Influence Of Nitrogen Form And Their Application Time On Potato Tuber Growth And Its Mechanism

Tuber is the economic organ of potato, its formation time and numbers are directly correlated with the final yield. Therefore, the potato tuberization process and influencing factors are always the hot research topics in plant physiology and agriculture areas. Higher plants are able to take up nitrogen (N) usually in the form of nitrate (NO3") or ammonium (NH4+). Previous studies have found that nitrogen forms affect the potato tuberization, but the detailed result were not consistent. Some studies have reported that the influence of nitrogen forms on potato tuberization was extremely complex, probably it vary depends on the growth period. Basing on this, the effects of different nitrogen form and their application time on the tuber formation time and tubers number were systematically observed by setting three years of pot experiments using different potato varieties, and its possible physiological mechanism was analyzed from the relation of organ hormones metabolism and environmental pH changing with tuber development The nitrogen management strategy for higher yield and high N utilization efficiency was proposed as well in the thesis. Specific results are as follows:1. Nitrogen form has significant influence on the potato tuber formation. Tuber number per plant was significantly influenced by nitrogen form applied before tuberization, plants treated with NO3-N formed more tubers per plant than those treated with NH4-N. However, plant treated with NH4-N develop tubers earlier.2. The nitrogen form applied before tuber formation only influence the growth of early stage of potato plants, can not continuously influence on the growth of later stage of potato. However, plants grow faster and get higher tuber yield under application of NH4-N after tuberization compared with that of NO3-N.3. Nitrogen form applied before tuber formation has no continuous influence on the potato NPK accumulations at later growth stages, however potato NPK accumulations are higher than those under application of NH4-N,which is consistent with the potato dry matter accumulation.4. The influence of different nitrogen forms on tuber formation is not correlated with rhizosphere soil pH changes caused by N absorption.5.rIn this study, the tuber formation influenced by N form has no direct connection with organ phytohormone concentration and their ratio.These results clearly pointed that effects of different nitrogen form on potato tuber formation and the reaction of potato plants at different stages with nitrogen form supply, which can provide the theoretical basis for potato nutrient management and guiding the potato-specific fertilizer development.