Abstract
Eight plots of different temperature combinations of air and soil were established to compare the responses in growth and chemical constituent both in orchardgrass and perennial ryegrass plants, grown in 4 phytotrons with different air-temperatures from 90 to 28°all dry under natural day light. 1. In both grasses, the growth in terms of plant height, leaf-emergence rate, heading date, tiller number, leaf area and dry matter production was promoted by raising or lowering several degrees of soil-temperature when the air-temperature was lower or higher than the optimum, respectively. The production of dry matter was highest in air 17°-soil 23°plot, followed by 23-17°, 23-23°and 17-17°. 2. Generally, nitrogen concentration of each organ was higher under cooler air-temperatures, although a little higher under 28°. With the growth promotion by the soil-temperature alteration, both nitrogen concentration and Sol-N/Tot-N ratio declined. TAC concentration increased with the increase of air-temperature in orchardgrass, whereas decreased in perennial ryegrass. The concentration was generally higher under the soil-temperatures whereby the growth was promoted. Therefore, Tot-N/TAC ratio was greater under cooler air-temperatures in orchardgrass but smaller in perennial ryegrass, and in both grasses declined with the greater growth rate induced by the alteration of soil-temperature. 4. Both crude protein and TAC production were less under 9°and 28°, higher under 17°and 23°air-temperatures, respectively, being highest under 17-23°and 23-17°conditions. In the regime of this experiment, it is suggested that the production of protein and TAC increase in parallel with that of dry matter.
