Growth responses of seminal roots of wheat seedlings to a reduction in the water potential of vermiculite |
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Authors: | Mohammad Akmal Tadashi Hirasawa |
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Institution: | (1) Faculty of Agriculture, Tokyo University of Agriculture and Technology, Fuchu, Tokyo 183-8509, Japan;(2) Department of Agronomy, NWFP Agricultural University, Peshawar, Pakistan |
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Abstract: | We examined the elongation rate, water status and solute accumulation in the seminal roots of wheat seedlings (Triticum aestivum L.) that were growing in vermiculite with a water potential (Ψw) ranging from −0 03 to −1 10 MPa. The elongation rate of the primary seminal root was similar to that of the first pair of
seminal roots but that of the second pair of seminal roots was lower at all values of Ψw tested. The elongation rate was highest in vermiculite with a Ψw of −0.03 MPa but did not decrease significantly until the Ψw was reduced to −0.15 MPa. Further reductions in Ψw reduced the elongation rate markedly. The Ψw of mature tissues was always similar to that of vermiculite. The osmotic potential (Ψo) decreased to the same extent as the decrease in Ψw. Thus, the turgor pressure (Ψp) remained unchanged even in vermiculite with a low Ψw. In elongating tissues, Ψw and Ψo were far lower than they were in mature tissues and, thus, reductions in turgor were not significant. Even when the Ψw of vermiculite changed, there were no consistent changes in terms of a difference in Ψw between elongating plus mature tissues and vermiculite. There were also no consistent changes in levels of osmotica, calculated
using the van’t Hoff’s law, in the elongating tissues but the levels in mature tissues increased in vermiculite with a low
Ψw. Our results suggest that (1) reductions in root elongation in vermiculite with a low Ψw were caused by reductions in the extensibility and/or increases in the yield threshold of cell walls and by reductions in
the hydraulic conductivity of the tissues; and (2) a seminal root regulates its growth to keep turgor pressure unchanged. |
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Keywords: | growth seminal root solute accumulation turgor water potential wheat |
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