Premium
Nitrogen allocation in response to partial shading of a plant: Possible mechanisms
Author(s) -
Pons Thijs L.,
Bergkotte Marc
Publication year - 1996
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1996.tb05713.x
Subject(s) - transpiration , shading , photosynthesis , phaseolus , chlorophyll , light intensity , horticulture , nitrogen , biology , botany , specific leaf area , chemistry , art , physics , organic chemistry , optics , visual arts
The significance of photosynthetic and transpiration rates for the perception by plants of light gradients in leaf canopies has been investigated with regard to nitrogen allocation and re‐allocation. A gradient of photon flux density (PFD) over a plant's foliage was simulated by shading one leaf of a pair of primary leaves of bean ( Phaseolus vulgaris L. cv. Rentegever). Photosynthetic rate was manipulated independently of PFD and, to some extent, also of transpiration, by subjecting the leaf to different CO 2 concentrations. Transpiration rate was changed independently of PFD and photosynthetic rate by subjecting the leaf to different vapour pressure differences (VPD). A reduced partial pressure of CO 2 reduced specific leaf mass (SLM) as did a decreased PFD, but did not change leaf N per unit area (N LA ) and light saturated rate of photosynthesis (A max ). A reduced VPD caused several effects consistent with the effect of PFD. It decreased N LA and A max and increased the chlorophyll to N ratio in old and young leaves. Furthermore, it decreased the chlorophyll a to b ratio and inhibited leaf growth in young leaves. The transpiration stream is partitioned among the leaves of a plant according to their transpiration rates. The results suggest that relative rates of import of xylem sap into leaves of a plant play an important role in the perception of partial shading of a plant, a situation normally found in dense vegetations. The possible role of cytokinin influx into leaves as controlled by transpiration rate, is discussed.