Chilling privation during dormancy period and carbohydrate mobilization in Japanese pear trees

The flower bud abortion is one of the main problems that limit commercial pear (Pyrus pyrifolia) production in the southern region of Brazil. Insufficient chilling during the dormancy period is known as the main factor of this problem. One of the hypotheses to explain this problem is that the starch mobilization and carbohydrate fluxes to the buds are impeded when mild temperatures occurred during winter. This study compared the total soluble sugars (TSS) and reducing sugars (RS) concentrations, the cell wall acid invertase (CWAI - EC 3.2.1.26) and sucrose-phosphate synthase (SPS - EC 2.4.1.14) activities in wood of branches and floral buds of Japanese pear trees cv. Housui, grafted on Pyrus calleryana and submitted to chilling conditions during the dormancy period. Treatments were: (i) natural conditions; (ii) continuous artificial chilling; (iii) alternating temperatures, and (iv) total chilling privation. TSS and RS contents, as well as CWAI and SPS activities in tissues of branches that received insufficient chilling were lower than those that received sufficient chilling during winter. The starch concentration was superior in wood tissues of branches kept under chilling privation. The chilling privation disturbs carbohydrate mobilization in pear trees, reducing the sucrose synthesis capacity in wood tissues (source) and sucrose importation by the floral buds (sink).

Chilling privation during dormancy period and carbohydrate mobilization in Japanese pear trees

The flower bud abortion is one of the main problems that limit commercial pear (Pyrus pyrifolia) production in the southern region of Brazil. Insufficient chilling during the dormancy period is known as the main factor of this problem. One of the hypotheses to explain this problem is that the starch mobilization and carbohydrate fluxes to the buds are impeded when mild temperatures occurred during winter. This study compared the total soluble sugars (TSS) and reducing sugars (RS) concentrations, the cell wall acid invertase (CWAI - EC 3.2.1.26) and sucrose-phosphate synthase (SPS - EC 2.4.1.14) activities in wood of branches and floral buds of Japanese pear trees cv. Housui, grafted on Pyrus calleryana and submitted to chilling conditions during the dormancy period. Treatments were: (i) natural conditions; (ii) continuous artificial chilling; (iii) alternating temperatures, and (iv) total chilling privation. TSS and RS contents, as well as CWAI and SPS activities in tissues of branches that received insufficient chilling were lower than those that received sufficient chilling during winter. The starch concentration was superior in wood tissues of branches kept under chilling privation. The chilling privation disturbs carbohydrate mobilization in pear trees, reducing the sucrose synthesis capacity in wood tissues (source) and sucrose importation by the floral buds (sink).

Mild temperatures on bud breaking dormancy in peaches

The search for low chill cultivars for peach production in areas with low chill accumulation (temperatures below 7.2°C) has stimulated studies about the higher temperatures effects on low chill cultivars. The objective of this research was to evaluate the influence of mild temperatures on flowering and leafing of 'Turmalina' and 'Ágata' cultivars with low and medium low chilling requirements, respectively. Plants obtained by grafting flower twigs in the autumn, after the grafting, were submitted to chilling treatments (150, 250, 350, 500 and 672 hours) at three temperature levels (5°C, 10°C and 15°C). After the end of the treatments, the plants had been taken to greenhouse (20°C±5°C) and evaluated weekly. The results showed that satisfactory flower and leaf development occur even at temperatures as high as 15°C for a period of 150 hours, in 'Turmalina' peach. Temperatures of 10°C for a period equal or superior to 350 hours promote satisfactory leafing in 'Ágata' peach. Temperatures of 10°C and 15°C cause earlier development of flowers and leaves in both cultivars when compared to 5°C.

A busca por cultivares pessegueiro com baixa necessidade em frio para regiões com pouco acúmulo de frio (temperaturas abaixo de 7,2°C) tem estimulado estudos sobre o efeito de altas temperaturas sobre cultivares de baixa necessidade de frio. O objetivo desta pesquisa foi avaliar a influência de temperaturas amenas na floração e brotação da 'Turmalina' e 'Ágata', duas cultivares com baixa e média necessidade de frio, respectivamente. Plantas obtidas por enxertia no outono foram submetidas a tratamentos de frio (150, 250, 350, 500 e 672 horas) em três níveis de temperatura (5°C, 10°C e 15°C). Após os tratamentos, estas plantas foram colocadas em casa de vegetação a temperatura de 20°C±5°C e avaliadas semanalmente. Conclui-se que temperatura de até 15°C por um período de 150 horas é capaz de resultar em floração e brotação satisfatórias para a cultivar 'Turmalina'. Temperaturas de 10°C por um período igual ou superior a 350 horas promovem brotação satisfatória na cultivar 'Ágata'. Temperaturas de 10°C e 15°C comparadas a 5°C causam antecipação da floração e brotação e ambas cultivares.

Mild temperatures on bud breaking dormancy in peaches

The search for low chill cultivars for peach production in areas with low chill accumulation (temperatures below 7.2°C) has stimulated studies about the higher temperatures effects on low chill cultivars. The objective of this research was to evaluate the influence of mild temperatures on flowering and leafing of 'Turmalina' and 'Ágata' cultivars with low and medium low chilling requirements, respectively. Plants obtained by grafting flower twigs in the autumn, after the grafting, were submitted to chilling treatments (150, 250, 350, 500 and 672 hours) at three temperature levels (5°C, 10°C and 15°C). After the end of the treatments, the plants had been taken to greenhouse (20°C±5°C) and evaluated weekly. The results showed that satisfactory flower and leaf development occur even at temperatures as high as 15°C for a period of 150 hours, in 'Turmalina' peach. Temperatures of 10°C for a period equal or superior to 350 hours promote satisfactory leafing in 'Ágata' peach. Temperatures of 10°C and 15°C cause earlier development of flowers and leaves in both cultivars when compared to 5°C.

A busca por cultivares pessegueiro com baixa necessidade em frio para regiões com pouco acúmulo de frio (temperaturas abaixo de 7,2°C) tem estimulado estudos sobre o efeito de altas temperaturas sobre cultivares de baixa necessidade de frio. O objetivo desta pesquisa foi avaliar a influência de temperaturas amenas na floração e brotação da 'Turmalina' e 'Ágata', duas cultivares com baixa e média necessidade de frio, respectivamente. Plantas obtidas por enxertia no outono foram submetidas a tratamentos de frio (150, 250, 350, 500 e 672 horas) em três níveis de temperatura (5°C, 10°C e 15°C). Após os tratamentos, estas plantas foram colocadas em casa de vegetação a temperatura de 20°C±5°C e avaliadas semanalmente. Conclui-se que temperatura de até 15°C por um período de 150 horas é capaz de resultar em floração e brotação satisfatórias para a cultivar 'Turmalina'. Temperaturas de 10°C por um período igual ou superior a 350 horas promovem brotação satisfatória na cultivar 'Ágata'. Temperaturas de 10°C e 15°C comparadas a 5°C causam antecipação da floração e brotação e ambas cultivares.