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Water Status of the Developing Grain of Maize 1
Author(s) -
Westgate mark E.,
Boyer John S.
Publication year - 1986
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj1986.00021962007800040031x
Subject(s) - anthesis , turgor pressure , agronomy , water content , dry matter , maturity (psychological) , osmotic pressure , chemistry , hybrid , horticulture , biology , cultivar , psychology , developmental psychology , geotechnical engineering , engineering , biochemistry
Developing grain undergoes large changes in water content. Since there are no direct vascular connections between the grain and the maternal plant, grain growth may depend on large osmotic forces. To determine the nature and magnitude of these forces, we investigated the water potential ( Ψ w ), osmotic potential ( Ψ s ) and turgor in the developing grain of maize ( Zea mays L.) from anthesis to harvest maturity in three commercial hybrids grown in the field. Grain Ψ w , Ψ s and turgor were determined using isopiestic thermocouple phychrometry. Seasonal trends in grain Ψ w were similar in all three hybrids despite differences in maturity rating (85 to 110 days), maximum grain water content, and environmental conditions after anthesis. Prior to maximum dry matter accumulation (physiological maturity), grain Ψ w was 0.4 to 0.9 MPa lower than leaf Ψ w reasonably stable, and largely independent of atmospheric conditions. Variations in grain Ψ w were similar to the changes in grain Ψ s which was between −0.7 and −1.6 MPa and not affected by matric forces. Turgor was usually 0.2 to 0.3 MPa. After maximum dry matter accumulation, grain Ψ w responded to atmospheric conditions and decreased rapidly to potentials as low as −8.5 MPa as grain water content decreased and large matric forces developed. The relationship between grain Ψ w and percent grain moisture (PM) was similar for all three hybrids and given by PM = 23.7 Ψ w −1.16 + 20 ( r 2 = 0.83). These results indicate either that a large hydraulic resistance exists or that high solute concentrations are present between the developing grain and the vascular supply of the maternal plant. Thus, large osmotic forces are associated with water uptake by the grain. Also, prior to physiological maturity, grain Ψ w is controlled mostly by the internal metabolic events associated with development. After physiological maturity, however, it is controlled mostly by grain moisture content.