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Different thermal conditions during ecodormancy in Japanese pear affect floral bud necrosis, water and carbohydrate dynamics

Horikoshi, H. M., Sekozawa, Y., Sugaya, S., Yamamoto, R. R., Herter, F. G.
Acta horticulturae 2017 no.1160 pp. 221-226
buds, cold treatment, dormancy, glucose, heat, heat sums, metabolism, necrosis, pears, shoots, sucrose, temperature, water content
In order to clarify thermal fluctuation effects during ecodormancy on floral bud necrosis, 'Kousui' Japanese pear shoots were collected after 900 accumulated chilling hours (below 7.2°C) under natural conditions and exposed to three different conditions: constant 25°C (Treatment 1); fluctuating 25/15°C (12/12 h) temperatures (Treatment 2); and 25/15°C (12/12 h) with drastic reductions of temperature to 5°C (12 h) four sampling times (after exposure to accumulated temperatures of 2000, 4000, 6000, 8000 GDH) during the ecodormant phase (Treatment 3). Floral bud necrosis increased through dormancy release and heat accumulation, and buds exposed to extreme thermal fluctuation conditions (25/15°C+5°C) exhibited the highest amount of necrosis. Water content was lowest in buds exposed to 25/15°C+5°C. Sucrose concentration in buds undergoing extreme thermal fluctuation was highest at the end of heat accumulation period, suggesting low sucrose catabolism. Glucose content increased earlier shoots kept at a constant 25°C during the heat accumulation period, indicating higher availability of this carbohydrate for growth resumption. It is suggested that thermal fluctuations during ecodormancy lead to reductions of both water and glucose content, and a possible low catabolism of sucrose that increased both the occurrence and severity of floral bud necrosis.