C4 Equivalent Decarboxylation Competence in Tropical Orchids

Abstract Tropical xero-epiphytic orchids undergo a photosynthetic mechanism called ‘Crassulacean Acid Metabolism’, a modification of Calvin–Benson cycle. This anabolic process aids in the long-term retention of organically fixed CO 2 , imprinting them as active sequestrators and fixers of gaseous CO 2 . The malate decarboxylation competence of enzymes—phosphoenolpyruvate carboxykinase (PEPCK), Nicotinamide Adenine Dinucleotide malic enzyme (NAD-ME) and Nicotinamide Adenine Dinucleotide Phosphate malic enzyme (NADP-ME) in xero-epiphytic orchids that concentrate CO 2 by employing RuBisCO to embark on a carboxylation route is defined in this paper. Physiological parameters like photosynthetic rates, and quantum yield, accompanied by histomorphometry were analysed. Our study indicated PEPCK as the dominant decarboxylating enzyme in tropical orchids. The efficiency of PEPCK was reinforced by two additional malic enzymes, which are dependent on cofactors, namely Nicotinamide Adenine Dinucleotide and Nicotinamide Adenine Dinucleotide Phosphate. These results indicated the need to appraise the potential of tropical orchids as strategic plant contenders for CO 2 triggered greenhouse effect mitigator.