Effect of Water Deficit Stress on Diffusive Resistance, Transpiration, and Spikelet Desiccation of Rice (Oryza sativa L.)

To understand the nature of panicle resistance to water loss,diffusive resistance, transpiration rate, and degree of tissuedesiccation were studied as affected by low tissue water potentialsand relative water contents (RWC) induced by water deficit stresses.A drought susceptible cultivar (IR20) and a moderately resistantcultivar (IRAT 13) were compared under moderate and severe waterdeficit stresses under greenhouse conditions. Irrigation waswithdrawn at flowering stage. During the 10-d stress period,changes in panicle and flag leaf transpiration and white headformation (desiccated) were monitored. Using cut panicles transpirationand white head formation at different RWC levels in 11 differentcultivars were also measured. In flag leaves, increased diffusiveresistance and leaf rolling reduced transpirational losses fromthe adaxial surfaces. Leaf resistance and rolling were linearlycorrelated with leaf water potentials. Resistance in paniclesincreased with progress decline in water potentials, but thechange was not as high as in leaves. Among test cultivars, diffusive resistance increased at thelate flowering stage but not at the early stage when panicleswere newly emerged. Increased water losses contributed to severespikelet desiccation and white heads. A few of the upland cultivarstested, such as Kinandang Patong, IRAT 140 and IRAT 13 conservedmore water and showed reduced water-deficit stress symptoms.Copyright1993, 1999 Academic Press Drought tolerance, drought susceptibility, rice panicles     

DYNAMIN-RELATED PROTEIN DRP1A functions with DRP2B in plant growth,flg22-immune responses,and endocytosis

Ligand-induced endocytosis of the immune receptor FLAGELLIN SENSING2 (FLS2) is critical for maintaining its proper abundance in the plasma membrane (PM) to initiate and subsequently down regulate cellular immune responses to bacterial flagellin or flg22-peptide. The molecular components governing PM abundance of FLS2, however, remain mostly unknown. Here, we identified Arabidopsis (Arabidopsis thaliana) DYNAMIN-RELATED PROTEIN1A (DRP1A), a member of a plant-specific family of large dynamin GTPases, as a critical contributor to ligand-induced endocytosis of FLS2 and its physiological roles in flg22-signaling and immunity against Pseudomonas syringae pv. tomato DC3000 bacteria in leaves. Notably, drp1a single mutants displayed similar flg22-defects as those previously reported for mutants in another dynamin-related protein, DRP2B, that was previously shown to colocalize with DRP1A. Our study also uncovered synergistic roles of DRP1A and DRP2B in plant growth and development as drp1a drp2b double mutants exhibited severely stunted roots and cotyledons, as well as defective cell shape, cytokinesis, and seedling lethality. Furthermore, drp1a drp2b double mutants hyperaccumulated FLS2 in the PM prior to flg22-treatment and exhibited a block in ligand-induced endocytosis of FLS2, indicating combinatorial roles for DRP1A and DRP1B in governing PM abundance of FLS2. However, the increased steady-state PM accumulation of FLS2 in drp1a drp2b double mutants did not result in increased flg22 responses. We propose that DRP1A and DRP2B are important for the regulation of PM-associated levels of FLS2 necessary to attain signaling competency to initiate distinct flg22 responses, potentially through modulating the lipid environment in defined PM domains.

A plant-specific large dynamin GTPase is required for plant responses against bacterial pathogens and, with another dynamin, regulates the cell surface composition for plant growth and defense.     

“We lost all we had in a second”: coping with grief and loss after a natural disaster

Natural disasters cause immense suffering among affected communities. Most occur in developing countries, which have fewer resources to respond to the resulting traumas and difficulties. As a consequence, most survivors have to rely on their own coping resources and draw from what support remains within family, social networks and the wider community to manage and deal with their losses and consequent emotional distress. Taking the 2004 Asian tsunami as an example, this article reports findings from a qualitative study designed to investigate how survivors responded in Sri Lanka, and the range of coping strategies adopted and resources mobilized. In‐depth interviews were conducted with 38 survivors purposively sampled from the Matara district of southern Sri Lanka. Survivors' accounts emphasized the importance of extended supportive networks, religious faith and practices, and cultural traditions in facilitating recovery and sustaining emotional well‐being. Government and external aid responses that promoted these, through contributing to the re‐establishment of social, cultural, and economic life, were particularly valued by participants. Recourse to professional mental health care and Western psychological interventions was limited and survivors preferred to seek help from traditional and religious healers. Our findings tentatively suggest that long‐term mental health following disaster may, in the first instance, be promoted by supporting the re‐establishment of those naturally occurring resources through which communities traditionally respond to suffering.     

Ultrastructure of the osteogenesis of acellular vertebral bone in the Japanese medaka, Oryzias latipes (Teleostei, Cyprinidontidae)

An ultrastructural study by transmission electron microscopy (TEM) of the vertebrae of embryonic, larval, juvenile and mature medaka shows that each vertebra consists of a core of notochordal cells surrounded by a sheath of bone. The vertebral bone lacks either fully or partially embedded cells in the matrix throughout development. Bone matrix is secreted by a layer of cells that lies over the outer surface of the vertebral bone. During the early stages of osteogenesis, these cells secrete bone matrix all around themselves. However, because of the gradual flow of the newly synthesized bone matrix through intercellular spaces, matrix-producing cells do not become trapped in their own secretion. In later stages of osteogenesis, these cells secrete matrix only toward the already-deposited bone. This polarized matrix secretion allows the osteoblasts to stay always on the bone surface and never to become trapped in the matrix as osteocytes.