Effects of nitrogen supply on bulb development in onion Allium cepa L

• Published in: Journal of experimental botany Vol. 40; no. 219; pp. 1155 - 1162
• Main Authors: Brewster, J.L, Butler, H.A
• Format: Journal Article
• Language: English
• Published: Oxford Oxford University Press 01-10-1989
• Subjects: Agronomy. Soil science and plant productions; Allium cepa; Biological and medical sciences; bulbing; daylength; Developmental biology; Economic plant physiology; Fundamental and applied biological sciences. Psychology; Growth and development; Leaf blade; Leaves; Morphogenesis, differentiation, rhizogenesis, tuberization. Senescence; Nitrates; Nitrogen; Onion; Onions; Photoperiod; Plant bulbs; plant development; Plant growth. Development of the storage organs; Plant physiology and development; Plants; ripening; Sowing; temperature; Vegetative apparatus, growth and morphogenesis. Senescence; Culture medium; Allium cepa; Monocotyledones; Nitrates; Photoperiod; Nitrogen; Field experiment; Liliaceae; Vegetable crop; Bulb; Angiospermae; Spermatophyta; Developmental stage
• ISSN: 0022-0957; 1460-2431
• DOI: 10.1093/jxb/40.10.1155

Onions were sub-irrigated with 0.6, 2.4, 4.8 and 12 mol m-3 nitrate while growing in constant photoperiods of 14, 15 or 16 h. The lower the nitrogen, the later bulb scale initiation occurred and in 14 h photoperiods bulb scale, initiated only at the highest N level. In the early stages of the experiment, the ratio bulb width/neck width was higher in low N than in high N treatments, but the reverse was true at the later harvests, by which time bulb scales had formed. In a second experiment onions were sub-irrigated continuously with 0.6 mol m-3 or 12 mol m-3 nitrate or transferred from the low to high, or from high to low N after 36 d of growth in 14, 15.25 and 17 h photoperiods. An initial period of low N delayed bulb scale development and ripening relative to high N throughout, particularly under 14 h photoperiods. Late N deprivation did not prevent or delay bulb scale initiation or ripening. In a field experiment, plants not fertilized before sowing but given the total quantity of N late in the growing season formed mature bulbs later than plants fertilized with N before sowing, or given half the quantity of N before sowing and the second half late in the growing season.