Effects of nitrogen supply on xylem cytokinin delivery, transpiration and leaf expansion of pea genotypes differing in xylem-cytokinin concentration
Effects of nitrogen supply on xylem cytokinin delivery, transpiration and leaf expansion of pea genotypes differing in xylem-cytokinin concentration
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DOI：
10.1071/fp04044
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发表时间：
2004-01-01
影响因子：
3
通讯作者：
Beveridge, CA
中科院分区：
文献类型：
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作者：
Dodd, IC;Ngo, C;Beveridge, CA
rms 2和rms 4豌豆（PisumsativumL.）分支突变体相对于野生型（WT）植物分别具有较高和较低的木质部细胞分裂素浓度。这些基因型生长在两个水平的氮（N）供应18 - 20天，以确定是否或不木质部细胞分裂素浓度（X-CK）或交付改变蒸腾和叶片生长响应N剥夺。木质部汁液通过加压去顶根系收集。随着树液流速的增加，X-CK在WT和rms 2中下降，但在rms 4中没有变化。当生长在5.0 mM N，X-CKs的rms 2和rms 4分别高36%和低6倍，分别比WT在树液流率相当于全株蒸腾。光周期细胞分裂素（CK）的交付率（蒸腾和X-CK的产品）下降了6倍以上的rms 4。植物生长在0.5 mM N对WT和rms 4中以叶面积为基础表示的蒸腾速率的影响可以忽略不计（< 10%），但降低了rms 2的蒸腾速率。低氮处理使叶片展幅降低20 - 25%，展叶氮浓度降低15%。这些变化在所有基因型中是相似的。在树干液流率相当于全株蒸腾，低N处理降低X-CK在rms 2，但在WT和rms 4没有明显的影响。由于低氮处理降低了所有基因型的蒸腾速率，因此所有基因型的光周期CK释放速率也降低。尽管绝对和相对X-CKs和交付的差异，所有基因型对N剥夺的相似的叶片生长反应表明，芽N状态在调节叶片扩展比木质部提供的细胞分裂素更重要。减少X-CK和蒸腾速率的rms 2以下N剥夺表明，木质部提供的CKs的变化可能会修改水分利用。
The rms2 and rms4 pea ( Pisum sativum L.) branching mutants have higher and lower xylem-cytokinin concentration, respectively, relative to wild type (WT) plants. These genotypes were grown at two levels of nitrogen (N) supply for 18 - 20 d to determine whether or not xylem-cytokinin concentration (X-CK) or delivery altered the transpiration and leaf growth responses to N deprivation. Xylem sap was collected by pressurising de-topped root systems. As sap-flow rate increased, X-CK declined in WT and rms2, but did not change in rms4. When grown at 5.0 mM N, X-CKs of rms2 and rms4 were 36% higher and 6-fold lower, respectively, than WT at sap-flow rates equivalent to whole-plant transpiration. Photoperiod cytokinin (CK) delivery rates ( the product of transpiration and X-CK) decreased more than 6-fold in rms4. Growth of plants at 0.5 mM N had negligible (< 10%) effects on transpiration rates expressed on a leaf area basis in WT and rms4, but decreased transpiration rates of rms2. The low-N treatment decreased leaf expansion by 20 - 25% and expanding leaflet N concentration by 15%. These changes were similar in all genotypes. At sap-flow rates equivalent to whole-plant transpiration, the low N treatment decreased X-CK in rms2 but had no discernible effect in WT and rms4. Since the low N treatment decreased transpiration of all genotypes, photoperiod CK delivery rates also decreased in all genotypes. The similar leaf growth response of all genotypes to N deprivation despite differences in both absolute and relative X-CKs and deliveries suggests that shoot N status is more important in regulating leaf expansion than xylem-supplied cytokinins. The decreased X-CK and transpiration rate of rms2 following N deprivation suggests that changes in xylem-supplied CKs may modify water use.