Measurement and modelling of photosynthetic response of pearl millet to soil phosphorus addition

Payne, W A and Drew, M C and Hossner, L R and Lascano, R J (1996) Measurement and modelling of photosynthetic response of pearl millet to soil phosphorus addition. Plant and Soil, 184 (1). pp. 67-73. ISSN 0032-079X

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Abstract

There have been no studies of the effects of soil P deficiency on pearl millet (Pennisetum glaucum (L.) R. Br.) photosynthesis, despite the fact that P deficiency is the majorxonstraint to pearl millet production in most regions of West Africa. Because current photosynthesis-based crop simulation models do not explicitly take into account P deficiency effects on leaf photosynthesis, they cannot predict millet growth without extensive calibration. We studied the effects of soil addition on leaf P content, photosynthetic rate (A), and whole-plant dry matter production (DM) of non-water-stressed, 28 d pearl millet plants grown in pots containing 6.00 kg of a P-deficient soil. As soil P addition increased from 0 to 155.2 mg P kg- 1 soil, leaf P content increased from 0.65 to 7.0 g kg-1 . Both A and DM had maximal values near 51.7 mg P kg- 1 soil, which corresponded to a leaf P content of 3.2 g kg- 1. Within this range of soil P addition, the slope of A plotted against stomatal conductance (gs) tripled, and mean leaf internal CO2 concentration ([CC^];) decreased from 260 to 92 pL L~'., thus indicating that P deficiency limited A through metabolic dysfunction rather than stomatal regulation. Light response curves of A, which changed markedly with P leaf content, were modelled as a single substrate, Michaelis-Menten reaction, using quantum flux as the substrate for each level of soil P addition. An Eadie-Hofstee plot of light response data revealed that both Km, which is mathematically equivalent to quantum efficiency, and Vmax, which is the light-saturated rate of photosynthesis, increased sharply from leaf P contents of 0.6 to 3 g kg-1 , with peak values between 4 and 5 g P kg-1 . Polynomial equations relating Km and Vmax, to leaf P content offered a simple and attractive way of modelling photosynthetic light response for plants of different P status, but this approach is somewhat complicated by the decrease of leaf P content with ontogeny.

Item Type:	Article
Divisions:	UNSPECIFIED
CRP:	UNSPECIFIED
Uncontrolled Keywords:	pearl millet, Pennisetum glaucum (L.) R. Br., phosphorus, photosynthesis, modelling
Subjects:	Mandate crops > Millets Others > Soil Science
Depositing User:	Mr Siva Shankar
Date Deposited:	14 Mar 2014 05:53
Last Modified:	14 Mar 2014 05:53
URI:	http://oar.icrisat.org/id/eprint/7616
Official URL:	http://dx.doi.org/10.1007/BF00029275
Projects:	UNSPECIFIED
Funders:	UNSPECIFIED
Acknowledgement:	UNSPECIFIED
Links:	Google Scholar

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