Leaf Emergence, Tiller Growth, and Apical Development of Nitrogen‐Dificient Spring Wheat

Conflicting reports exist about the effect of N supply on the rate of leaf emergence. We examined effects of N deficiency on leaf and tiller emergence, tiller initiation and apical development in ‘Aroona’ and ‘Gamenya’ spring wheat ( Triticum aestivum L.). Four levels of N (e.g., 50 μM N = N 50 ) were supplied by hourly irrigation with complete nutrient solution of plants growing in sand. The control plants in Exp. 1 (N 1600 ) had 64 g kg ‐1 N intheshoots at the two‐leaf stag e, compared with 33 in N 50 , 50 in N 300 , and 58 in N 800 . Compared with control plants, dry matter of N 50 plants was 10%, N 300 50%, and N 800 80%. Results in Exp. 2 were similar. The rate of leaf emergence was decreased in all N 50 ‐treated and some N 200 ‐treated plants, but not or N 300 ‐treated plants. Tiller bud initiation was decreased in the treatment. The number of tiller buds was correlated with total number of leaves; if a leaf emerged, N deficiency did not affect tiller initiation. Nitrogen treatment did not alter the sequence of tiller emergence, but tiller emergence was delayed or did not occur in N 50 , N 200 , and N 300 plants. Nitrogen treatment had little effect on the rate of apical development. The double‐ridge stage of development was delayed ≈2 d for both cultivars at the two lowest N treatments. Terminal spikelet production was also delayed by ≈2 d at these N treatments in Aroona, but not in Gamenya spring wheat. The rate of primordia initiation was decreased in N 50 and N 300 plants, resulting in fewer spikelet primordia. The level of N deficiency affected plant response to the stress.