Sagar Jagtap

Effects of Hypergravity on the Chlorophyll Content and Growth of Root and Shoot During Development in Rice Plants

Earlier Studies On Hypergravity Effects Showed Modification In The Metabolism Of Cell Wall Components, Promotion Of Metaxylem Development And Decrease In Extensibility Of Secondary Cell Walls In Arabidopsis Thaliana (Tamaoki Et Al. 2006; Nakabayashi Et Al. 2006). In The Present Study, The Effects Of Hypergravity On Rice Seeds Which Were Exposed To Hypergravity Conditions And Grown Under Normal Gravity Have Been Studied. Rice Seeds (Prh-10 Obtained From National Seeds Corporation, Govt. Of India) Were Suspended In Water In A Test Tube And Were Exposed To Hypergravity Ranging From 500–3,000 G For 10 Min. Seeds Exposed To Hypergravity Were Grown On 0.8% Agar Under Ambient Conditions And Light Intensity Of 1,250 Lux For 16 H Per Day. Seeds Unexposed To Hypergravity Grown Under The Same Conditions Acted As Control. Length Of Roots And Shoots Were Measured. Chlorophyll Was Extracted On The Fifth Day And Absorption And Fluorescence Spectra Were Recorded In Both Control And Hypergravity Samples. The Cross Parts Of The Roots Were Obtained And Studied Under The Microscope. The Results Obtained Showed That The Chlorophyll Content Was Less In The Samples Exposed To Hypergravity. The Roots Showed Changes In The Diameter Of Cells At The Core. To The Best Of Our Knowledge, Such Type Of Study Has Been Reported For The First Time.

LIFE AND GRAVITY

All organisms on earth have evolved at unit gravity and thus are probably adapted to function optimally at 1 g. However, with the advent of space exploration, it has been shown that organisms are capable of surviving at much less than 1 g, as well as at greater than 1 g. Organisms subjected to increased g levels exhibit alterations in physiological processes that compensate for novel environmental stresses, such as increased weight and density-driven sedimentation. Weight drives many chemical, biological, and ecological processes on earth. Altering weight changes these processes. The most important physiological changes caused by microgravity include bone demineralization, skeletal muscle atrophy, vestibular problems causing space motion sickness, cardiovascular deconditioning, etc. Manned missions into space and significant concerns in developmental and evolutionary biology in zero and low gravity conditions demand a concentrated research effort in space-medicine, physiology and on a larger scale — gravitational biophysics. Space exploration is a new frontier with long-term missions to the moon and Mars not far away. Research in these areas would also provide us with fascinating insights into how gravity has shaped our evolution on this planet and how it still governs some of the basic life processes. Understanding the physiological changes caused by long-duration microgravity remains a daunting challenge. The present concise review deals with the effects of altered gravity on the biological processes at the cellular, organic and systemic level which will be helpful for the researchers aspiring to venture in this area. The effects observed in plants and animals are presented under the classifications such as cells, plants, invertebrates, vertebrates and humans.

Response of extreme haloarchaeon Haloarcula argentinensis RR10 to simulated microgravity in clinorotation

Gravity is the fundamental force that may have operated during the evolution of life on Earth. It is thus important to understand as to what the effects of gravity are on cellular life. The studies related to effect of microgravity on cells may provide greater insights in understanding of how the physical force of gravity shaped life on Earth. The present study focuses on a unique group of organisms called the Haloarchaea, which are known for their extreme resistance to survive in stress-induced environments. The aim of the present investigation was to study the effect of simulated microgravity on physiological response of extremely halophilic archaeon, Haloarcula argentinensis RR10, under slow clinorotation. The growth kinetics of the archaeon in microgravity was studied using the Baryani model and the viable and apoptotic cells were assessed using propidium iodide fluorescent microscopic studies. The physiological mechanism of adaptation was activation of ‘salt-in’ strategy by intracellular sequestration of sodium ions as detected by EDAX. The organism upregulated the production of ribosomal proteins in simulated microgravity as evidenced by Matrix-assisted laser desorption ionization Time of flight–Mass Spectrophotometry. Simulated microgravity altered the antibiotic susceptibility of the haloarchaeon and it developed resistance to Augmentin, Norfloxacin, Tobramycin and Cefoperazone, rendering it a multidrug resistant strain. The presence of antibiotic efflux pump was detected in the haloarchaeon and it also enhanced production of protective carotenoid pigment in simulated microgravity. The present study is presumably the first report of physiological response of H. argentinensis RR10 in microgravity simulated under slow clinorotation.