Land surface phenology as an indicator of biodiversity patterns

With the rapid decline in biodiversity worldwide it is imperative to develop procedures for assessing changes in biodiversity across space. The synoptic view provided by imaging remote sensors constitutes a suitable approach for analyzing biodiversity from local to regional scales. A procedure based on the close relationship between floristic similarity and the similarity in land surface phenology was recently developed and successfully applied to assess diversity patterns using time series imagery acquired by the Moderate Resolution Imaging Spectro-radiometer (MODIS). However, as it depends on high temporal resolution remotely sensed data (e.g., MODIS), the procedure is constrained by the coarse spatial resolution characterizing these high temporal resolution data. Using an optimized technique for image fusion, we combined high temporal resolution data acquired by the MODIS sensor system with moderate spatial resolution data acquired by the Landsat TM/ETM+ sensor systems. Our results show that the MODIS/Landsat data fusion allows the characterization of land surface phenology at higher spatial resolutions, which better corresponded with information acquired within vegetation survey plots established in temperate montane forests located in Wolong Nature Reserve, Sichuan Province, China. As such, the procedure is useful for capturing changes in biodiversity induced by disturbances operating at large spatial scales and constitutes a suitable tool for monitoring and managing biodiversity.     

Isolation and characterization of Zymomonas mobilis mutants resistant to octadecyltrimethylammonium chloride,a detergent acting on hopanoid-producing bacteria

Growth of the hopanoid-producing bacterium Zymomonas mobilis was inhibited at low concentrations of the cationic detergent octadecyltrimethylammoniumchloride (OTAC). A relationship between sensitivity of Zymomonas mobilis to OTAC, presence of hopanoids and ethanol tolerance was postulated. Mutants resistant to OTAC were isolated from strains ZM1 and ZM4. They did not present any alteration of the hopanoid content and their squalene cyclases showed the same sensitity to OTAC as the parent enzymes. Resistance to OTAC paralleled pleiotropic effects including, enhanced accessibility of the membrane-bound alkaline phosphatase, important release of proteins from cells by Tris/HCl treatment, increased resistance to antibiotics and increased sensitivity to ethanol. In addition, OTAC^R mutants were also characterized by the synthesis or the overproduction of an outer membrane protein (F53) not detected on 2D-PAGE maps of parent strains and by a normal heat shock response. The role of hopanoids, heat shock proteins, protein F53 and membrane organization in ethanol tolerance is discussed.Abbreviations OTAC octadecyltrimethylammoniumchloride - SLS sodium lauryl sarcosinate     

Construction of Partially Balanced Incomplete Block Designs with Nested Rows and Columns

A number of methods of construction of partially balanced incomplete block designs with nested rows and columns are developed and new balanced incomplete block designs with nested rows and columns are obtained as a by-product.     

Cultivar-related differences in the distribution of cell-wall-bound thionins in compatible and incompatible interactions between barley and powdery mildew

Leaf-specific thionins of barley (Hordeum vulgare L.) have been identified as a novel class of cell-wall proteins toxic to plant-pathogenic fungi and possibly involved in the defence mechanism of plants. The distribution of these polypeptides has been studied in the host-pathogen system of barley and Erisyphe graminis DC.f.sp. hordei Marchal (powdery mildew). Immunogold-labelling of thionins in several barley cultivars indicates that resistance or susceptibility may be attributed to the presence or absence of thionins at the penetration site in walls and papillae of epidermal leaf cells.All of the leaf-specific thionin genes are confined to the distal end of the short arm of chromosome 6 of barley. None of the genes for cultivarspecific resistance to powdery mildew which have previously been mapped on barley chromosomes are found close to this locus.     

Regeneration of plants from hypocotyl protoplasts of rapessed (Brassica napus L. var. oleifera) cultivars

Protoplast cultures were prepared from hypocotyls of ten spring rapeseed cultivars. Protoplasts from all genotypes tested formed calli, and shoots were regenerated from calli of nine of the genotypes at frequencies varying from 15 to 76%. The regenerating cultivars fell into a high regenerating group (>60% and a low regenerating group <25%).     

Effect of salinity on phosphate accumulation and injury in soybean

Many soybean [Glycine max (L.) Merr.] genotypes that are grown in solution cultures are highly sensitive to the combination of both salinity and inorganic phosphate (Pi) in the substrate. This effect has been observed on numerous occasions on plants grown in a saline medium that contained a substantial amount of Ca (i.e., CaCl₂/NaCl=0.5 on a molar basis). Because Ca is important in regulating ion transport and membrane permeability, solution culture experiments were designed to examine the effects of various concentrations of Pi and ratios of CaCl₂/NaCl (0 to 0.5 on a molar basis) at a constant osmotic potential (−0.34 MPa) on this adverse interaction. Four soybean cultivars (‘Lee’, ‘Lee 74’ ‘Clark’ and ‘Clark 63’) were tested. No adverse salinity x Pi interaction was found on Lee at any ratio and leaf P and Cl were maintained below 300 and 200 mmol kg⁻¹ dry wt, respectively. Clark, Clark 63 and Lee 74 soybean plants, on the other hand, were severely injured by solution salinity (−0.34 MPa osmotic potential) when substrate Pi was ≥0.12 mM. Reduced substrate Ca did not intensify the salinity x Pi interaction. On the contrary, the onset of injury was hastened and more severe with increased CaCl₂/NaCl ratios in isotonic solutions. Shoot and root growth rates decreased as injury increased. Leaf P concentrations from these cultivars grown in saline solutions with 0.12 mM Pi were excessive (>600 mmol kg⁻¹ dry wt) compared with concentrations commonly found in soybean leaf tissue yet they were independent of the severity of injury. Since leaf Cl increased wiht increased CaCl₂/NaCl ratio, we suspect that the severity of foliar injury was related to the combined effects of excessive P and Cl within the tissue. Lee 74, the only injured cultivar examined that excluded Cl from its leaves, was less sensitive than either Clark cultivar and its injury was characteristically different. Other ion interactions were reported that may have played a role in injury susceptibility.     

Effect of Rhizobium andAzospirillum lipoferum inoculation on the nodulation,yield and nitrogen uptake of peanut cultivars

Peanut (Arachis hypogaea Linn.) Cvs. Robut 33-1 and JL 24 were inoculated with Rhizobium strain NC 92 and a strain ofAzospirillum lipoferum singly and as mixed inoculum. Seed inoculation with these bacteria enhanced nodulation, N content and yield of these cultivars under field conditions. While a mix inoculation of these two diazotrophic cultures had an adverse effect on these parameters as compare to single inoculation.     

N2 fixation by soybean-Bradyrhizobium combinations under acidity,low P and high Al stresses

Five strains of Bradyrhizobium japonicum (USDA 6, 110, 122, 138, and 143) were screened in cell culture for tolerance to acidity (pH 4.2, 4.4, and 4.6) and Al (0, 3, 4, 5, and 6 mg L^–1) under low P conditions. Each strain was later grown in association with seven soybean [Glycine max. (L) Merr.] cultivars which were also screened for tolerance to the same stresses in nutrient culture to determine which soybean-Bradyrhizobium combinations would establish the most effective symbiotic N₂ fixing relationships. Results indicated that strains USDA 110 and 6 were more tolerant than USDA 122, 138 and 143 with USDA 110 being the most tolerant. Acidity appeared to be the more severe stress; but even when strains showed tolerance to the stresses, cell numbers were significantly reduced. This suggests that colonization of soils and soybean roots can be adversely affected under similar conditions in the field which may result in reduced nodulation. The strains found to be more tolerant to the stresses were more effective N₂ fixers in symbiosis with all soybean cultivars, with USDA 110 being definitely superior. The association between the more tolerant strains and cultivars had the largest nitrogenase activity. Further studies on the inclusion of tolerant Bradyrhizobium strains in inoculum used on tolerant soybean cultivars in the field are warranted.     

Induced reversion of a Chinese hamster ovary triple auxotroph. Validation of the system with several mutagens

A Chinese hamster ovary triple auxotroph (CHO AUXB1) requires glycine, adenosine, and thymidine (GAT) for growth and survival due to a defect in the structural gene for folylpolyglutamate synthetase (FPGS). This auxotroph and others like it contain less than 3% of the parental amounts of FPGS activity. In order to develop a reverse mutation assay with CHO AUXB1, we determined the optimal conditions for measuring reversion and characterized some of the revertants. We also obtained quantitative mutagenicity data for several direct-acting mutagens for comparison to the parental CHO-S/HGPRT locus. Induced revertants appear in the culture immediately following 20-22 h exposures in +GAT complete medium, indicative of dominant genetic changes. They are maximally expressed after 2 population doublings and can be conveniently selected after 44-48 h of expression growth by plating 1 X 10(6) cells/100-mm dish into -GAT-deficient medium and incubating 12-13 days. Plating reconstruction experiments show that the cloning efficiencies of revertants in -GAT medium are not influenced by the presence of up to 1 X 10(6) CHO AUXB1 cells. Dose-dependent increases above the spontaneous revertant frequency (average = 5 X 10(7)) are induced with cis-Pt(NH3)2Cl2 (14-fold) (but not trans-Pt(NH3)2Cl2), PtCl4(10-fold), Pt(SO4)2 (14-fold), K2CrO4 (8-fold), EMS (10-fold), 4-NQO (53-fold), ICR-191 (60-fold), and ICR-170 (30-fold). All of the revertants that have been isolated are stable to repeated subculturing in -GAT medium; 40 out of 42 that have been analyzed are characterized by an increased 72-h growth incorporation of labeled folate and their extracts contain 5-94% as much FPGS as the original, parental CHO-S line. Spontaneous and induced reversion to the GAT+ phenotype primarily reflects mutations involving the FPGS gene locus. But the re-acquisition by most of the revertants of much less than normal amounts of FPGS activity suggests that they arise from compensatory second-site mutations within this gene. Comparison of the mutagenicity patterns of the foregoing compounds as a function of the applied concentration and the relative percent survival reveals some interesting similarities, as well as differences, between the CHO AUXB1/FPGS and CHO-S/HGPRT loci. In particular, the FPGS locus is rather insensitive to EMS (or other simple alkylating agents). However, it seems to be quite susceptible to reversion by other chemicals that are known to react selectively with guanine bases in DNA. CHO AUXBI is a useful supplemental mammalian assay system for assessing quantitatively the generally weak mutagenic activities of metal compounds.