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Cytokinins in Enhanced Growth and Tillering of Wheat Induced by Mixed Nitrogen Source
Author(s) -
Wang Xingting,
Below Frederick E.
Publication year - 1996
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/cropsci1996.0011183x003600010022x
Subject(s) - tiller (botany) , cytokinin , shoot , biology , exudate , agronomy , nitrogen , xylem , poaceae , horticulture , botany , chemistry , auxin , biochemistry , organic chemistry , gene
Supplying wheat plants with mixtures of NO 3 ‐ and NH 4 + increases growth and tiller production, but the physiological basis is unclear. Our objectives were to evaluate the roles for cytokinins and N use (e.g., accumulation, distribution, and utilization of absorbed N to produce tillers) in eliciting this response. Two species of spring wheat ( Triticum aestivum L. cv. Len and Triticum durum Desf. cv. Inbar) were grown hydroponically in the greenhouse with N supplied as all NO 3 ‐ , all NH 4 + , or an equal mixture of each form. In one experiment, the synthetic cytokinin N 6 ‐benzylaminopurine (100 µ M ) was applied repeatedly (a total of five times) to the shoots during tiller initiation and development, while in another, xylem exudate was collected from cut stumps during the early stages of tiller development. Plants not sprayed with cytokinins produced more tillers and accumulated more N when grown with mixed N than with either N form alone. Cytokinin sprays did not affect tillering of mixed N plants but increased tillers in all‐NO 3 ‐ grown or all‐NH 4 + ‐grown plants to levels close to that obtained with mixed N. For unsprayed plants, the presence of NH 4 + increased the shoot/root ratio, the proportion of N in the shoot, and the efficiency with which absorbed N was used to produce tillers, compared with plants grown with all NO 3 ‐ . Exogenous cytokinin appeared to mimic the effects of mixed N (and in some cases NH 4 + ) in altering the distribution and use of N by the plant. In addition, plants grown with mixed N or all NH 4 + exhibited higher concentrations and mass transfer of cytokinins in the xylem than those supplied with all NO 3 ‐ . These data are consistent with the interpretation that mixed N enhancement of tillering in wheat is due to increased synthesis of cytokinins, induced in part by use of NH 4 + ‐N.