Ammonium toxicity development in tomato plants relative to nitrogen form and light intensity

Ammonium toxicity development in tomato plants relative to nitrogen form and light intensity

1984

REP.TM-0652

Tomato plants were grown in sand culture with NH4+ and NO3- forms of N and three levels of light established by using shade cloth. Plants supplied with NH4+ nutrition under high light intensity showed symptoms of stunting, leaf-roll, wilting, interveinal chlorosis of the older leaves, and produced on third the dry weight of NO3-fed plants. In contrast, plants receiving NH4+ nutrition with light reduced over 50% appeared normal. NH4-N increased NH4 and free amino acid contents of the tissue as compared to NO3-N nutrition. With shading there was a greatly decreased level of free NH4 and increased levels of free amino acids, mainly asparagine and glutamine, in shoots of NH4-treated plants. The NO3 content in shoots of NO3-treated plants increased sharply with shade. The results suggest that the increased NH4 concentration in leaves from photorespiration can be a major factor in the ammonium toxicity expression under high light intensity. [AS]

v.7(10):1477-1496, JOURNAL OF PLANT NUTRITION

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