Graduate Thesis Or Dissertation
 

Sugar uptake, fruit growth and carbon partitioning in the strawberry

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/k930c161b

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  • Sinks, plant organs which depend on the import of assimilates for growth, play a central role in determining assimilate distribution patterns within the plant. The strawberry fruit is a strong sink for dry matter and its effect on carbon partitioning and assimilation in the plant as well as the mechanism by which dry matter is assimilated by the fruit were studied. All experiments were conducted with day-neutral strawberries (Fragaria X ananassa Duch. cv Brighton) grown in a greenhouse. Plants were deblossomed to determine the effect of fruiting on plant growth. Fruit was the dominant sink accumulating 16 g dry weight/plant and during the peak of fruit growth, fruit accumulated more dry matter than assimilated by the entire plant. Fruit limited the growth of all vegetative plant parts. During the peak of fruit growth net photosynthesis per unit area of single leaves was 60-80% higher in fruiting plants than in deblossomed plants. To determine the chemical form in which dry matter arrived at the fruit, labeled photosynthate was collected from the phloem of cut pedicels. Radioactive label in the phloem exudate was found to be primarily in sucrose (92%) with the remainder in glucose (2%), fructose (1%) and acidic and basic fractions (4%). Growth of a strawberry fruit was dependent upon its ranking within an inflorescence. Primary fruit had the largest diameter, fresh weight, dry weight, expansion rate and relative growth rate from anthesis until fruit were ripe. All of these parameters decreased with lower ranking on the inflorescence. Rates of ¹⁴C-sucrose uptake by fruit tissue discs cut from fruit having different growth rates were similar to rates of dry matter accumulation into the fruit in situ. Uptake of ¹⁴C-sucrose into fruit tissue discs was greatest at a pH of 5.0 and 40°C. High concentrations of metabolic inhibitors such as dinitrophenol stimulated sucrose uptake while reducing respiration and incorporation of label into insoluble components. Kinetic analysis of sucrose uptake revealed a linear and a saturable component. The uptake rates of fructose and glucose, which are the products of sucrose hydrolysis, were measured. The rates of fructose uptake were similar to that of sucrose, but glucose uptake was 2-3 fold greater and exhibited saturation kinetics.
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