GERMINATION STUDIES AND ANTIOXIDANT ASSESSMENT OF Zea mays

    ABSTRACT

Modification of physiological processes may be used to offset the negative effects of gravity on plant growth and development. This study was set up to assess the efficacy of indole-3-acetic acid (IAA) in improving the germination characteristics of Zea mays (O cultivar) and antioxidant assessment in microgravity. The seeds were primed with IAA solutions, which were then divided into two concentrations: 100 and 500 mg/L. The primed maize seeds were then inoculated and mounted on the Clinostat at 0.5 and 2.5rpm for 72 hrs. Under microgravity, the germination of maize was found to be impaired. However, germination was increased when IAA was used under the simulated microgravity conditions. From the experiment conducted, the results showed that germination was observed after 48hrs in the control, whereas in the seed exposed to 100ppm of IAA, under the influence of gravity germination was 60% at the 24hrs compared to 50% at 48hrs in the control. When seeds were exposed to 0.5rpm microgravity with 100ppm IAA under microgravity at 0.5rpm % germination at 24hrs was 65%. By the 72hrs germination % has reached 100% when seeds exposed to 100ppm of IAA were rotated at 0.5rpm and 2.5 rpm respectively. Generally, however, it was observed that all the seeds whether clinorotated or not in the various conc (100ppm, 500ppm, IAA) used in the experiment showed early germination compare to the control. An attempt was made to investigate whether differences in antioxidant enzymes in the shoots, roots and the germinated seeds of the treated and controlled seeds were significantly different. The results showed that for superoxide dismutase where concentration varied from 73.21units to 95.49units, there were no significant differences in SOD contents when comparing those in the shoots, roots and the seeds whether or not the germinant was exposed to clinorotation. Similar situations were reported for catalase and glutathione Peroxidase. However, for Glutathione Peroxidase, report shows that there were significant differences between Glutathione Peroxidase concentration when comparing those seeds exposed to clinorotation and those that were not exposed, for example concentration in Glutathione  Peroxidase in seeds exposed to IAA at both 100ppm and 500ppm and exposed to clinorotation shows significant differences in concentrations in shoots, roots and seeds. Result shows that although there were no significant differences between Glutathione Peroxidase concentration when comparing outcomes for those seeds that were exposed to clinorotation and those that were not exposed to clinorotation. Results also showed that Glutathione Peroxidase concentration in the shoots were significantly higher when comparing those in the root and in the germinated seeds. MDA concentration for seeds treated with the respective plant group promoters and exposed to microgravity. Apart from those seeds exposed to IAA where there were significant differences in concentrations in the shoots, roots and seeds no differences were generally reported in the control, the level of significant differences in MDA was higher when compared to other antioxidants enzymes. The result of proline in 1AA of the different (100ppm and 500ppm) and clinorotation (0.5rpm and 2.5rpm) are (1.06 to 2.83 µmol/g) were significantly lower compared to the standard (3.5 to 5.3 µmol/g). The application of IAA showed an increased plant germination response and the influence of treatments on the enzymatic and non-enzymatic antioxidant activities on germinant (Zea mays). The use of IAA presents a promising method that will help to reduce the harmful effects of microgravity on crop plants.