Ajay Krishna Saha

Plant Water-Stress Response Mechanisms

Water, the central molecule of life, plays a profound role in a number of plant life processes ranging from photosynthesis to macromolecular interaction through hydrophobic bond. Due to imbalances in natural status of the different physiological, environmental conditions and during natural calamities, plants are exposed to either deficit of water (i.e. drought) or excess of water (i.e. flooding). Both of these conditions lead to water stress on plants which in turn results in disruption of agriculture and food supply in different parts of the world. In this chapter, a brief idea on the causes, indicators, responses and adaptation processes to the water stress in plants and the associated molecular mechanisms has been presented. In this chapter, the stresses related to water are expressed as “drought”. The cellular and molecular responses of plants to water stress have been studied intensively throughout the world. Understanding the mechanisms by which plants perceive water stress and transmit the subsequent signals to cellular machinery and modulate expression of genes and their products to activate adaptive responses is of fundamental importance to plant biology. Knowledge about water-stress signal transduction is therefore vital for continued development of rational breeding and transgenic strategies to improve stress tolerance in crops. Factors controlling water-stress conditions alter the normal equilibrium and lead to a series of morphological, physiological, biochemical and molecular changes in plants which adversely affect their growth and productivity. However, plants also have developed innate adaptations to water-stress conditions with an array of biochemical and physiological interventions that involve the function of many stress-associated genes. Water-stress-associated hormones like ABA are found to play a central role in orchestrating the molecular and physiological responses leading protective responses in plants. Overall, this chapter provides a systemic glimpse of integrated cellular and whole plant responses to water stress.

Molecular Characterization and Antioxidant Potential of Three Wild Culinary-Medicinal Mushrooms from Tripura, Northeast India

The aim of this study was to characterize 3 wild culinary-medicinal mushrooms using molecular tools and to analyze their antioxidant activity. Antioxidant properties were studied by evaluating free radical scavenging, reducing power, and chelating effect. The mushrooms were identified as Lentinus squarrosulus, L. tuber-regium, and Macrocybe gigantean by amplifying internal transcribed spacer regions of ribosomal DNA. The results demonstrated that the methanolic extract of M. gigantean has the highest free radical scavenging effect and chelating effect, whereas the methanolic extract of L. squarrosulus has the highest reducing power. The highest total phenol content and the most ascorbic acid were found in the M. gigantean extracts. Among the 3 mushroom extracts, M. gigantean displayed the most potent antioxidant activity. Molecular characterization using the nuclear ribosomal internal transcribed spacer region as a universal DNA marker was an effective tool in the identification and phylogenetic analysis of the studied mushrooms. The study also indicated that these wild macrofungi are rich sources of natural antioxidants.

ALLELOPATHIC EFFECT OF CLERODENDRUM INFORTUNATUM L. LEAF EXTRACT ON SEED GERMINATION AND SEEDLING GROWTH OF SOME AGRICULTURAL CROPS OF TRIPURA, INDIA

This study was aimed to evaluate the allelopathic effect of the aqueous leaf extract of Clerodendrum infortunatum L. on seed germination, plumule and radicle growth of some agricultural crops such as Triticum aestivum L. (Wheat), Brassica campestris (Mustard), Vigna radiata (L) R.wilczek (Mung bean) and Trigonella foenum-graecum L. (Methi). The ground leaves of C. infortunatum were mixed with distilled water in 1:10 ratio and used as stock solution. The inhibitory effect was studied at 25%, 50% and 75% of aqueous solution and distilled water (control). It was found that the aqueous leaf extract C. infortunatum had inhibitory effect on germination, plumule and radical elongation of tested crops. The results revealed that the inhibitory effect was much more pronounced at higher extract concentrations showing allelopathic potential which may be exploited in controlling seed germination and seedling growth of crops.

New Distribution Record of Five Species of Xylaria from Tripura, Northeast India

Abstract This retrospective study analyses sex differences in foetal biometry from the 1st trimester onwards, and sexual dimorphism in newborn size of 4260 singleton term births taking place at the Viennese Danube hospital between 2005 and 2013. Crown-rump length was determined at the 11th to 12th week, biparietal diameter, fronto-occipital diameter, head circumference, abdominal transverse diameter, abdominal anterior-posterior diameter, abdominal circumference and femur length were determined at the 20th or 21st gestational week and at the 32nd or 33rd week of gestation. Immediately after birth, birthweight, birth length and head circumference were taken, the Apgar scores 1, 5 and 10 minutes after birth were determined. Significant sex differences were found from the first trimester onwards. With exception of femur length, male foetuses exhibited always the significantly larger dimensions. At the time of birth, male newborns were significantly larger and heavier than their female counterparts. Sex had an independent impact on foetal biometry and newborn size.