Pectin esterase in relation to leaf abscission in coleus and phaseolus

Pectin esterase (PE) activities in abscission zones, other portions of leaves, and adjacent stem tissues were compared in attached leaves and abscissing petioles (previously debladed) of Coleus blumei Benth. and Phaseolus vulgaris L., cv. Canadian Wonder. Earlier findings of Osborne in bean were confirmed and changes in PE activity in coleus were shown to resemble those in bean in some respects. In both plants PE was lower in the distal portion of abscission zones of abscissing petioles than in that portion of attached leaves but this difference was not as large or as consistently clear-cut in coleus as in bean. The general level of PE activity was an order of magnitude lower and changes associated with abscission were smaller in coleus than in bean. Auxin treatment of debladed petioles of coleus prevented abscission and resulted in small increases in PE activity in abscission zones and most of the other regions sampled. The largest increase was observed in the stem tissue adjacent to the attached leaf opposite the debladed, auxin treated one.     

The effect of porcine calcitonin on plasma calcium in Channa punctatm Bloch

The effect of porcine calcitonin on the plasma calcium of the freshwater Indian murrel, Channa punctatus Bloch has been studied. An injection of 200 MRC mU of porcine calcitonin was given intraperitoneally, while control fish received the gelatin carrier. A significant hypocalcaemia was noted I h after calcitonin treatment (P < 0.001). The plasma calcium had returned to the normal level by the 6th h.     

Studies of soil moisture stress in barley (Hordeum vulgare L.)

Summary The objective was to find the optimum range of water contents for inducing better growth, physiological efficiency and yield potential of barley plants (Hordeum vulgare L. var. K18). A pot culture experiment was conducted in the Division of Crop Physiology and Biochemistry Kanpur-2. The plants were subjected to various soil moisture stresses,i.e., 0.15, 0.30, 0.45, 0.60 and 0.75 atm tension throughout the crop growth period measured by irrometers.Plants maintained at 0.45 soil moisture tension required 19.07 litre of water and had the best water use efficiency (1765 mg dm/litre of water) which favourably influenced the leaf water balance (85.9%), plant growth as measured by plant height (85.4 cm) and tiller production (35.6) per hill, photosynthetic efficiency (2.185 mg CO₂/g dm/h), grain number (722) and grain yield (33.7 g) per hill while plants irrigated at a tension greater than 0.45 SMT did not develop as well. However, protein and gluten percentage increased gradually with the subsequent increase in soil moisture tension. On the other hand respiration rate (2.090 mg CO₂/g dm/hr) and leaf area (4375 cm²) were recorded to be the highest at 0.60 and 0.30 atm SMT respectively.Thus it is suggested that for reaping high harvest of barley crop, the physiological need of water (19.07 litre) in total of plant life should be made available through scheduled irrigation based on maintenance of plant at 0.45 SMT from seeding to maturity.     

The actin cytoskeleton is required to elaborate and maintain spatial patterning during trichome cell morphogenesis in Arabidopsis thaliana

Arabidopsis thaliana trichomes provide an attractive model system to dissect molecular processes involved in the generation of shape and form in single cell morphogenesis in plants. We have used transgenic Arabidopsis plants carrying a GFP-talin chimeric gene to analyze the role of the actin cytoskeleton in trichome cell morphogenesis. We found that during trichome cell development the actin microfilaments assumed an increasing degree of complexity from fine filaments to thick, longitudinally stretched cables. Disruption of the F-actin cytoskeleton by actin antagonists produced distorted but branched trichomes which phenocopied trichomes of mutants belonging to the 'distorted' class. Subsequent analysis of the actin cytoskeleton in trichomes of the distorted mutants, alien, crooked, distorted1, gnarled, klunker and wurm uncovered actin organization defects in each case. Treatments of wild-type seedlings with microtubule-interacting drugs elicited a radically different trichome phenotype characterized by isotropic growth and a severe inhibition of branch formation; these trichomes did not show defects in actin cytoskeleton organization. A normal actin cytoskeleton was also observed in trichomes of the zwichel mutant which have reduced branching. ZWICHEL, which was previously shown to encode a kinesin-like protein is thought to be involved in microtubule-linked processes. Based on our results we propose that microtubules establish the spatial patterning of trichome branches whilst actin microfilaments elaborate and maintain the overall trichome pattern during development.     

Identification of an intracellular pyrimidine-specific endoribonuclease from Bacillus subtilis.

Two intracellular RNases which were easily separated by fractionation on strong anion- or cation-exchange resins were identified from Bacillus subtilis. One cleaved any phosphodiester bond, while the second cleaved only pyrimidine-N bonds. The enzyme with pyrimidine-N specificity was approximately 15 kDa, had a pH optimum of approximately 6.2, degraded C-C bonds approximately 10 times faster than U-U bonds, and was completely inactive against single-stranded DNA. The enzyme is called RNase C and may be the first reported broad-specificity endoribonuclease from B. subtilis.     

Cluster analysis of genes for nitrogen fixation from several diazotrophs

Hierarchical clustering and similarity coefficients of pairwise alignments of the published nucleotide sequences of 27nifH genes suggest thatnif genes are as ancient as the archaebacteria and clostridia. The positions ofnifHl ofMethanococcus thermolithotrophicus, nifH3 ofClostridium pasteurianum, nifH3 ofAzotobacter vinelandii andnifH ofFrankia suggest that a variety of lateral transfers may have occurred during evolution ofnifH gene. The genes for type 3 nitrogenase ofA. vinelandii may have diverged early from methanogens and clostridia. A high similarity coefficient with the derived amino acid sequence of type 3 nitrogenase suggests the presence of a functionally similar enzyme inC. pasteurianum. The type 2 nitrogenase genenifH2 of azotobacters seems to have originated recently from the genenifHl for conventional type I nitrogenase. RhizobialnifH genes comprise two closely related but discrete clusters that are in consonance with the plasmid or chromosomal location ofnif genes. The chromosomal and plasmid locatednifH of rhizobia seem to have evolved independently but contemporaneously.