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Carbon balancing within the plant species is an important feature for climatic adaptability. Photosynthesis and respiration traits are directly linked with carbon balance. These features were studied in 20 wild rice accessions Oryza spp., and cultivars. Wide variation was observed within the wild rice accessions for photosynthetic oxygen evolution or photosynthetic rate (A), dark (R d ), and light induced respiration (LIR) rates, as well as stomatal density and number. The mean rate of A varied from 10.49 lmol O 2 m -2 s -1 in cultivated species and 13.09 lmol O 2 m -2 s -1 in wild spp., The mean R d is 2.09 lmol O 2 m -2 s -1 and 2.31 lmol O 2 m -2 s -1 in cultivated and wild spp., respectively. Light induced Respiration (LIR) was found to be almost twice in wild rice spp., (16.75 lmol O 2 m -2 s -1 ) compared to cultivated Oryza spp., Among the various parameters, this study reveals LIR and A as the key factors for positive carbon balance. Stomatal contribution towards carbon balance appears to be more dependent on abaxial surface where several number of stomata are situated. Correlation analysis indicates that R d and LIR increase with the increase in A. In this study, O. nivara (CR 100100, CR 100097), O. rufipogon (IR 103404) and O. glumaepatula (IR104387) were identified as potential donors which could be used in rice breeding program. Coordination between gas exchange and patchiness in stomatal behaviour appears to be important for carbon balance and environmental adaptation of wild rice accessions, therefore, survival under harsh environment.

With the priority of the low input sustainable rice cultivation for environment friendly agriculture, NUE of rice becomes the need of the hour. A set of 472 rice genotypes comprising landraces and breeding lines were evaluated for two seasons under field conditions with low and recommended nitrogen and >100 landraces were identified with relative higher yield under low nitrogen. Donors were identified for higher N uptake, N translocation into grains and grain yield under low N. Grains on secondary branches, N content in grain and yield appears to be the selection criterion under low N. Through association mapping, using minimum marker set of 50 rice SSR markers, 12 genomic regions were identified for yield and yield associated traits under low nitrogen. Four associated genomic regions on chromosomes 5, 7 and 10 were fine mapped and QTL for yield under low N were identified from the marker delimited regions. Three candidate genes viz., 2-oxoglutarate /malate translocator (Os05g0208000), alanine aminotransferase (Os07g0617800) and pyridoxal phosphate-dependent transferase (Os10g0189600) from QTL regions showed enhanced expression in the genotypes with promising yield under low N. Marker assisted selection using SSR markers associated with three candidate genes identified two stable breeding lines confirmed through multi-location evaluation.

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Influence of 24-epibrassinolide and 28-homobrassinolide on the growth of coleus [Plectranthus forskohlii; Lamiaceae] was investigated. Application of brassinosteroids enhanced the growth in terms of plant height, leaf number, leaf area, and the dry weight of shoots and leaves. Among all the treatments, 28-homobrassinolide at 3µM concentration was highly effective in enhancing the growth. A two-fold increase in shoot dry weight and 2.4 times increase in leaf area was observed in coleus plants treated with 3µM concentration of 28-homobrassinolide. Application of brassinosteroids also increased the rate of photosynthesis, levels of chlorophyll pigments, and various carbohydrate fractions. The tuberous root yield of coleus plants was found to be increased in plants treated with brassinosteroids. 28-homobrassinolide (3µM concentration) proved to be highly efficient and accounted for a twofold increase in tuberous root yield. HPLC analysis revealed the increase in forskolin content in the roots of brassinosteroid-treated plants. Tuberous roots obtained from coleus plants treated with 28-homobrassinolide contained 0.17% forskolin as compared to 0.098% in the roots of untreated control plants.