EVALUATION OF CRITICAL LIMIT OF LOW LIGHT INTENSITY THROUGH PHOTOSYNTHETIC AND PHOTOSYSTEM-II MECHANISMS IN BLACKGRAM (Vigna mungo L.)

MAYANK CHATURVEDI¹*, BADRE ALAM^2
1School of Agriculture, MVN University, Palwal, 121105, Haryana, India
²ICAR-Central Agroforestry Research Institute, Jhansi, 284003, Uttar Pradesh, India
* Corresponding Author : drmayank.chaturvedi@mvn.edu.in

Received : 09-02-2022     Accepted : 27-03-2022     Published : 30-03-2022
Volume : 14     Issue : 3       Pages : 11211 - 11216
Int J Agr Sci 14.3 (2022):11211-11216

Keywords : Inter cellular CO2, In-vivo carboxylation efficiency, Net rate of CO2 assimilation, Photosynthetic photon flux density, Thylakoid electron transport rate
Academic Editor : Maharaj Singh, Dr A. K. Singh
Conflict of Interest : None declared
Acknowledgements/Funding : Authors are thankful to ICAR-Central Agroforestry Research Institute, Jhansi, 284003, Uttar Pradesh, India
Author Contribution : All authors equally contributed

Experiments were carried out to evaluate the impact of low solar irradiance as commonly observed in agroforestry practices on physiological functions of blackgram (Vigna mungo L.). Low solar irradiance brought down regulation of CO2 assimilatory functions, photochemical efficiency and related photosynthetic traits in blackgram. Down regulation of CO2 assimilatory functions was associated with the less photosynthetic electron supply for net CO2 assimilation rate (PN). From the analysis of the photosynthetic photon flux density (PPFD) versus PN response curve and PPFD versus intercellular CO2 (Ci) response curve, it has been clearly demonstrated that compensation irradiance (CI), thylakoid electron transport (ETR), photosynthetic water use efficiency (WUE) and in-vivo carboxylation efficiency (CE) were the major determinants for low solar irradiance induced reduction in physiological functions leading to carbon assimilation. Rate of the PPFD saturated PN (sat) decreased by 2.25% in 67% solar irradiance, whereas, the reduction was as high as 49.52% in 25% solar irradiance. The reduction in ETR was directly corroborated with the reduction in PN and many other photosynthetic traits depending upon the level of solar irradiance captured by understorey crops of agroforestry systems. Our results revealed that blackgram has acclimated CO2 assimilatory function through photosynthetic traits and more importantly by decreasing the compensation irradiance (from 56.42 to 10.10?mol m-2s-1) under low irradiance. It is observed that 67% solar irradiance would be a critical limit for the crop as reduction of yield (%) was relatively low in it than in 50% sun light and 25% sun light when compare to open grown crops

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