Leaf life span plasticity in tropical seedlings grown under contrasting light regimes.
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BACKGROUND AND AIMS: The phenotypic plasticity of leaf life span in response to low resource conditions has a potentially large impact on the plant carbon budget, notably in evergreen species not subject to seasonal leaf shedding, but has rarely been well documented. This study evaluates the plasticity of leaf longevity, in terms of its quantitative importance to the plant carbon balance under limiting light. METHODS: Seedlings of four tropical tree species with contrasting light requirements (Alstonia scholaris, Hevea brasiliensis, Durio zibethinus and Lansium domesticum) were grown under three light regimes (full sunlight, 45 % sunlight and 12 % sunlight). Their leaf dynamics were monitored over 18 months. RESULTS: All species showed a considerable level of plasticity with regard to leaf life span: over the range of light levels explored, the ratio of the range to the mean value of life span varied from 29 %, for the least plastic species, to 84 %, for the most. The common trend was for leaf life span to increase with decreasing light intensity. The plasticity apparent in leaf life span was similar in magnitude to the plasticity observed in specific leaf area and photosynthetic rate, implying that it has a significant impact on carbon gain efficiency when plants acclimate to different light regimes. In all species, median survival time was negatively correlated with leaf photosynthetic capacity (or its proxy, the nitrogen content per unit area) and leaf emergence rate. CONCLUSIONS: Longer leaf life spans under low light are likely to be a consequence of slower ageing as a result of a slower photosynthetic metabolism. (+info)
The impact of plants on the reduction of volatile organic compounds in a small space.
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This study aims at examining the reduction of indoor air contaminants by plants placed in an indoor space. Field measurements were performed using Aglaonema brevispathum, Pachira aquatica, and Ficus benjamiana, which were verified as air-purifying plants by NASA. Three conditions for the amount of plants and positions were used in two separate rooms whose dimensions are identical. The concentration of Volatile Organic Compounds (VOCs) was monitored three hours after the plants were placed and three days after the plants were placed. The variations of concentration of Benzene, Toluene, Etylbenzene, and Xylene (BTEX), as well as Formaldehyde, which are all known as the major elements of Volatile Organic Compounds were monitored. The amount of reduction in concentration of Toluene and Formaldehyde was monitored 3 hours and 3 days after the plants were placed in the space. The reduction in the concentration of Benzene, Toluene, Etylbenzene, Xylene, and Formaldehyde was significantly greater when plants were present. When plants were placed near a window, the reduction of concentration was greater. The more plants were used, the more a reduction of indoor air contaminants occurred. The effect of reducing the concentration of air contaminants increased when the amount of plants increased, and when the plants were placed in sunny area. The concentration of Toluene was reduced by 45.6 microg/m(3) when 10% of the model space was occupied by Aglaonema brevispathum. (+info)
Glycemic index of common Malaysian fruits.
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The objective of the present study was to measure the glycemic index of durian, papaya, pineapple and water-melon grown in Malaysia. Ten (10) healthy volunteers (5 females, 5 males; body mass index 21.18+/-1.7 kg/m2) consumed 50 g of available carbohydrate portions of glucose (reference food) and four test foods (durian, papaya, pineapple and watermelon) in random order after an overnight fast. Glucose was tested on three separate occasions, and the test foods were each tested once. Postprandial plasma glucose was measured at intervals for two hours after intake of the test foods. Incremental areas under the curve were calculated, and the glycemic index was determined by expressing the area under the curve after the test foods as a percentage of the mean area under the curve after glucose. The results showed that the area under the curve after pineapple, 232+/-24 mmolxmin/L, was significantly greater than those after papaya, 147+/-14, watermelon, 139+/-8, and durian, 124+/-13 mmolxmin/L (p<0.05). Similarly, the glycemic index of pineapple, 82+/-4, was significantly greater than those of papaya, 58+/-6, watermelon, 55+/-3, and durian, 49+/-5 (p<0.05). The differences in area under the curve and glycemic index among papaya, watermelon and durian were not statistically significant. We conclude that pineapple has a high glycemic index, whereas papaya is intermediate and watermelon and durian are low glycemic index foods. The validity of these results depends on the accuracy of the data in the food tables upon which the portion sizes tested were based. (+info)
Transient response of sap flow to wind speed.
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Durian may inflict severe body injury when it drops from the tree. This case report describes a patient who presented with facial and penetrating eye injury when a ripe durian fruit dropped onto her face while harvesting the fruits under the tree. The authors emphasized the importance of facial and eye protective devices during durian fruit harvesting season. (+info)
Influence of chemical extraction conditions on the physicochemical and functional properties of polysaccharide gum from durian (Durio zibethinus) seed.
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Effect of different purification techniques on the characteristics of heteropolysaccharide-protein biopolymer from durian (Durio zibethinus) seed.
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