Kumar, Amit and Kumar, Neeraj and Ahuja, Paramvir Singh (2006) Effect of altitude on the primary products of photosynthesis and the associated enzymes in barley and wheat. Photosynthesis Research, 88. pp. 63-71.

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Abstract

There is little information available on the primary products of photosynthesis and the change in the activity of the associated enzymes with altitude. We studied the same in varieties of barley and wheat grown at 1300 (low altitude, LA) and 4200 m (high altitude, HA) elevations above mean sea level in the western Himalayas. Plants at both the locations had similar photosynthetic rates, leaf water potential and the chlorophyll fluorescence kinetics. The short-term radio-labelling experiments in leaves showed appearance of 14CO2 in phosphoglyceric acid and sugar phosphates in plants at both the LA and HA, suggesting a major role of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) in CO2 fixation in the plants at two altitudes, whereas the appearance of labelled carbon in aspartate (Asp) and glutamate (Glu) at HA suggested a role of phosphoenolpyruvate carboxylase (PEPCase) in photosynthesis metabolism. Plants at HA had significantly higher activities of PEPCase, carboxylase and oxygenase activity of Rubisco, aspartate aminotransferase (AspAT), and glutamine synthetase (GS). However, the activities of malate dehydrogenase, NAD-malic enzyme and citrate synthase were similar at the two locations. Such an altered metabolism at HA suggested that PEPCase probably captured CO2 directly from the atmosphere and/or that generated metabolically e.g. from photorespiration at HA. Higher oxygenase activity at HA suggests high photorespiratory activity. OAA thus produced could be additionally channelised for Asp synthesis using Glu as a source of ammonia. Higher GS activity ensures higher assimilation rate of NH3 and the synthesis of Glu through GS-GOGAT (glutamine:2-oxoglutarate aminotransferase) pathway, also as supported by the appearance of radiolabel in Glu at HA. Enhanced PEPCase activity coupled with higher activities of AspAT and GS suggests a role in conserving C and N in the HA environment.

Item Type:	Article
Uncontrolled Keywords:	high altitude, photosynthesis, photosynthetic enzymes, primary products of photosynthesis
Subjects:	Plant sciences Plant Biotechnology Ecology
Divisions:	UNSPECIFIED
Depositing User:	Dr. Aparna Maitra Pati
Date Deposited:	29 Dec 2011 07:05
Last Modified:	07 Feb 2012 10:33
URI:	http://ihbt.csircentral.net/id/eprint/120

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