Partial Submergence Tolerance in Rice (<i>Oryza sativa</i> L.) Cultivated in North Sulawesi at the Vegetative Phase

Beneficial Root-Associated Microbiome during Drought and Flooding Stress in Plants

Crop productivity is seriously threatened by the rise in the frequency and severity of drought and flood events around the world. Reduced drought and flooding stress in vulnerable species and ecosystems depends on our ability to comprehend how drought and flooding affect plant physiology and plant-associated microbes. Involvement of both abscisic acid ABA-dependent and ABA-independent pathways has been noted during drought. Hypoxic conditions impede hydraulic conductance, nutrient uptake and plant growth and development, as well as root aerobic respiration. The root microbiome, which works with the roots during drought and flood, is made up of plant growth-promoting rhizosphere, endophytes and mycorrhizas. A large number of phytohormones, primarily auxins, cytokinin and ethylene, as well as enzymes like 1-Aminocyclopropane-1-Carboxylate deaminase (ACC deaminase) and metabolites like exopolysaccharides are produced by rhizospheric microbes. These phytohormones, enzymes and metabolites have role in the induction of systemic drought tolerance in plants. Under hypoxia, anaerobic microbes with the potential to harm the plant due to their pathogenic behavior or soil denitrification ability are more likely to be present in the rhizosphere and roots. This review concentrates on the primary mechanisms of plant-microbe interactions under drought and flood stress as well as the importance of flood and drought-tolerant microbes in maintaining and increasing crop plant productivity under stress.

Physiological Responses to Drought in Six Rice (<i>Oryza sativa </i>L.) Cultivars Cultivated in North Sulawesi, Indonesia

BACKGROUND AND OBJECTIVE

The drought-tolerant crop plants, including rice, are required for fulfilling food requirements when drought occurs in Indonesia. The response to drought stress in rice cultivars could be studied based on the morphological, anatomical and physiological characteristics. This study evaluated the drought tolerance based on the physiological characteristics at the vegetative phase in six rice cultivars cultivated in North Sulawesi, Indonesia.

MATERIALS AND METHODS

The Completely Randomized Design experiment was conducted in the greenhouse by using six rice cultivars (cv. Superwin, Sultan, Ciherang, Serayu, Cigeulis and IR 64) grown in the soil mixture at the vegetative phase. The treatments in this experiment were water deficit (without water for up to 22 days) and well-watered (watering until field capacity). The evaluated physiological characteristics consisted of leaf water content, leaf relative water content, concentrations of chlorophylls (total, a and b) at 0, 7, 14, 17 and 22 days after treatment.

RESULTS

Withholding water for 22 days at the vegetative phase resulted in a decrease of water content and the increase of concentration of chlorophylls (total, a and b) in leaf. There were two categories of drought tolerance in rice observed in this study, i.e. semi tolerant for Cigeulis, Superwin, Serayu, IR 64, Sultan and non-tolerant for Ciherang.

CONCLUSION

Rice cv. Cigeulis, Superwin, Serayu, IR 64 and Sultan were semi tolerant, whereas cv. Ciherang was non-tolerant rice cultivar. Leaf water content was a potential physiological indicator for drought tolerance in rice.