Premium
Osmotic Potential and Starch Accumulation in Leaves of Field‐Grown Soybean 1
Author(s) -
Cortes P. M.,
Sinclair T. R.
Publication year - 1987
Publication title -
crop science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.76
H-Index - 147
eISSN - 1435-0653
pISSN - 0011-183X
DOI - 10.2135/cropsci1987.0011183x002700010021x
Subject(s) - starch , osmotic pressure , biology , shading , botany , loam , volume (thermodynamics) , horticulture , food science , soil water , ecology , art , visual arts , physics , quantum mechanics
Although osmotic adjustment in response to a variety of factors has been observed in the leaves of numerous species, the mechanism by which it occurs is still unclear. It has been suggested that, in some cases, enlarging starch granules within leaf cells displace part of the symplasm and result in osmotic adjustment of the remaining osmotic volume. This study tested whether such a mechanism operated in the leaves of field‐grown soybean [ Glycine max (L.) Merr.]. Plants of the cv. UFV‐1 were grown in the field on Arredondo fine sand (loamy, siliceous, hyperthermic Grossarenic Paleudult) and their uppermost, fully expanded leaves were sampled at dawn during midpodfill. In order to vary the amount of leaf starch, the plants were subjected to four treatments; (i) no shading, (ii) intermittent shade without pods, (iii) intermittent shade with pods, and (iv) continuous shading. Leaf osmotic potential was measured with a thermocouple psychrometer and starch concentration was determined for the same leaves by first hydrolyzing the starch and then measuring the resulting glucose. Naturally occurring light fluctuations were found to result in predawn osmotic adjustment, and increases in incident radiation resulted in an increase in starch and an associated decrease in osmotic potential. The changes in osmotic potential could only be partially explained as the result of a physical system in which the volume of starch varied and changed the osmotic volume.