Photosynthetic Performance of Ocimum sanctum Morphotypes in a Semiarid Region

ABSTRACT

Comparative ecophysiological studies by measurements of photosystem II (PSII) chlorophyll a fluorescence, pigment composition, and proline content were used in the synecological assessments of two Ocimum sanctum (holy basil) morphotypes, viz., Sri Tulsi and Krishna Tulsi, to compare their overall “adaptiveness.” The effective quantum yield of PSII (ΔF/F_m’sat) and maximum apparent electron transport rate (ETR_max) was 30% lower in Krishna Tulsi than in Sri Tulsi plants. Chlorophyll and carotenoid content in Sri Tulsi were twofold higher than in Krishna Tulsi. Results indicated that differences in photosynthetic efficiency observed in Sri Tulsi may determine ecological dominance.

KEYWORDS:

• Chl a fluorescence
• photosynthesis
• photosystem II

ABBREVIATIONS:

• Chl
• chlorophyll
• ΔF/F_m’sat
• effective quantum yield of PSII at ETRmax
• PSI
• photosystem I
• PSII
• photosystem II
• ETR_max
• maximum apparent electron transport rate