ScienceAsia 9 (1983): 245-256 |doi: 10.2306/scienceasia1513-1874.1983.09.245

EFFECTS OF NITROGEN STRESS ON NITROGEN REDISTRIBUTION AND PHOTOSYNTHESIS IN SOYBEANS

PREEDA BOON-LONG,^a D.B. EGLI and J.E. LEGGETT

ABSTRACT: The effect of N stress on the redistribution of N from soybean leaves (Glycine max (L.) Merrill) was investigated by growing soybeans (cv. 'Cutler 71') in nutrient solutions with varying N Levels in the greenhouse and measuring the ¹⁴C0₂ uptake rate, the levels of total N, Ribulose 1,5 - bisphosphate carboxylase (RuBPCase) and its activity, and 1 N NaOH extractable protein in the leaves. When the plants were subjected to varying levels of N stress for 63 days after emergence, leaf N levels rangedfrom 2. 7 to 13.6 mg.dm^-2 and the C0₂ uptake rate was closely correlated with the variation in leaf N levels. N stress during seed fill (no N in the nutrient mediafrom growth stage R5 to maturity) enhanced the senescence process and the redistribution of N compounds from the leaves. The stressed plants reached physiological maturity 8 days sooner than the control and the levels of N, protein and RuBPCase from growth stage R5 to maturity was similar for both treatments. RuBPCase activity was most sensitive to N stress. Its significant decrease was observed prior to changes in.C0₂ uptake rate and total protein.

Download PDF

Department of Agronomy, University of Kentucky, Lexington, KY 40546-0091, USA.
a.Present address: Department of Botany, Faculty of Science, Chulalongkorn University, Bangkok 10500, Bangkok

Received 18 July 1983