Nitrogen Uptake and Distribution in Oncidium Gower Ramsey
Date Issued
2012
Date
2012
Author(s)
Kuo, Yi-Ai
Abstract
Cut flower production of Oncidium is the second largest orchid industry in Taiwan. The enlarged pseudobulbs, which store nutrients and are interconnected between generations, present difficulties in nutrition research. In this study, the stable isotope of nitrogen was used as a tracer to understand how Oncidium absorbs nitrogen in the fertilizer, nitrogen be allocated in the plant, and the nitrogen form it prefers. It is hoped that the results of this study will provide useful information for improving the fertilization management of Oncidium at different growth stages, so that the quality of Oncidium Gower Ramsey cut flower and the earning of growers may be increased.
After 12 hours of application of fertilizer, nitrogen can be absorbed by the roots and translocated to various parts of Oncidium Gower Ramsey. The leaves, tissue of pseudobulb, and roots of Oncidium Gower Ramsey all have nitrate reductase activities. The activity was highest in the roots, and second highest in the leaves. The nitrate reductase activity of roots decreased with increased age of roots. Under 25/20 oC day/night temperature, the nitrate reductase activities in root of Oncidium was the highest, and it was favorable for Oncidium to absorbed nitrogen. When three kinds of nitrogen sources of urea, ammonium, and nitrate were given at the same time, the roots of Oncidium Gower Ramsey absorbed the three nitrogen forms in the proportion of 0.75：0.57：1, indicating that nitrate was the preferred form of nitrogen for absorption by the roots.
Bud stage and plantlet stage are the vegetative stage of Oncidium Gower Ramsey. Fertilizer nitrogen supplied during the vegetative stage of Oncidium Gower Ramsey was used mainly for the development of the current pseudobulb. The remaining nitrogen was stored in the older pseudobulbs. The nitrogen stored in the pseudobulbs at the vegetative stage was partially allocated to stalk for its development during the reproductive stage. Unsheathing stage and pseudobulb with inflorescence stage are the reproductive stage of Oncidium Gower Ramsey. Most of the fertilizer nitrogen supplied during the reproductive stage was allocated to support stalk development, while the remaining was stored in the pseudobulbs. It indicated that the main nitrogen source of inflorescence was from the nitrogen absorbed during the later phase. During the reproductive stage of the next generation, the nitrogen allocated to the stalk came partly from nitrogen stored in the previous generation, while the majority came from the nitrogen absorbed during the reproductive stage of the current generation.
In summary, the nitrate reductase activity of roots was the highest among organs of Oncidium Gower Ramsey, and roots preferred nitrate in nitrogen uptake. Therefore increasing the proportion of nitrate is recommended for fertilization applied to the roots. Under 25/20 oC day/night temperature, it was favorable for Oncidium to absorbed nitrogen. Reducing the application of nitrogen during reproductive stage is commonly practiced by growers with the intention to increase the rate of stalk emergence. However, this study shows that the source of nitrogen for development of the stalk came mostly from fertilizer applied during the reproductive stage. Therefore, it is important to continue the supply of nitrogen during the reproductive stage of Oncidium Gower Ramsey to improve the quality of cut flower produced and the development of the next generation.
Subjects
nitrogen
isotope
Oncidium
SDGs
Type
thesis
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