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Physiological responses of pineapple (Ananas comosus (L.) Merr.) to CO₂ enrichment, temperatures and water deficit
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|Title:||Physiological responses of pineapple (Ananas comosus (L.) Merr.) to CO₂ enrichment, temperatures and water deficit|
|Keywords:||Pineapple -- Physiology|
|Abstract:||The over goal of this project was to understand the physiological mechanisms by which pineapple (Ananas comosus [L.] Merr.), a species having Crassulacean acid metabolism (CAM), will respond to the increase in atmospheric CO2 and environmental temperatures projected to occur over the next century. The treatments in present study consisted of CO2 concentrations of near ambient 350 µmol mol^-1 and twice ambient (700 µmol mol^-1), and day/night temperatures of 30/20, 30/25 and 35/35°C. Experiments were conducted by growing plants in these environments for six months or more and measuring the physiological responses when plants were exposed to the two CO2 levels, with long-term as plants grown at ambient/elevated CO2 and measured at ambient/elevated CO2, and short-term as plants grown at ambient/elevated CO2 and measured at elevated/ambient CO2 environment. The specific objectives were designed to 1) study the responses in leaf gas exchange and stomatal conductance to CO2 and temperatures, 2) quantify the effects of CO2 and temperatures on biomass accumulation and partitioning, 3) investigate the some physiological responses, including accumulation of organic acids, nitrogen and chlorophyll contents, chlorophyll fluorescence and carboxylating enzyme activities, and 4) examine the effects of prolonged water deficit to leaf water relations, gas exchange and acidification under ambient and elevated CO2 and three day/night temperatures. Two major experiments were conducted. In the first experiment, plants were grown at ambient CO2, while in the second experiment, the responses of plants to elevated CO2 was examined. After pineapple was adapted to CO2 and temperatures in growth chambers for six months, a water deficit was imposed on some of the plants by withholding irrigation for two months to study the effect of water deficit. An additional experiment was conducted in open-top chambers to examine the response of pineapple to ambient and elevated CO2. CAM activity of pineapple was intensified at a day/night temperature differential of 10 OC, while the relative contribution of the C3-type photosynthetic pathway to carbon assimilation was enhanced where the daily temperature range was 5°C and night temperature of 25°C. Elevated CO2 enhanced daily CO2 fixation, but reduced stomatal conductance, thus increasing water use efficiency, and the effect was greatest during light period. Carbon isotopic discrimination data indicated that the relative contribution of C3 pathway to CO2 fixation was enhanced by elevated CO2 at all temperatures. There was a significant temperature by CO2 interaction on leaf gas exchange. Daytime CO2 fixation was greatly increased by elevated CO2, and nocturnal fixation and acidification were also enhanced, which was in contrast to some studies on CAM species. Elevated CO2 promoted biomass accumulation in pineapple due to increased net assimilation rate, with the greatest effect at smaller daily temperature differential of 5°C. At twice ambient C2, more biomass was partitioned to stem and root, but less to leaf. Elevated CO2 also enhanced stem and leaf dry matter contents, and increased leaf thickness and rate of surface area expansiol1. Leaf nitrogen and chlorophyll contents were reduced at elevated CO2 for plants grown in growth chambers, but there was no such response for plants grown in open-top chambers due to improved nutrient management. Prolonged drought reduced leaf water content and water potential components, with greater effect on plants grown at night temperature of 25°C. Diurnal gas exchange and stomatal conductance also decreased, and the effect was greater in the light period. Therefore, the reduction in CO2 fixation due to stomatal closure was greater for plants grown at elevated CO2, especially, early in the drought. Reduced nocturnal acidification resulted in CAM-idling for plants grown at night temperature of 25°C. The decrease in tissue water content and water potential components were relatively lower in higher CO2 environment. Lower night temperature also help to sustain relative higher leaf water status and accumulation of organic acids as drought became severe.|
|Description:||Thesis (Ph. D.)--University of Hawaii at Manoa, 1996.|
Includes bibliographical references (leaves 125-138).
vi, 138 leaves, bound ill. 29 cm
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|Appears in Collections:||CTAHR Ph.D Dissertations|
Ph.D. - Agronomy and Soil Science
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