The auxin-resistant dgt tomato mutant grows less than the wild type but is less sensitive to ammonium toxicity and nitrogen deficiency.

The low-auxin-sensitivity tomato mutant, dgt , despite displaying reduced plant growth, has been linked to greater resistance to N deficiency. This led us to test the role of auxin resistance of dgt in NH 4 + toxicity and N deficiency, compared to wild type tomato (cv. Micro-Tom, MT), grown in hydroponic media. A completely randomized design with three replications in a 2 × 4 factorial scheme was adopted, corresponding to the two tomato genotypes (MT and dgt), involving four nutritional treatments: NO 3 − (5 mM); NH 4 + (5 mM); NO 3 − (5 mM) plus exogenous auxin (10 μM IAA); and N omission. The results show that NH 4 + was toxic to MT but not to dgt. Under N deficiency, MT displayed a lower shoot NO 3 − content, a lower photosynthetic rate, and a decrease in both shoot and root dry weight. However, in dgt , no difference was observed in shoot NO 3 − content and photosynthetic rate between plants grown on NO 3 − or under N deficiency. In addition, dgt showed an increase in shoot dry weight under N deficiency. We highlight the role of auxin resistance in the adaptation of plants to NH 4 + toxicity and N deficiency. [ABSTRACT FROM AUTHOR]