The Effect of EGTA, Calcium Channel Blockers (Lanthanum Chloride and Nifedipine) and their Interaction with Abscisic Acid on Seed Germination of Brassica juncea cv. RLM-198

Recent investigations have shown that abscisic acid (ABA) dependsupon the availability of Ca²⁺ for its action in certain systems.In order to check whether ABA requires Ca²⁺ to inhibit seedgermination, the effects of ABA, CaCl₂, EGTA (a Ca²⁺ chelator)and lanthanum chloride and nifedipine (Ca²⁺ channel blockers),individually and in combination, on seed germination of Brassicajuncea L. cv. RLM-198 were studied. ABA inhibited germinationin a concentration dependent manner. ABA-induced inhibitionwas abolished with the lapse of time after application. Calciumneither affected germination nor altered the ABA-induced inhibition.EGTA. La³⁺ and nifedipine suppressed seed germination when testedindividually and further elevated the ABA effect, in a synergisticway, when applied simultaneously. They also prevented the time-dependentreduction in ABA-induced inhibition. The findings indicate thatCa²⁺ is not essential for ABA to cause germination inhibition. EGTA, Ca²⁺ channel blockers, abscisic acid, seed germination, Brassica juncea     

Genetic diversity studies and identification of SSR markers associated with Fusarium wilt (Fusarium udum) resistance in cultivated pigeonpea (Cajanus cajan)

Genetic diversity and identification of simple sequence repeat markers correlated with Fusarium wilt resistance was performed in a set of 36 elite cultivated pigeonpea genotypes differing in levels of resistance to Fusarium wilt. Twenty-four polymorphic sequence repeat markers were screened across these genotypes, and amplified a total of 59 alleles with an average high polymorphic information content value of 0.52. Cluster analysis, done by UPGMA and PCA, grouped the 36 pigeonpea genotypes into two main clusters according to their Fusarium wilt reaction. Based on the Kruskal–Wallis ANOVA and simple regression analysis, six simple sequence repeat markers were found to be significantly associated with Fusarium wilt resistance. The phenotypic variation explained by these markers ranged from 23.7 to 56.4%. The present study helps in finding out feasibility of prescreened SSR markers to be used in genetic diversity analysis and their potential association with disease resistance.     

A Household Perspective for Biodiversity Conservation

Abstract: Many researchers have implicated human population density in species endangerment, but these correlative studies do not demonstrate causality. We propose that hypotheses implicating human population density in wildlife endangerment at global and national scales owe their public and academic currency as thoroughly to inductive reasoning and repetition as to scientific experimentation. It follows that alternative research hypotheses generated from the same facts should provide equally tenable results. Household density provides such an alternative hypothesis and is growing faster than human population density. We used linear multiple regression models to demonstrate that household density provides a viable alternative statistical hypothesis to human population density for explaining species endangerment (household model, r² = 0.85; population model, r² = 0.84). We then suggest adopting a household perspective for biodiversity conservation because 1) social norms and practices render a household approach to conservation more pragmatic than a human population perspective and 2) shifting the focus toward households could facilitate movement from a human-versus-nature ethic to a humans-situated-within-nature ethic (e.g., a land ethic). Wildlife managers and researchers concerned about the negative influence humans have on biodiversity should consider grounding research, theory, and policy decisions in the dynamics of human households as an alternative to human population.     

PHYCOLOGY AND HEAVY-METAL POLLUTION

1. All heavy metals, including those that are essential micronutrients (e.g. copper, zinc, etc.), are toxic to algae at high concentrations. 2. One characteristic feature of heavy-metal toxicity is the poisoning and inactivation of enzyme systems. Many of the physiological and biochemical processes, viz., photosynthesis, respiration, protein synthesis and chlorophyll synthesis, etc., are severely affected at high metal concentrations. 3. Some algae inhabit waters chronically polluted with heavy-metal-laden wastes from mining and smelting operations; Nodularia sp., Oscillatoria sp., Cladophora sp., Hormidium sp., Fucus sp. and Laminaria sp., etc., occur in metal-rich waters. These algal forms are probably more capable of combating the toxic levels of heavy metals and this attribute is a result of physiological and/or genetic adaptations. The sensitivity or tolerance to heavy metals varies amongst different algae. The phenomena of multiple tolerance and co-tolerance may be exhibited by some algae. 4. Heavy-metal pollution causes reduction in species diversity leading to the dominance of a few tolerant algal forms. The primary productivity also decreases after metal supplementation. 5. The uptake and accumulation of heavy metals can be active (energy-dependent), passive (energy-independent), or both. 6. Heavy metals can be safely stored as intranuclear complexes by some algae. Notwithstanding this, some changes in the cell wall can enable the algae to tolerate heavy metals by checking the entry of the metals (exclusion mechanism). 7. The metal content of algae growing in a waterbody may yield valuable information for simulating heavy metal pollution: several species of Cladophora and Fucus have been extensively used for this purpose. 8. Several factors affect and determine toxicity of heavy metals to algae. At low pH, the availability of heavy metals to algae is greatly increased, as a consequence of which pronounced toxicity is evident. Hard waters decrease metal toxicity. Some ions, e.g., calcium, magnesium and phosphorus, can alleviate toxicity of metals. 9. The presence of other metals can influence toxicity of a heavy metal through simple additive effect or by synergistic and antagonistic interactions. Similarly, other pollutants can influence heavy-metal toxicity. 10. The toxicity of heavy metals depends upon their chemical speciation. Various ionic forms of a metal characterized by different valency states, may be differentially toxic to a test alga. 11. Amino acids, organic matter, humic acids, fulvic acid, EDTA, NTA, etc. can complex with heavy metals and render them unavailable. This may eventually lead to less toxicity. 12. Heavy-metal toxicity largely depends upon algal population density: the denser the population the more numerous the cellular sites available, leading to decreased toxicity.     

Effects of mammalian pituitary gonadotropins on the seasonally quiescent ovary of the Indian wall lizard, Hemidactylus flaviviridis

Adult Indian wall lizards, Hemidactylus flaviviridis (Rüppell) with seasonally quiescent ovaries were treated either with ovine FSH or LH. Quantitative as well as histochemical observations revealed that only FSH could stimulate the ovarian growth and steroidogenesis whereas LH had no effect either on ovarian growth or on ovarian steroidogenesis.     

Studies on the Physiology of Host-parasite Relationship in Orobanche. III. Carbohydrate and Nitrogen Metabolism of Host and Parasite

Determination of different carbohydrate and nitrogen fractions was made in tomato (Lycopersicum esculentum Mill.) and mustard (Brassica campestris L.) serving as hosts for Orobanche cernua and O. aegyptiaca respectively. Shoots of Orobanche were also subjected to such analyses. Infection raised the level of total reducing and total sugar in the host with a simultaneous decrease in the level of acid-hydrolyzable and total carbohydrates in the constituent organs of infected hosts. This has been explained to be due to predominance of hydrolytic activity in the infected host. Infection also brought about a depression in the proportion of sucrose to the pool of total sugar in the host. This was also possibly due to predominance of hydrolytic processes and retardation in the synthetic processes. Higher concentration of acid-hydrolyzable and total carbohydrates in Orobanche than in the host indicated a high demand for sugars by the parasite. The insignificant differences between the relative proportions of different nitrogen fractions to the pool of total nitrogen in healthy and infected hosts indicated that nitrogen metabolism was not deranged in any way due to infection. Orobanche always had a lower concentration of total soluble and total nitrogen than the host root.     

Interference of Ascorbic Acid with the Starch-lodine Reaction

Starch estimation in various plant tissues is accomplished usinga reaction between starch and iodine. We report that the starch-iodinereaction is strongly inhibited by ascorbic acid, a normal cellularconstituent of higher plants. The presence of 10^–4 M ascorbicacid in the reaction mixture caused an almost complete inhibitionof the starch-iodine reaction. This inhibition may be alleviatedby increasing the amounts of iodine-potassium iodide (IKI) inthe reaction mixture, suggesting the possibility that a complexis formed between ascorbic acid and iodine. Evidence for thiscomes from a shift in absorption maxima of ascorbic acid dueto addition of IKI. Starch-iodine reaction, ascorbic acid, interference