A study of amino acids absorption and metabolism by some plants
2010
Nihei, N., Fukushima-ken. Agricultural Technology Center, Koriyama (Japan)
We present absorption and metabolism of glutamine by some plants. Rice, wheat, soybean, qing-geng-cai, and cucumber were grown in a culture solution, each containing different kind of 20 amino acids as nitrogen sources under sterile condition. There was a large difference in growing and root development according to the kind of amino acids supplied. Growing was well when glutamine, asparagine or alanine was supplied to the root. Especially, in the case of glutamine, the seminal roots and lateral roots were developed well. On the other hand, inhibition of the growing and root development were shown when cysteine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, serine, threonine, tyrosine and valine were supplied. Then the glutamine absorption manner was analyzed applying sup(14)C-labeled glutamine, using the real-time imaging system we developed. The uptake amount of glutamine was steadily increased at the root tip. However, in the middle of the root, glutamine uptake curve reached plateau after 10 hours, suggesting that the glutamine uptake and accumulation were active at root tip, while the glutamine was only passing through the middle part of the root. To analyze metabolism of glutamine in the plant, doubly labeled glutamine with stable isotopes were used. It was found that the amount of nitrogen derived from glutamine was higher than that of NH4sup(+) in roots. In the case of glutamine uptake, the profile of amino acids in root was rather constant compared to those when the other kind of amino acids were supplied, which suggested the smooth assimilation of absorbed glutamine. Since the absorbed glutamine was estimated to be the starting material for the amino acid synthesis, the utilization of nitrogen from glutamine was supposed to induce good morphological development of roots.
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