Effects of different nitrogen forms on the growth and cytokinin content in xylem sap of tomato (Lycopersicon esculentum Mill.) seedlings
Effects of different nitrogen forms on the growth and cytokinin content in xylem sap of tomato (Lycopersicon esculentum Mill.) seedlings
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不同氮形态对番茄幼苗生长及木质部汁液细胞分裂素含量的影响
DOI：
10.1007/s11104-008-9733-y
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发表时间：
2009-02-01
期刊：
影响因子：
4.9
通讯作者：
Dong, Cai Xia
中科院分区：
文献类型：
--
作者：
Lu, Ying Lin;Xu, Yang Chun;Dong, Cai Xia
为了研究不同形态氮素（NO3-、NO3- vs NH 4+）均匀定位供应对番茄幼苗生长的影响，分析了根系形态和木质部汁液中6种细胞分裂素（CTK）组分。在均匀供应条件下，以不同比例的NO3-：NH 4+（100：0，100- 0 NA; 75：25，75- 25 NA; 50：50，50- 50 NA）供应全根。在分根试验中，比较了三种处理：单一NO3-供应（N垂直条N），NO3-和NH 4+的空间分离供应（N垂直条A），以及NO3-和NO3-和NH 4+营养的混合物以75：25的比例空间分离供应（N垂直条AN）。结果表明：（1）75%NO3-+25%NH4+均匀供应于整个根区时，地上部和根系干物质（DM）、根表面积（RS）和根体积（RV）最大; NO3-和NH 4+的空间分离供应（N垂直条A）导致对根系形态的对比效应：与N垂直条N相比，含NO3-的盆中根系DM增加了50%，而含NH 4+的盆中根系DM降低了50%。在分根试验中，75%NO3-+25%NH4+处理对地上部干物质、根系干物质、RS和RV的影响均不显著。(2)外源NH 4+的存在导致木质部总CTK浓度显著降低，且无论培养模式如何，木质部NH 4+与总CTK浓度均呈密切的负相关。75- 25 NA和N竖条A处理都维持了较高的玉米素核苷（ZR）水平。由此可见，除了营养液中NH 4+与NO3-的比例外，NH 4+是供给整个根系还是只供给部分根系也是影响植物生长的重要因素。75- 25 NA和N竖条A处理番茄幼苗生长最佳的原因可能是木质部中较高的ZR浓度。
In order to investigate the effects of homogeneous and localized supply of different nitrogen forms (nitrate, NO3- vs ammonium, NH4+) on the growth of tomato seedlings, root morphology and six cytokinin (CTK) fractions in xylem sap were analyzed. Whole roots were supplied with different ratios of NO3- to NH4+ (100: 0, as 100-0NA; 75: 25, as 75-25NA; 50: 50, as 50-50NA) under homogeneous supply. In split-root experiments, three treatments were compared: a sole NO3- supply (N vertical bar N), a spatially separated supply of NO3- and NH4+ (N vertical bar A), and a spatially separated supply of NO3- and a mixture of NO3- and NH4+ nutrition at a ratio of 75:25 (N vertical bar AN). All concentrations of total N were set at 5 mM. The results showed that (1) homogeneous 75% NO3- plus 25% NH4+ supply to the whole root zone led to maximum shoot and root dry matter (DM), root surface area (RS) and root volume (RV). The spatially separated supply of NO3- and NH4+ (N vertical bar A) resulted in a contrasting effect on root morphology: in comparison to N vertical bar N, root DM in the NO3- -containing pot was increased by 50% whereas it was depressed by 50% in the NH4+ -containing pot. The 75% NO3- plus 25% NH4+ supply in the split-root experiment led to no significant effects either on shoot DM and root DM, or on RS and RV when compared to N vertical bar N. (2) The presence of NH4+ in the external medium led to a significantly reduced total xylem-CTK concentration, and a close negative correlation was found between xylem NH4+ and total CTK concentration irrespective of culture mode. A relatively high level of zeatin riboside (ZR) was maintained both in 75-25NA and N vertical bar A treatments. It was concluded that, in addition to the percentage of NH4+ to NO3- in the nutrient solution, whether NH4+ was supplied to the whole root system or to only part of the root system was also an important factor affecting plant growth. The fact that the 75-25NA and N vertical bar A treatments resulted in optimal growth of tomato seedlings might be attributed to the higher ZR concentration in xylem.