The potential involvement of activated oxygen species by submergence stress was studied in two Malaysian rice cultivars, MR219-4 and MR219-9, and cultivar FR13A that is known to be tolerant to submergence. Seedlings of these three rice cultivars were subjected to different submergence periods (4, 8, and 12 days). Under 8 days of complete submergence, FR13A cultivar showed higher lipid peroxidation in terms of malondialdehyde level and activities of antioxidative enzymes, superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR) when compared to the MR219-4 and MR219-9 cultivars. MR219-9 showed higher SOD, APX, and GR activities after 12 days of submergence. The levels of SOD activity indicated that detoxification of O 2 Á-to H 2 O 2 was maintained at a stable level throughout the submergence stress until up to 8 days and increased rapidly at 12 days of submergence. The results indicated that tolerance to submergence in rice is associated until 8 days submergence for MR219-4 and FR13A cultivars. These findings suggested that tolerance to submergence stress in rice might be proven by increased the capacity of antioxidative system. In addition, CAT activity has much higher affinity for scavenges H 2 O 2 than APX. Therefore, ascorbate glutathione cycle might be more efficient to scavenge H 2 O 2 .
Abstract. Siregar LAM, Angkat NU, Damanik RI. 2021. Characterization and evaluation of the variability of dragon fruit accessions in Dairi District, North Sumatra Province, Indonesia. Nusantara Bioscience 13: 138-145. Many types of dragon fruits were planted in Dairi District of North Sumatra Province without much information of their importance in economic values. Therefore, this study was carried out to evaluate the variability of the dragon fruit population in this region to assist the local farmers in selecting the best species for planting. This study used a morphological observation method based on dragon fruit descriptor employing a purposive sampling technique. A total of 56 dragon fruit accessions collected from Sidikalang, Sitinjo, and Siempat Nempuhulu Sub-districts were studied and characterized based on the morphological characteristics of stems, flowers, and fruit. The results showed some variations in the stem, flower, and fruit morphology among the studied population. The dragon fruit plant that is widely cultivated by farmers in three sub-districts of Dairi District is a species of Hylocereus polyrhizus. Phenotypic diversity analysis showed seven quantitative characters with broad criteria of eighteen characters observed, namely stem length, pericarpel length, number of lobes, flower shoot length, number of bractea, bractea peak length, and fruit weight. However, phenotypic diversity analysis indicates they are closely related to each other except for accession D17 the red dragon fruit or red pitaya (Hylocereus spp.), and it could be the exotic species for nation-wide planting in Indonesia.
The effect of oxygen deprivation (anoxia) on the antioxidant system in suspension culture of anoxiaintolerant Malaysian rice mutants cells was examined. Abiotic stresses have been reported to adversely affect cell division, damage cellular and organelle membranes. The signaling defense mechanisms, such as molecular and biochemical aspects responding to stress have been proven to be very complex, and still largely untapped. The objective of this study was to determine the potential involvement of activated oxygen species, such as superoxide dismutase, catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase which occur in cells of rice plants exposed to anoxia stress in two Malaysian rice mutants, MR219-4 and MR219-9, and rice cultivar FR13A which is known to be tolerant to anoxia stress during 5-30 days of exposure. The antioxidative enzymes were decreased for MR219-4 and MR219-9 mutants for CAT and APX activities, and increased in FR13A cultivar starting at 20 days in suspension culture compared to that of control. CAT and APX activities were maintained higher in anoxia condition for all mutants and cultivar. These findings suggested that anoxia stress in suspension cultures induced the level of H 2 O 2 to toxic levels.
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