Radiation and nitrogen use at the leaf and canopy level by wheat and oilseed rape during the critical period for grain number definition

M.F. Dreccer, A.H.C.M. Schapendonk, M. van Oijen, C.S. Pot, R. Rabbinge

Research output: Contribution to journalArticleAcademicpeer-review

30 Citations (Scopus)

Abstract

During the critical period for grain number definition, the amount of biomass produced per unit absorbed radiation is more sensitive to nitrogen (N) supply in oilseed rape than in wheat, and reaches a higher value at high N. This response was investigated by combining experimental and modelling work. Oilseed rape and wheat were grown at three levels of N supply, combined with two levels of plant density at high N supply. Canopy photosynthesis and daytime radiation use efficiency (RUEA) were calculated with a model based on observed N-dependent leaf photosynthesis and observed canopy vertical distribution of light and leaf N. In oilseed rape, RUEA was higher than in wheat and, in contrast to wheat, the sensitivity to canopy leaf N content increased from the start to the end of the critical period. These results were partly explained by the higher leaf photosynthesis in oilseed rape vs wheat. In addition, oilseed rape leaves were increasingly shaded by the inflorescence. Thus, RUEA increased because more leaves were operating at non-saturating light levels. In both species, the vertical distribution of leaf N was close to that optimising canopy photosynthesis. The results are discussed in relation to possibilities for improvement of N productivity in these crops.
Original languageEnglish
Pages (from-to)899-910
JournalAustralian Journal of Plant Physiology
Volume27
Issue number10
DOIs
Publication statusPublished - 2000

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