Showing papers on "Sesbania rostrata published in 1999"

Reverse flow in roots of Sesbania rostrata measured using the constant power heat balance method

Abstract: This investigation was performed to examine qualitatively and quantitatively the reverse flow in partially dried roots of Sesbania rostrata using the constant power heat balance method. First, a semi-empirical technique for estimating sheath conductance of sap-flow sensors without assuming that sap flow is zero at night was proposed. Sap flow measured with the heat balance method was compared with water uptake as measured by a potometric method. Sap flow was overestimated by 56·1% for a 3·3-mm-diameter root, and by 40·0% for 6·1 mm and 33·3% for 8·8 mm roots. However, high correlation coefficients between the rates of water uptake and sap flow demonstrated that calibration would provide reliable values for root sap flow. To detect reverse flow, a split root experiment was conducted using a S. rostrata plant with its root system divided between dry and wet compartments. Daily sap flow of the drying compartment declined whereas that in ‘wet’ root increased, suggesting that the decrease in water uptake by ‘dry’ roots was offset by the ‘wet’ roots. Reverse flow was observed at night in the root on the dry side of the container when the soil water potential was less than –0·30 MPa. The total amount of water released into the soil during the night period was estimated to be 22·5 g.

Diversity of Rhizobia Nodulating Crotalaria spp. from Senegal

Abstract: A total of 117 rhizobia strains was isolated from root nodules of nine Crotalaria spp. Nodules were collected at eight geographical sites in Senegal. Growth in yeast mannitol agar (YMA) revealed that rhizobia strains of Crotalaria spp. include both fast and slow-growing strains. Host-specificity shows two groups of specificity in Crofalaria spp. tested: group I includes C. glaucoides, C. perrottefii and C. podocarpa which were effectively nodulated only by fast-growing strains, and group II includes C. comosa, C. goreensis, C. hyssopifolia, C. lathyroides, C. ochroleuca, C. refusa which were effectively nodulated only by slow-growing strains. Slowgrowing rhizobia have a broad host range and nodulated Crofalaria of group I1 and Acacia albida and Indigofera microcarpa, while fast-growing strains nodulated only Crofalaria spp. None of the strains effectively nodulated Sesbania rostrata or Acacia raddiana. Numerical analysis of whole cells proteins profiles of these strains obtained by SDSPAGE shows that slow-growing strains are related to

Chalcone reductase-homologous transcripts accumulate during development of stem-borne nodules on the tropical legume Sesbania rostrata.

Abstract: During a search for genes with induced or enhanced expression in the early stages of development of stem-borne nodules on Sesbania rostrata, a cDNA with homology to chalcone reductase (CHR) genes was isolated. Here, we describe the characterization of a full-length CHR cDNA (Srchr1) and the pattern of CHR transcript accumulation in stem-borne nodules. Expression was correlated with both nodule development and bacterial invasion. In young nodules, CHR transcripts were observed in cells of the parenchyma, in cells around the nodule vascular bundles, and in the uninfected cells of the central tissue.

Xylem Colonization of Sesbania Rostrata by Azorhizobium Caulinodans ORS571

Abstract: Benign, non-rhizobial, endophytic bacteria probably exist in the xylem of many healthy plants (Bell et al., 1995; Kloepper et al., 1992), including legumes (Gagne et al., 1987). Agrobacteria, plant pathogens related closely to Rhizobium (Young, 1992), can move through the xylem of the legume Sesbania rostrata (Vlachova et al., 1987). The present study assessed the endophytic behaviour of Azorhizobium caulinodans ORS571, in non-nodular tissues of its host, S. rostrata. ORS571 colonized xylem elements, in addition to invading the nodules of this plant.

Uptake of 15N by wetland rice in response to application of 15N-labelled Sesbania rostrata and urea

Abstract: Pot experiments were carried out to evaluate the response of rice to Sesbania rostrata green manure N as compared to urea fertilizer N under flooded conditions. After growing S. rostrata for 21 days with a 15N-labelled N source, the labelled Sesbania was applied to wetland rice as a green manure and the uptake of 15N from this substrate was compared to that from labelled urea. Rice was cultivated twice in the same pots. The rice was grown for a period of 49 days in each case, separated by a period of 21 days when the soil was allowed to dry. The 15N content of the soil and shoots and roots of rice was determined and 15N balances established. The total N content of the shoots and roots of rice was determined by a non-tracer method. The percentage recovery of 15N from shoot material which was derived from urea N was more than twice that from S. rostrata. The recovery of 15N from the pots receiving both green manure and urea was low, and not significantly different from that recovered from the green manure treatment. As much as 64.5–73.5% and 40.1–41% of the 15N remained in the soil which had received green manure or urea, respectively. The overall recoveries of 15N varied between 86.5% and 94.4%. At the second harvest, the oven-dry weight of shoots was significantly (P<0.05) higher in green-manure treated pots, but the total N content did not differ significantly. Labelled N remaining in the soil after amendment with the green manure was much more available to the rice crop than that remaining after the addition of urea-N. The total recovery of labelled N (shoots plus roots) amounted to 65.5% and 74%, respectively of the residual labelled N in the two S. rostrata treatments (i.e. 19.55 mg 15N pot–1 and 39.10 mg 15N pot–1) and 23.2% and 23.2% of the residual labelled N in the two urea treatments (i.e. 19.55 mg 15N pot and 39.10 mg 15N pot–1), respectively.

PII and GlnK Control Ammonia Assimilation and Nitrogen Fixation in Azorhizobium Caulinodans

Abstract: Azorhizobium caulinodans fixes nitrogen both in the free-living state (Nif+) and in symbiosis (Fix+) with its host plant, Sesbania rostrata (Elmerich, et al., 1982). In the free-living state, all the fixed nitrogen is assimilated through the glutamine synthetase enzyme (GS) for the bacteria growth, suggesting a coordination between ammonia assimilation and nitrogen fixation.