Leaf Anatomy and Water Relations of Plants Grown in Controlled Environments and in the Field1

Abstract

Structure and physiology of plants grown in controlled environments and in the field are compared. Cotton (Gossypium hirsutum ‘McNair 511’) and soybean (Glycine max ‘Ransom’) plants were grown from seed in 1:1 vermiculite and gravel mixture contained in 25‐cm plastic pots in the field, in an air‐conditioned greenhouse at 30 C/26 C, and in growth chambers at 30 C/26 C and 28 C/17 C day and night temperatures. In both species, leaves of field grown plants were considerably thicker than leaves of plants grown in chambers at 30 C/26 C. (field soybeans, 119 µ; chamber soybeans, 58 µ, field cotton, 139 µ; chamber cotton, 101 µ). Leaves of both species were as thick when grown in chambers with a 28 C/17 C regime as when grown outdoors. Stomatal frequency was 2 to 5 times greater on the lower than on the upper sur. face of cotton leaves and 3.5 to 8 times greater on the lower than on the upper surface of soybean leaves. The ratio of lower stomata to upper stomata in cotton leaves varied from environment to environment as follows: field > greenhouse > 30 C/26 C chamber > 28 C/17 C chamber, but for soybean the order was field > 28 C/17 C chamber > greenhouse > 30 C/26 C chamber. The environment had little effect on stomatal size in cotton, but upper stomata of field‐grown soybeans were larger (18.7 µ) than those of chamber‐grown plants (12.0 µ). Transpiration resistance was greater for the upper surfaces of leaves of both species grown in all environments (soybeans 1.2 to 4.2 s cm‐1, cotton 1.0 to 8.2 s cm‐1). In both species a waxy bloom was evident on the lower surface of leaves of field‐grown plants and not on the lower leaf surface of greenhouse or warm chamber plants. Soybeans grown in the 28 C/17 C chambers had more lower surface bloom than soybeans grown in warm chambers. In general, soybean leaf development was more sensitive to the environment than cotton leaf development.