Effects of Metabolic Inhibitors on the Calcification of a Freshwater Green Alga Gloeotaenium loitlesbergarianum Hansgirg. 2. Effects of Some Inhibitors of Protein Synthesis

The effects of five inhibitors of protein synthesis, viz. streptomycin,aurin tricarboxylic acid, tetracycline, chloramphenicol, andcycloheximide, on the calcification of Gloeotaenium loitlesbergarianumHansgirg, a freshwater green alga were studied. Streptomycinhad no effect while aurin tricarboxylic acid at 50 µgml^–1 and tetracyline, chloramphenicol and cycloheximideat 20 µg ml^–1 completely inhibited calcificationin the alga. High concentrations of chloramphenicol and cycloheximidewere not completely inhibitory when added 26 h and 32 h respectivelyafter the material was incubated in the induction medium. Itis concluded that the effects by these substrates are the resultsof inhibition of protein synthesis, which is directly or indirectlylinked to calcification. calcification, Gloeotaenium loitlesbergarianum Hansgirg, green alga, chlorophyceae, protein synthesis inhibitors     

Gravistimulus Direction, Ethylene Production and Shoot Elongation in the Release of Apical Dominance in Pharbitis nil

Prasad, T. K. and Cline, M. G. 1985. Gravistimulus direction,ethylene production and shoot elongation in the release of apicaldominance in Pharbitis nil.—. exp. Bot. 36: 1969–1975.Release of apical dominance can be induced in Pharbitis nilby the inversion of the upper shoot. This promotion of outgrowthof the highest lateral bud adjacent to the bend of the stemappears to be mediated by ethylene inhibition of growth of theinverted main shoot. In the present investigation the existenceof a direct correlation between ethylene evolution and the directionof gravistimulus is demonstrated as well as an inverse correlationbetween ethylene production by the inverted upper shoot andits elongation. An inverse correlation also exists between elongationof the inverted upper shoot and the outgrowth of the highestlateral bud if the lower portion of the shoot (below the bend)is oriented in an upright position. The latent period for shoot–inversioninduction of ethylene production is about 2 h. These resultssupport the hypothesis of indirect ethylene control of apicaldominance release by retardation of elongation of the invertedshoot. Key words: Shoot inversion, gravistimulus, ethylene, latent period, bud outgrowth, pharbitis nil     

Variability and divergence in Pongamia pinnata (L.) Pierre germplasm – a candidate tree for biodiesel

Three explorations were undertaken in South East Coastal zone of India covering parts of Andhra Pradesh (AP) and Orissa states to collect Pongamia pinnata (L.) Pierre germplasm during March–June 2007. A total of 123 accessions were collected and seed data recorded were analyzed for morphometric traits viz., seed length, seed width, seed thickness, 100‐seed weight and oil content. Variation in the collected germplasm was analyzed using anova , simple measures of variation and D² statistics. Significant genetic variability between seed traits and oil content and association among the seed traits was recorded. Phenotypic variance was higher than genotypic variance for all the characters indicating dominant role of environment. High heritability (broad sense) for 100‐seed weight (97.6%) and oil content (86.7%) indicated the reliability of these characters as selection criteria for plus trees. Genetic gain was maximum for 100‐seed weight (62.6%) followed by oil content (30.5%). D² analysis grouped the accessions into 12 clusters. Cluster XII and cluster IX were the most diverse based on the intercluster distance. Based on the observed diversity, Chittoor, Srikakulam and Adilabad districts of AP are most suitable for collecting diverse germplasm lines and also for in situ conservation.     

Nitrogen deposition in tropical forests from savanna and deforestation fires

We used satellite‐derived estimates of global fire emissions and a chemical transport model to estimate atmospheric nitrogen (N) fluxes from savanna and deforestation fires in tropical ecosystems. N emissions and reactive N deposition led to a net transport of N equatorward, from savannas and areas undergoing deforestation to tropical forests. Deposition of fire‐emitted N in savannas was only 26% of emissions – indicating a net export from this biome. On average, net N loss from fires (the sum of emissions and deposition) was equivalent to approximately 22% of biological N fixation (BNF) in savannas (4.0 kg N ha^?1 yr^?1) and 38% of BNF in ecosystems at the deforestation frontier (9.3 kg N ha^?1 yr^?1). Net N gains from fires occurred in interior tropical forests at a rate equivalent to 3% of their BNF (0.8 kg N ha^?1 yr^?1). This percentage was highest for African tropical forests in the Congo Basin (15%; 3.4 kg N ha^?1 yr^?1) owing to equatorward transport from frequently burning savannas north and south of the basin. These results provide evidence for cross‐biome atmospheric fluxes of N that may help to sustain productivity in some tropical forest ecosystems on millennial timescales. Anthropogenic fires associated with slash and burn agriculture and deforestation in the southern part of the Amazon Basin and across Southeast Asia have substantially increased N deposition in these regions in recent decades and may contribute to increased rates of carbon accumulation in secondary forests and other N‐limited ecosystems.     

Mating with large males decreases the immune defence of females in Drosophila melanogaster

Mating has been widely reported to be a costly event for females. Studies indicate that female cost of mating in terms of fecundity and survivorship can be affected by their mates, leading to antagonistic coevolution between the sexes. However, as of now, there is no evidence that the female cost of mating in terms of immune defence is affected by their mates. We assess the effect of different sized males on antibacterial immune defence and reproductive fitness of their mates. We used a large outbred population of Drososphila melanogaster as the host and Serratia marcescens as the pathogen. We generated three different male phenotypes: small, medium and large, by manipulating larval densities. Compared to females mating with small males, those mating with large males had higher bacterial loads and lower fecundity. There was no significant effect of male phenotype on the fraction of females mated or copulation duration (an indicator of ejaculate investment). Thus, our study is the first clear demonstration that male phenotype can affect the cost of mating to females in terms of their antibacterial immune defence. Mating with large males imposes an additional cost of mating to females in terms of reduced immune defence. The observed results are very likely due to qualitative/quantitative differences in the ejaculates of the three different types of males. If the phenotypic variation that we observed in males in our study is mirrored by genetic variation, then, it can potentially lead to antagonistic coevolution of the sexes over immune defence.     

Male-limited evolution suggests no extant intralocus sexual conflict over the sexually dimorphic cuticular hydrocarbons of <Emphasis Type="Italic">Drosophila melanogaster</Emphasis>

Sexually dimorphic traits are likely to have evolved through sexually antagonistic selection. However, recent empirical data suggest that intralocus sexual conflict often persists, even when traits have diverged between males and females. This implies that evolved dimorphism is often incomplete in resolving intralocus conflict, providing a mechanism for the maintenance of genetic variance in fitness-related traits. We used experimental evolution in Drosophila melanogaster to directly test for ongoing conflict over a suite of sexually dimorphic cuticular hydrocarbons (CHCs) that are likely targets of sex-specific selection. Using a set of experimental populations in which the transmission of genetic material had been restricted to males for 82 generations, we show that CHCs did not evolve, providing experimental evidence for the absence of current intralocus sexual conflict over these traits. The absence of ongoing conflict could indicate that CHCs have never been the target of sexually antagonistic selection, although this would require the existing dimorphism to have evolved via completely sexlinked mutations or as a result of former, but now absent, pleiotropic effects of the underlying loci on another trait under sexually antagonistic selection. An alternative interpretation, and which we believe to be more likely, is that the extensive CHC sexual dimorphism is the result of past intralocus sexual conflict that has been fully resolved, implying that these traits have evolved genetic independence between the sexes and that genetic variation in them is therefore maintained by alternative mechanisms. This latter interpretation is consistent with the known roles of CHCs in sexual communication in this species and with previous studies suggesting the genetic independence of CHCs between males and females. Nevertheless, direct estimates of sexually antagonistic selection will be important to fully resolve these alternatives.     

Further evidence for the genetic basis of qualitative traits and their linkage relationships in dolichos bean (<Emphasis Type="Italic">Lablab purpureus</Emphasis> L.)

An investigation on inheritance of qualitative traits in dolichos bean revealed biallelic monogenic control of photoperiod-induced sensitivity to flowering time and flower colour in F ₂ and F ₃ generations. While, growth habit and pod curvature are each controlled by two genes that exhibit classical complementary epistasis, raceme emergence was controlled by two genes that displayed classical inhibitory epistasis. The dominant alleles, at two different unlinked pairs of genes are necessary for plants to exhibit indeterminate growth habit and bear straight pods. Any other combination of alleles at the two pairs of genes result in plants displaying determinate growth habit and bearing curved pods. While, the genes controlling growth habit, PSFT and raceme emergence are linked. Those controlling flower colour and pod curvature are segregated independent of each other. These results are discussed in relation to strategies for breeding dolichos bean.     

Studies in the Physiological Action of 2,2-Dichloropropionic Acid: II. THE EFFECTS OF LIGHT AND TEMPERATURE ON THE FACTORS RESPONSIBLE FOR THE INHIBITION OF GROWTH

When Lemna minor and Salvinia natans, grown in a constant environment,are subjected to sub-lethal concentrations of 2,2-dichioropropionicacid (DCPA), the relative growth-rates are progressively reduced.These cumulative reductions, which are greater for S. natans,are correlated with decreases in (1) the rate of leaf or frondformation, (2) the mean area per leaf or frond, and (3) thenet assimilation rate. Of these components, the first is themost important and the third is the least. The effects of light intensity (300, 600, 900 f.c.), temperature(20, 25, and 30°C), and concentration of DCPA on both therelative growth-rate and rate of leaf or frond multiplicationhave been examined in multi-factorial experiments. Over theconcentration range selected (100, 200, and 400 mg/l for S.natans and 100, 300, and 6oo mg/l for L. minor) there are positiveeffects of light intensity, temperature, and concentration.For each concentration the order of the depression is maximalunder a combination of the highest temperature and the greatestintensity. Using radioactive DCPA it has been established that uptake isalso a cumulative process, and that S. natans has a greatercapacity to absorb DCPA. The rate of uptake is independent ofthe light intensity but increases with temperature and concentration. DCPA brings about morphological and structural changes. In S.natans, many of the leaves become submerged and the proportionis positively dependent on light, temperature, and concentration.This failure to float is associated with a reduction in thedensity of epiderrnal hairs. It is concluded that the inhibitory effects of DCPA are maximalunder conditions which are optimal for both meristematic activityand accumulation.