Gravity Variation Effects on the Growth of Maize Shoots

Gravity-variation effects on plants give definite changes. Normal-earth-gravity (1G) and microgravity (µg) are possible variations for experimental purposes. On-board spaceflight microgravity-experiments are rare and expensive, as microgravity-environment is an outstanding platform for research, application and education. Clinostat was used for ground-based experiment to investigate the shoot-morphology of maize plants at the Space-Agency of Nigeria – National Space Research and Development Agency (NASRDA). A Clinostat device uses rotation to negate gravitational-pull effects on plant growth and development. Maize was selected for this experiment because of its nutritional and economic importance; and its usability on the Clinostat. Plant shoot-morphology is important for gravi-responses. Shoot curvature and shoot growth-rate analyzes were done on the shoots of provitamin variety of maize. The seeds were planted into 3 petri-dishes (in-parallels) in a wet-chamber using plant substrate – agar-agar. The experimental conditions were subject to relative-humidity, temperature and light-conditions. After 3 days of germination under 1G, two of the petri-dishes were left under 1G serving as controls for shoot curvature and shoot growth-rate analyzes. The clinorotated-sample was mounted on Clinostat under: fast rotation-speed of 80 rpm, horizontal rotation position and clockwise rotation-direction. The images of the samples were taken 30 minutes interval for 4 hours. After observations, the shoot morphology of the seedlings were studied using ImageJ-software. The grand-average shoot-angles and shoot-lengths of all the seedlings were calculated following the experimental period to give the shoot curvatures and shoot growth-rates respectively. The results showed that the clinorotated-sample had reduced response to gravity with 12.69°/hr for the shoot-curvature while the 1G-sample had 13.87°/hr. The shoot growth-rate for the 1G-sample was 0.31mm/hr while the clinorotated was 0.32mm/hr. The clinorotated had increased growth-rate per hour than the counterpart 1G. These analytical results serve as a preparation for future real-space experiments on maize and could be beneficial to agriculture-sector.