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"Enzyme activity can be used as a peat decomposition indicator in the oil palm rhizosphere of peatlands. Oil palm plantation management requires fertilization in the rhizosphere to provide nutrients for oil palm growth. The state of total nutrient in the rhizosphere can influence enzyme activity. This research aimed to study enzyme activity in relationship to nutrients in the oil palm rhizosphere of peatlands. Using the explorative method in Riau’s tropical peatlands, an oil palm plantation was chosen as a location for the main sites, and a degraded forest as well as a shrubland were chosen as comparison sites. In the oil palm plantation, peat samples were taken from peats adhering to oil palm roots at the peat depths of 0‒25 and 25‒50 cm and at distances of 0‒1, 1‒2, 2‒3, and 3‒4 m from the trees. In the degraded forest and shrub, t samples were taken from selected plant roots at the depths of 0-25 and 25-50 cm. The triplicate peat samples were then composited for an analysis of enzyme activity and total nutrient content. Results showed that enzyme (urease, phosphatase, β-glucosidase, and laccase) activity in the oil palm rhizosphere decreased as the distance from trees and the depth of rhizosphere increased. The decline in enzyme activity was caused by a low peat pH and an increased water content as well as organic carbon content. Enzyme activity increased with increasing oil palm age and ash content. Total K and Zn contents showed no correlation with enzyme activities. However, total Ca and Mg contents showed positive correlation only with β-glucosidase activity. Total Fe and Cu contents showed significantly negative correlation with enzyme activities (urease, phosphatase, β-glucosidase, and laccase). Enzyme activity in the rhizosphere of the degraded forest and shrubs were mostly lower than in the oil palm rhizosphere."

"Photoperiod affects fish reproduction as it regulates activities of the endocrine glands, which produce the hormones needed for geonadal growth and development, gametogenesis, and reproductive cycles. This study aimed to determine the effects of photoperiod on the hard-lipped barb’s reproductive performance by exposing the fish to three photoperiod treatments (light hour: L, darks hour: D), namely 14L:10D (control), 8L:16D (short photoperiod) and 18L:6D (long photoperiod), with four aquaria, each containing 9 fish, serving as replicates. The fish were kept under these photoperiods for 8 weeks. Liver activity, the observable variable in the study, was evaluated by measuring vitellogenin gene expression. Normalized data were then subjected to ANOVA, followed by Tukey’s range test. The hard-lipped barb’s vitellogenin cDNA was found have a 1136 bp sequence and the vitellogenin precursors encoded cDNA comprising 378 amino acids. The vitellogenin gene in each experimental group saw a significant increase on average when exposed to longer photoperiods (P<0.05), and the highest levels of vitellogenin gene expression occurred under long photoperiods (LP, 18 h light:6 h dark). These results indicate that longer photoperiods stimulate and improve the hard-lipped barb’s reproductive performance."