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5‐Aminolevulinic acid (ALA), an intermediate of the biological tetrapyrrole synthesis, can be used as a photodynamic herbicide/insecticide. Among the various microorganisms capable of its production, anoxygenic phototrophic bacteria produce ALA in considerable amounts, making it worthwhile to work toward commercial exploitation. Knowledge of the biochemical synthesis of ALA and its physiological and genetic regulation in microorganisms can enable the biotechnologist to manipulate them for enhancing ALA production for possible practical applications.

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Variations in leaf gas-exchange characteristics, leaf pigment content, and other important leaf traits were investigated in seven wild Oryza species, five hybrids and improved varieties. The significant variations were observed in photosynthetic pigment contents amongst different species of Oryza. The mean chlorophyll (Chl) content was higher in O. sativa (varieties and hybrids), while O. eichengeri showed the lowest Chl content. The mean carotenoid (Car) content in O. sativa (varieties and hybrids) was higher than in other wild rice species. O. eichengeri and O. barthii had significantly lower Car contents than other rice species. Significant differences were noticed in the rate of photosynthesis (P N ), stomatal conductance (g s ), transpiration rate (E), internal CO 2 concentration (C i ), specific leaf mass (SLM), and leaf thickness amongst different Oryza species. The mean P N was the highest in O. nivara followed by O. eichengeri. The mean P N was the lowest in O. glumaepatula, which was lower than that of cultivated varieties and hybrids of O. sativa. High rates of photosynthesis were observed in O. nivara (ACC. No. CR 100097), O. rufipogon (ACC.No. CR 100267), and O. nivara (ACC.No. CR 100008). The O. nivara and O. rufipogon genotypes with high P N might be used in rice improvement programmes for an increase of leaf photosynthesis in rice. Multiple correlations performed between different gas-exchange characteristics and other physiological traits revealed that the rate of photosynthesis was not dependent on the leaf pigment content or the leaf thickness. A strong positive correlation between P N and the P N /C i ratio, which represents the carboxylation efficiency, indicated that the observed variation in P N was not based on pigment content or other leaf traits.