maintaining the stomata open due to increased root temperature (Gur et al, 1972). The danger of drought injury under such conditions is obviously great, even without a deficiency in soil moisture.…”