Apple's physiological activities, biochemical reactions, and growth and development all depend on specific temperature conditions. Without the right thermal environment, apple trees may experience suppressed growth, developmental blockage, damage, or even death. Temperature plays a crucial role in regulating various life processes of apples, affecting their overall health, yield, and fruit quality.
The impact of temperature on apple growth is primarily reflected in several key aspects:
1) **Three-Point Temperatures**: Apple growth requires a minimum, optimal, and maximum temperature for its physiological processes. Generally, the minimum temperature is around 5°C, the optimal range is between 13–25°C, and the maximum is approximately 40°C. These values can vary depending on the variety, organ type, plant age, growth stage, and environmental conditions. Different species also have varying optimal average temperatures during the growing season.
2) **Accumulated Temperature**: Each apple variety, organ, and growth phase requires a certain amount of accumulated heat. This accumulated temperature significantly affects growth, development, yield, and fruit quality. It is often used as an indicator for variety characteristics and plays a key role in phenological forecasts, yield analysis, and ecological zoning.
3) **Accumulated Temperature Before Flowering**: Predicting the flowering period of apple trees often involves measuring effective accumulated temperature above 5°C. On average, it takes about 160–180°C to reach the initial flowering stage. However, the length of the flowering period varies with temperature—around 50 days at 7–8°C, 30 days at 12–13°C, and just 10 days at 40°C. The effective accumulated temperature required for most apple varieties to flower is about 185°C, though this can vary by up to 10°C between years or regions.
4) **Flowering Temperature**: Apple flowering depends on reaching a certain accumulated temperature. The ideal temperature for flowering is between 11.4–11.8°C, while pollination is most effective at 17–18°C. Bees, which are essential for pollination, become active only when temperatures rise above 10°C. Pollen germination also requires specific temperatures, typically between 10–25°C, with the best range being 15–20°C. Above 30°C, pollen germination is significantly reduced.
5) **Spring Temperature**: In spring, apple trees are in critical stages such as bud development, flowering, and fruit set. Sudden cold snaps or late frosts can be very harmful. Spring temperatures also influence fruit shape and appearance. Studies show that cooler temperatures after flowering can lead to longer fruits with higher shape indices, while warmer conditions result in shorter, rounder fruits.
6) **Summer and Autumn Temperatures**: These seasons are crucial for shoot cessation, flower bud differentiation, and fruit maturation. Summer and autumn temperatures greatly affect yield and fruit quality. Temperatures between 16.5–22.85°C are generally favorable. For example, high-quality apples from areas like Maoxian and Tianshui in Gansu Province are associated with summer temperatures ranging from 16.2–22.7°C. High summer temperatures can reduce fruit shape index, cause poor coloring, lower flesh firmness, and decrease vitamin content and flavor.
7) **Winter Chilling Requirement**: Apple trees require a certain number of chilling hours (hours below 7.2°C) to break dormancy. This requirement varies by variety, with modern cultivars needing fewer chilling hours due to shifting cultivation zones. Early varieties needed 1400–3684 chilling hours, but recent ones often require only 500–1700 hours. This adaptation helps apples thrive in lower latitude regions.
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Blood pressure reduction can be broadly divided into the following categories:
1. Diuretics:
Diuretics reduce blood volume by increasing the kidneys' excretion of sodium and water, thereby reducing the amount of fluid in the circulatory system. This helps reduce the pressure on the walls of blood vessels, resulting in lower blood pressure. Common diuretics include hydrochlorothiazide and indapamide. When using diuretics, it is necessary to be aware of possible side effects such as electrolyte disturbance.
2. Beta-blockers:
These drugs work by binding to the heart's beta receptors, reducing heart rate and myocardial contractility, and reducing cardiac output. At the same time, they also reduce sympathetic nerve activity, causing blood vessels to dilate, thereby lowering blood pressure. Common beta-blockers are metoprolol, bisoprolol, and so on. However, in some cases, such as patients with severe chronic obstructive pulmonary disease or asthma, it should be used with caution.
3. Calcium channel blockers:
Calcium channel blockers inhibit the contraction of vascular smooth muscle by preventing the influx of calcium ions in vascular smooth muscle cells, to dilate blood vessels and reduce peripheral vascular resistance, thereby reducing blood pressure. Nifedipine and amlodipine are common calcium channel blockers. They also have a certain dilating effect on coronary arteries and can improve blood supply to the heart muscle.
4. Angiotensin-converting enzyme inhibitors (ACEI) and angiotensin II receptor antagonists (ARBs) :
ACEI can inhibit the activity of angiotensin-converting enzyme and reduce the production of angiotensin II, thereby dilating blood vessels and lowering blood pressure. At the same time, they also have a certain protective effect on the heart and kidneys. Common ACEI are captopril, enalapril and so on.
ARBs play an antihypertensive role by blocking the binding of angiotensin II to receptors. This class of drugs has similar antihypertensive effects and organ protection to ACE but may be better tolerated in some patients. Common ARBs include valsartan, irbesartan and so on.
5. Alpha blockers:
Alpha-blockers work primarily by blocking alpha receptors on the smooth muscle of blood vessels, causing blood vessels to dilate and reducing peripheral resistance, thereby lowering blood pressure. This class of drugs is mainly used to treat high blood pressure caused by prostate hyperplasia but is relatively rarely used when used alone to lower blood pressure.
It should be noted that different types of blood pressure-lowering drugs have their specific indications and contraindications, and should be individually selected and adjusted according to the specific situation of the patient when using, while closely monitoring blood pressure changes and side effects of the drug.
Diuretics reduce blood volume by increasing the kidneys' excretion of sodium and water, thereby reducing the amount of fluid in the circulatory system. This helps reduce the pressure on the walls of blood vessels, resulting in lower blood pressure. Common diuretics include hydrochlorothiazide and indapamide. When using diuretics, it is necessary to be aware of possible side effects such as electrolyte disturbance.
2. Beta-blockers:
These drugs work by binding to the heart's beta receptors, reducing heart rate and myocardial contractility, and reducing cardiac output. At the same time, they also reduce sympathetic nerve activity, causing blood vessels to dilate, thereby lowering blood pressure. Common beta-blockers are metoprolol, bisoprolol, and so on. However, in some cases, such as patients with severe chronic obstructive pulmonary disease or asthma, it should be used with caution.
3. Calcium channel blockers:
Calcium channel blockers inhibit the contraction of vascular smooth muscle by preventing the influx of calcium ions in vascular smooth muscle cells, to dilate blood vessels and reduce peripheral vascular resistance, thereby reducing blood pressure. Nifedipine and amlodipine are common calcium channel blockers. They also have a certain dilating effect on coronary arteries and can improve blood supply to the heart muscle.
4. Angiotensin-converting enzyme inhibitors (ACEI) and angiotensin II receptor antagonists (ARBs) :
ACEI can inhibit the activity of angiotensin-converting enzyme and reduce the production of angiotensin II, thereby dilating blood vessels and lowering blood pressure. At the same time, they also have a certain protective effect on the heart and kidneys. Common ACEI are captopril, enalapril and so on.
ARBs play an antihypertensive role by blocking the binding of angiotensin II to receptors. This class of drugs has similar antihypertensive effects and organ protection to ACE but may be better tolerated in some patients. Common ARBs include valsartan, irbesartan and so on.
5. Alpha blockers:
Alpha-blockers work primarily by blocking alpha receptors on the smooth muscle of blood vessels, causing blood vessels to dilate and reducing peripheral resistance, thereby lowering blood pressure. This class of drugs is mainly used to treat high blood pressure caused by prostate hyperplasia but is relatively rarely used when used alone to lower blood pressure.
It should be noted that different types of blood pressure-lowering drugs have their specific indications and contraindications, and should be individually selected and adjusted according to the specific situation of the patient when using, while closely monitoring blood pressure changes and side effects of the drug.
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