What temperature conditions does an apple tree need to grow?
What temperature is suitable for cultivating apple trees? Please explain. All physiological activities, biochemical reactions, growth and development processes of apple trees must be carried out under certain temperature conditions. Otherwise, their normal growth and development will be inhibited, blocked, damaged, or even lead to death. Therefore, Zhongdi Web has compiled the temperature requirements of apple trees...
What temperature is suitable for cultivating apple trees? Please explain.All physiological activities, biochemical reactions, growth and development processes of apple trees must be carried out under certain temperature conditions. Otherwise, their normal growth and development will be inhibited, blocked, damaged, or even lead to death. Therefore, Zhongdi Web has compiled the temperature requirements of apple trees, listed in detail below for netizens' reference.
I. Apple tree growth temperature:
The temperature required for the life activities, growth and development of apples, in terms of their physiological processes, all have corresponding minimum, optimum and maximum cardinal temperatures. It is generally believed that the minimum temperature for apples is about 5.0°C, the optimum temperature is 13-25°C, and the maximum temperature is about 40°C, and these vary depending on the cultivar, organ, age, growth stage, physiological process and temperature changes, as well as other ecological factors. The optimum average temperature during the growth period also differs among different cultivars.
II. Apple tree flowering temperature:
By calculating the pre-flowering accumulated temperature from the accumulated temperature and flowering period, the apple flowering period can be predicted. In temperate regions, the effective accumulated temperature above 5°C, the minimum temperature for tree growth, is generally used to predict the flowering period. According to research, from when the air temperature reaches 5°C to the beginning of flowering, the average effective accumulated temperature above 5°C is 160-180°C, with little variation among cultivars. However, the length of time to reach the flowering period is affected by air temperature. At a daily average temperature of 7-8°C, most cultivars need about 50 days; at 10°C, about 40 days; and at 12-13°C, only 30 days.
The effective accumulated temperature required for most apple cultivars from the start of growth to flowering is 185±10°C, with differences of up to 101°C in some years. The accumulated temperature required differs among different cultivars, or for the same cultivar in different regions and years; different topography and microclimates also have an effect.
III. Apple tree flowering stage temperature:
For apples to flower, they first need to reach a certain amount of accumulated temperature. The apple flowering stage is sensitive to temperature. Temperature is an important limiting ecological factor for the successful completion of flowering, pollination, fertilization and fruit set. Generally, the suitable temperature during the apple flowering stage is 11.4-11.8°C, and the optimum temperature is 17-18°C. From the perspective of the temperature required for the activity of the pollination vector, bees, bees generally stop going out at below 10°C; between 15-29°C, they gradually become more active as the temperature rises, which is favorable for pollination and fertilization.
The flowering stage temperature is an important condition for apple pollen germination and pollen tube elongation in completing the fertilization process. According to observations, different cultivars require different suitable temperatures. The suitable temperature for pollen germination is generally between 10-25°C, with the optimum temperature being 15-20°C; above 30°C, pollen germination is obviously inhibited.
IV. Effect of spring low temperature on apple trees:
Spring low temperature: Because apple-producing areas in China mostly belong to a continental monsoon climate, spring temperatures are unstable and low temperatures often occur, with late frost damage being particularly common. In spring, apples are in the stages of bud break, flowering and fruit set, and have weak low-temperature tolerance and are sensitive to temperature.
Spring temperature is closely related to apple fruit shape and appearance quality. Research has shown that when the temperature is relatively low and the climate is cool 15-16 days after apple flowering, the fruit grows faster along the vertical axis than the horizontal axis, forming an elongated shape with a large fruit shape index.
V. Effect of summer and autumn temperatures on apple trees:
Because summer and autumn coincide with the period when apple shoots stop growing, flower buds differentiate, and fruits develop and mature, summer and autumn temperatures have a great influence on flower bud differentiation, yield formation and quality. Surveys suggest that in summer and autumn (June-September), excessively high or low temperatures are unfavorable to the above-mentioned growth processes of apples; a monthly average temperature range of 16.5-22.85°C is the most suitable.
If summer temperatures are too high, the ecological responses are: a smaller fruit shape index, poor coloring, fruit flesh that tends to become mealy, poor uniformity of ripening, reduced vitamin content, and poor fruit aroma, flavor and storability.
Summer temperature and flower bud differentiation: Research indicates that the suitable air temperature for the beginning and peak periods of apple flower bud differentiation is 20-27°C. The morphological differentiation stage of flower buds in Delicious and Ralls Janet begins after a certain number of days when the average temperature is stable above 20°C.
VI. Effect of winter low temperature on apple trees:
The entry of apples into true dormancy is mainly due to the effect of low temperature, and they are not very sensitive to conditions such as short daylight and dryness. Regarding ending the true dormancy of buds, many studies believe that cool winter climate is also necessary. Chilling hours: that is, the number of hours experiencing temperatures below 7.2°C. The starting point for calculating chilling is 7.2°C. Scholars in various countries now mostly use 7.2°C as the standard for accumulating hours. The CH value required by apples varies by cultivar, with large differences. As modern cultivation areas expand toward lower latitudes, the CH value required by apples generally tends to decrease. From the early requirement of 1400-3684°C to the recent requirement of 500-1700°C.
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