Many species of the genus Cenchrus, with different ploidy are important components of world grasslands. In the present investigation, influence of ploidy on leaf water potential (W leaf ) and photosynthetic characteristics under water-stress condition was studied in 2-month-old plants of eight Cenchrus species representing three ploidy and two life spans. Stress was imposed for 2, 4, 6, and 8 days by withholding watering. Decrease in water potential, chlorophyll content, photosynthetic rate (P N ), stomatal conductance for CO 2 (g s ), and carboxylation efficiency (P N /C i ) occurred in all species. Nevertheless, perennial and diploid C. setigerus maintained the highest P N /C i at maximum stress indicating its higher assimilation potential. Photosynthetic water use efficiency (P N /E) in general decreased with increase of water stress; however, at low stress, reverse trend was observed in diploid C. prieurri, C. setigerus, and tetraploid C. glaucus. Results indicate that relative reduction in photosynthetic characteristics was more in annual diploid than perennial diploid and tetraploid. Stress tolerance in terms of plant height, rolling and wilting of leaves also indicated better adaptability of tetra and hexaploid species over diploid. Moreover, recovery of different physiological traits was more pronounced in perennial tetraploid and hexaploid over annual diploid, thus making them suited more to drought conditions. Analysis of variance results showed direct correlation (r = 0.675) of ploidy with gas exchange parameters indicating better impact of this on physiological performance of different species of Cenchrus under water stress. This is the first report where influence of ploidy levels on photosynthetic characteristics and overall responses to moisture stress is studied in a tropical grass species.
Field trials were conducted to determine the effect of algal biofertilizers (Aulosira fertilissima and Anabaena doliolum), alone or in combination with different doses of N-fertilizer (0–120 kg N/ha) supplied as urea, on biomass yield and nutritive value of rice. All doses of N-fertilizer, together with A. fertilissima or A. doliolum, significantly increased plant height, number of tillers/hill, root length, leaf length, chlorophyll content, number of panicles/hill, number of seeds/ear, seed weight, grain yield, protein, and N content of grain. However, lower doses of N-fertilizer resulted in more efficient and rapid responses. Maximal qualitative improvement in rice production was found with 90 kg N/ha together with 12.5 kg/ha algal biofertilizer. The responses to these biofertilizers appear to be strain-specific since application of A. fertilissima yielded better results than application of A. doliolum. Application of the former saved about 25% of the chemical N-demand of the crop.
Cenchrus (family Poaceae) is an important component of major grass covers of the world. Largely it is apomictic and both annual and perennial species exist in nature. Variations in contents of malondialdehyde, proline, specific leaf area and carbon isotope discrimination for drought tolerance were estimated among eight prominent species of Cenchrus. Simultaneously, genetic variations were also estimated by employing 187 RAPD primers. Of these, 23 primers did not react, 2 performed poorly and 7 produced many non-scorable bands and one primer yielded a single monomorphic band. Rest of the 154 primers generated one or more unambiguously scorable fragments. Twelve hundred and four of the 1,296 putative loci were polymorphic (93%) between at least one pair-wise comparisons among eight species. Dice coefficient and neighbor-joining algorithm analyses showed clustering patterns that fit with the known habitat of the species except perennial, C. myosuroides which formed a node between two annuals species. When these species were subjected to water stress tolerance test, a correlation (r = 0.612) between specific leaf area (SLA) and carbon isotope discrimination (CID) and difference in levels of drought tolerance based parameters among eight species were observed. Of the eight species investigated two annuals viz., C. biflorus and C. echinatus showed highest level of genetic similarity which was also evident from the similar levels of SLA, MDA, proline contents and carbon isotope discrimination values observed in these two species.
The isoenzymes of LDH were detected by polyacrylamide gel electrophoresis. The M and H LDH subunits were present in gonads of both sexes from Day 14 1/2 p.c. and there was some variation with increased gestation. From Day 20 after birth two specific LDH-X bands (X1 and X2) were evident in the spermatocyte-rich fraction, but not in those of the Sertoli and Leydig cell fractions or those of the ovary.
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