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Water content and carbohydrate dynamics of pear trees during dormancy in Southern Brazil

Simoes, F., Hawerroth, F. J., Yamamoto, R. R., Herter, F. G.
Acta horticulturae 2014 no.1058 pp. 305-312
budbreak, buds, carbohydrate content, carbohydrate metabolism, climatic factors, cold treatment, dormancy, ecophysiology, fruit trees, pears, shoots, starch, sugars, temperate zones, temperature, water content, winter, Brazil
The winter ecophysiology in temperate zone fruit trees is characterized by the water movement, carbohydrate metabolism as well as an inertial state variable in buds, during para-, endo-, and eco-dormancy stages. The objective of this study was to characterize the water dynamics and its relation with carbohydrate mobilization in buds and surrounding tissues during dormancy progression, in European and Japanese pear trees grown under different climatic conditions. Shoots were collected from plants grown in Vacaria-RS (625 chilling hours below 7.2°C (CH), and at São Joaquim-SC (780 CH) during the 2008 winter season. Tissues (stem and bud+bud cushion) were separated and dried to determine water content (WC), soluble sugars content (SS) and starch content (SC), at six dates (23 May, 14 Jun, 5 Jul, 26 Jul, 16 Aug, and 3 Sept). The mean time for bud break (MTB) of apical buds was determined for each date. The WC in tissues as a marker of dormancy progression seems to be valid for ‘Packham’s Triumph’. Renewal of growth coincided with a significant increase in the WC in buds of the plants grown in São Joaquim. However, a similar relationship was not observed in ‘Housui’. High temperatures during dormancy might alter the water dynamics in ‘Packham’s Triumph’, but not in ‘Housui’, when cultivated at different levels of CH accumulation. Total soluble sugars content increased 52% in buds of ‘Packham’s Triumph’ grown under higher chilling accumulation condition in the third sampling date (5 Jul). Starch to soluble sugar conversion was observed clearly in European pear grown under higher chilling accumulation in bud + bud cushion.