Simulated Microgravity Effects on Shoot Parameters and Antioxidant Potentials of Three Essential Economic Crops: A Case Study of Abiotic Stressors

Abstract

<title>Abstract</title> Spaceflight-microgravity experiments are unusual and expensive. Thus, using microgravity-simulators such as Clinostat has enhanced microgravity research on Earth. Gravity reduction causes significant changes in chosen biological organisms, macromolecules, fluids or materials. These changes have led to discoveries that are of social-economic benefits. Consequently, there is a need to work on Clinostat Simulated-Microgravity Models (CS-MM) on essential-economic crops (peanut, corn, tomato) that would have inherent nutritional values far better than their terrestrial counterparts. CS-MM was therefore used to determine the effects of gravity-variations on shoots parameters and antioxidant potentials of the newly emerged crops. Furthermore, the effects of abiotic stresses; salinity [NaCl; 30mM-100mM] and heavy metal [Pb(NO₃)₂; 30mM-100mM] were determined as the cultivation of unstressed and stressed seedlings were nurtured to maturity by continual application of NaCl and Pb(NO₃)₂. Seeds were grown under normal Earth’s gravity (1g-control) and under CS-MM. The Clinostat experimental-variables are rotation-speed, rotational-axis angle and rotation-direction. The antioxidant-potentials were determined via: phytochemical-contents, their scavenging-activities on free-radicals through DPPH (2,2-diphenylpicrylhydrazyl), FRAP (Fluorescence Recovery After Photobleaching) and ABTS (2,2-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) while the antioxidant enzymes assay of polyphenol-oxidase (PPO), peroxidase (POD) and catalase (CAT) were subsequently carried out and read with ELISA (Enzyme-Linked-Immunosorbent Serologic Assay) spectrophotometer. Results revealed that the plant developments (shoot-height and leaf-number) decreased with continual applications of NaCl and Pb(NO₃)₂. Although, CAT did not have significant effect on all the experimental treatments for corn and tomato, higher quantities of essential phytochemicals, PPO and POD activities at varying-levels of significant activities depending on experimental treatments were observed. Overall, the obtained CS-MM crops produced better yields and have abilities to withstand environmental stresses. Thus, to these synergized efforts, aside the on-Earth benefits, space-explorers in distant future can have improved-breeds of crops from this research that may adapt and survive well in the harsh environment of space.