The decomposition of organic matter influences CO2 flux in peat soils. However, determination of the flux from the decomposition process is usually over-estimated because the total CO2 flux calculation includes root respiration. We clarified this issue addressing the following aims: (i) to study the relation of oil palm root distribution in peat soils to the flux and (ii) to estimate the relative contribution of root respiration and peat decomposition to the total CO2 flux. The study was conducted between January and June 2012. In the research area, three transects were established perpendicular to drainage channels, where nine14-year-old oil palm trees were selected and used as observation sites. Eight closed chambers were established as observation points at each site. We measured CO2 flux at each point using an Infra Red Gas Analyzer (IRGA). Root and peat samples were collected from each observation point to measure root density and analyze peat chemical properties. Our results showed that the pHH2O and nutrient content of P, K, Ca and Mg in the peat soils significantly increased of CO2 flux. Oil palm roots at depths of 0–15 and 15–30 cm nearest the tree showed the highest density, while root densities gradually decreased with increasing distance from the tree. CO2 flux in the peat soils nearest to the tree were highest at 0.44 ± 0.23 mg CO2 m-2 sec-1 (or 137.7 ± 73.4 t CO2 ha-1 yr -1). CO2 flux significantly decreased with increasing distance from the tree, showing the lowest value of 0.10 ± 0.04 mg CO2 m-2 sec-1 (or 30.67 ± 12.4 t CO2 ha-1 yr -1). We conclude that the CO2 flux was derived from peat decomposition and root respiration. Using the integral equation approach, the relative contribution of root respiration and peat decomposition was 74 and 26%, respectively to the total CO2 flux.
Capsicum chinense is thought to have been domesticated in the lowlands east of the Andes Mountains in South America. It is grown in Southeast Asia, but its distribution there remains unknown. We conducted literature, specimen, field, and market surveys of C. chinense in Indonesia to investigate its introduction into Indonesia and to determine its current distribution. One dried specimen collected in 1912 and stored as Capsicum sp. appears to be either C. frutescens or C. chinense. An illustration of C. frutescens in Ochse (1931), which actually appears to be C. chinense, suggests that C. chinense may have been introduced into Indonesia before World War II; however, the distribution of C. chinense in Southeast Asia remains very limited to this today. In Indonesia, C. chinense is distributed widely on at least the three major islands of Java, Kalimantan, and Sulawesi with several morphologically different fruit types; it is used as an ornamental plant as well as a spice. Four species of the genus Capsicum, including C. annuum, C. frutescens, C. pubescens, and C. chinense, are distributed in Indonesia, which suggests that Indonesia has more genetic resources and more potential to breed species of Capsicum than other countries in Southeast and East Asia.
Durian is known to set fruit poorly or generate uneven-shaped fruits when exposed to temperatures below 20°C at anthesis. However, the effect of temperature on pollen-tube elongation during style or ovule development is not fully understood. In this study, the effects of temperature on pollen germination, pollen-tube elongation, and fruit set were investigated in ‘Monthong’ durian. First, pollen germination on agar media was tested at 10, 15, 20, 25, 30, and 35°C. Pollen-tube kinetics in emasculated fresh style was observed at the same temperatures until 48 h after pollination. At 20 and 25°C, more than 45% of pollen grains germinated throughout the 2-year observation period. At 20, 25, and 30°C, pollen tubes reached the base of the style within 48 h. Pollen-tube elongation was inhibited at 15 and 35°C. Next, the night (2000 to 0800 h) temperature around the flowers was fixed at 15 or 25°C for 7 nights in an orchard, after which pollen-tube elongation and ovule development at 7 days after pollination (DAP) were investigated. Pollen tubes reached the base of the style at both temperatures; however, at 15°C, ovules remained at the mature stage before accepting the pollen tube. Ovule development at 25°C progressed to the endosperm nuclei division stage, which was indicative of fertilization. Flowers or fruits abscised markedly at 15°C by 14 DAP. Based on these results, night temperatures below 15°C during anthesis inhibit fertilization in ‘Monthong’ durian. Additionally, flower abscission at 15°C was caused by failed fertilization.
NERICA (new rice for Africa) varieties (Oryza sativa x O. glaberrima x O. sativa), which, with their strong drought tolerance, are expected to promote upland rice cultivation in sub-Saharan Africa, could be grown in lowland conditions. Field experiments were conducted at the experimental farm of National Crop Resources Research Institute in Uganda for four crop seasons in 2010 and 2011 under upland and lowland field conditions using three upland NERICA varieties in order to (i) compare crop performance between upland and lowland rice ecosystems and (ii) identify attributes responsible for the yield gap between upland and lowland ecosystems. Results indicated that on average, the yield under lowland condition was higher than under upland condition by 25%. With favorable rainfall conditions, the yield under upland ecosystem was the same as, or even better than that of lowland ecosystem for the same varieties. Among the yield components assessed, the number of panicle m-2 and the number of spikelets per panicle were key factors that contributed to yield under upland condition, and the number of spikelets per panicle was the single significant factor contributing to yield under lowland condition. The differences in these two yield components, the number of spikelets per panicle in particular, were responsible for the yield gap between lowland and upland. These characteristics are common to Oryza sativa, but more distinct for upland NERICAs.
Mangoes are the fruits of Mangifera species, most of which are distributed in Southeast Asia. M. caloneura Kurz is a common wild mango in mainland Southeast Asia where it is utilized locally for its edible fruit. This species has been a subject of recent attention in explorations of mango folk taxonomy. However, species assignment to M. caloneura is difficult because there are two different descriptions: one indicates the presence of only 1 fertile stamen per flower and the second indicates 5 fertile stamens. The type diagnosis by Kurz describes 1 fertile stamen per flower; nevertheless, Kurz has been retained as the binomial authority in all subsequent literature, even in works describing the presence of 5 fertile stamens. Here, we track taxonomic developments over 138 years to demonstrate how inconsistencies have arisen.