Ruan Jianyun, Gerendás Jóska, Härdter Rolf, Sattelmacher Burkhard
Institute for Plant Nutrition and Soil Science, Kiel University, Kiel, D-24098, Germany.
Ann Bot. 2007 Feb;99(2):301-10. doi: 10.1093/aob/mcl258. Epub 2007 Jan 4.
Tea (Camellia sinensis) is considered to be acid tolerant and prefers ammonium nutrition, but the interaction between root zone acidity and N form is not properly understood. The present study was performed to characterize their interaction with respect to growth and mineral nutrition.
Tea plants were hydroponically cultured with NH4+, NO3- and NH(4+) + NO3-, at pH 4.0, 5.0 and 6.0, which were maintained by pH stat systems.
Plants supplied with NO3- showed yellowish leaves resembling nitrogen deficiency and grew much slower than those receiving NH4+ or NH(4+) + NO3- irrespective of root-zone pH. Absorption of NH4+ was 2- to 3.4-fold faster than NO3- when supplied separately, and 6- to 16-fold faster when supplied simultaneously. Nitrate-grown plants had significantly reduced glutamine synthetase activity, and lower concentrations of total N, free amino acids and glucose in the roots, but higher concentrations of cations and carboxylates (mainly oxalate) than those grown with NH4+ or NH(4+) + NO3-. Biomass production was largest at pH 5.0 regardless of N form, and was drastically reduced by a combination of high root-zone pH and NO3-. Low root-zone pH reduced root growth only in NO(3-)-fed plants. Absorption of N followed a similar pattern as root-zone pH changed, showing highest uptake rates at pH 5.0. The concentrations of total N, free amino acids, sugars and the activity of GS were generally not influenced by pH, whereas the concentrations of cations and carboxylates were generally increased with increasing root-zone pH.
Tea plants are well-adapted to NH(4+)-rich environments by exhibiting a high capacity for NH4+ assimilation in their roots, reflected in strongly increased key enzyme activities and improved carbohydrate status. The poor plant growth with NO3- was largely associated with inefficient absorption of this N source. Decreased growth caused by inappropriate external pH corresponded well with the declining absorption of nitrogen.
茶树（Camellia sinensis）被认为耐酸性且偏好铵态氮营养，但根际酸度与氮形态之间的相互作用尚未得到充分理解。本研究旨在表征它们在生长和矿质营养方面的相互作用。
茶树在pH值为4.0、5.0和6.0的条件下，通过pH自动控制系统以NH4+、NO3-和NH(4+) + NO3-进行水培。
无论根际pH值如何，供应NO3-的植株叶片发黄，类似缺氮症状，生长速度比供应NH4+或NH(4+) + NO3-的植株慢得多。单独供应时，NH4+的吸收速度比NO3-快2至3.4倍，同时供应时快6至16倍。以硝酸盐为氮源生长的植株谷氨酰胺合成酶活性显著降低，根中总氮、游离氨基酸和葡萄糖浓度较低，但阳离子和羧酸盐（主要是草酸盐）浓度高于以NH4+或NH(4+) + NO3-为氮源生长的植株。无论氮形态如何，生物量产量在pH 5.0时最大，高根际pH值与NO3-共同作用会使其大幅降低。低根际pH值仅在以NO(3-)为氮源的植株中降低根生长。随着根际pH值变化，氮的吸收呈现相似模式，在pH 5.0时吸收速率最高。总氮、游离氨基酸、糖的浓度以及GS的活性一般不受pH影响，而阳离子和羧酸盐的浓度通常随根际pH值升高而增加。
茶树通过在根中表现出高铵同化能力，很好地适应了富含NH(4+)的环境，这体现在关键酶活性大幅增加和碳水化合物状况改善上。以NO3-为氮源时植株生长不良主要与该氮源吸收效率低下有关。外部pH值不适宜导致的生长下降与氮吸收减少密切相关。
