Growth and photosynthesis of Gossypium hirsutum L at high photon flux densities: effects of soil temperatures and nocturnal air temperatures

Abstract

Gossypium hirsutum, when grown under both medium (1 000-1 100 μmol m-2 s-1) and high photon flux densities (PFD, 1800-2000 μmol m-2 s-1) showed reduced total dry weights and total leaf areas with decreasing temperatures during the dark period (25, 15 or 10 °C), while photosynthetic capacity (PSmax) and quantum yield of photosynthetic O2 evolution (Ø), as well as the light-use efficiency of photosystem II ( FV FM) were not affected. Maintaining a day/night soil temperature of 25 °C for one set of plants (high PFD, 34 °/10 °C) resulted in a 44% increase in total dry weight, an increase in turgor pressure, but no significant change in PSmax. During another set of experiments cotton plants were cultivated at either medium PFD and 20 25 °C (day / night) air temperatures or at high PFD and either 24 25 °C or 34 25 °C air temperatures. The soil temperatures were maintained independent of the air temperatures at either 20° or 30 °C. Cultivating the plants at a soil temperature of 30° rather than 20 °C resulted in large percentage increases in total dry weight (28-55%), but did not have any impact on FV FM and the pigment content of the leaves. The importance of night and rhizosphere temperatures for plant growth and development are discussed. © 1993.