Are phloem amino, acids involved in the shoot to root control of NO3- uptake in Ricinus communis plants?

被引:49
作者
Tillard, P [1 ]
Passama, L [1 ]
Gojon, A [1 ]
机构
[1] ENSA M, INRA, CNRS, UM2,URA 2133, F-34060 Montpellier 1, France
关键词
N-deficiency; NO3-; uptake; phloem amino; acids; Ricinus communis; whole plant signalling;
D O I
10.1093/jexbot/49.325.1371
中图分类号
Q94 [植物学];
学科分类号
071001 ;
摘要
The putative role of phloem amino acids as negative feedback signals for root NO3- uptake was investigated in Ricinus communis L, The NO3--grown plants were subjected to N-deficiency due either to complete N-deprivation, or to localized N-deprivation on one side of a split-root system. in comparison with controls, complete N-deprivation resulted in a transient increase in (NO3-)-N-15 influx, and in profound changes in downward phloem transport of amino acids. Total amino acid concentration in the phloem sap decreased by 40%, but responses markedly differed between the individual amino acids. Concentrations of Gln and Ser were rapidly lowered by 50%, while those of Val, Phe, Leu, and lie displayed a marked increase. Localized N-deprivation on one side of the split root system also resulted in the up-regulation of (NO3-)-N-15 influx in the roots still supplied with NO3-. However, the amino acid composition of the phloem sap directed to these roots was not modified by the treatment, and remained similar to that in N-sufficient control plants. Only amino acid transport to the N-deprived roots was affected as observed in response to complete N-deprivation. The results from split-root plants indicate that the response of root NO3- influx to N-deficiency is controlled by shoot-borne regulatory signals, and provide a case study where these signals are not related to a qualitative change or a significant decrease in downward phloem transport of amino acids.
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页码:1371 / 1379
页数:9
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