How does temperature affect the growth and development of flowers?
Many foliage plants can only live in medium to high temperature environments; if kept at low temperatures, they will suffer cold damage or even die. For example, Alocasia lowii has an optimum temperature of 20-30°C, and the indoor temperature in winter must not be lower than 18°C; Codiaeum variegatum (croton) drops its leaves when exposed to cold, and ferns also dislike low temperatures. Plants of the genus Maranta are the most intolerant of low temperatures: once the ambient temperature falls below 15°C, the leaves will shrivel, curl, and eventually drop off. Therefore, if the indoor temperature in winter is below 15°C, you need to be careful when choosing foliage plants.
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1. Temperature affects the developmental state of flowers
Temperature not only affects the geographical distribution of flower species, but also affects every process and stage of the growth and development of various flowers. For example, the dormancy of seeds or bulbs, stem elongation, and the differentiation and development of flower buds are all closely related to temperature. Different developmental stages of the same flower have different temperature requirements; that is, from seed germination to seed maturity, the temperature requirements constantly change. Take annual flowers: seed germination can take place at relatively high temperatures, the seedling stage requires lower temperatures, but as the seedlings gradually grow to the flowering and fruiting stage, the temperature requirements gradually increase. The seeds of biennial flowers germinate at relatively low temperatures, and the temperature required during the seedling stage is even lower, otherwise they cannot successfully pass through the vernalization stage; when flowering and fruiting, they require a temperature slightly higher than that of the vegetative growth period. Low temperature is also the key to breaking the dormancy period of many seeds. For example, seeds of Trollius chinensis collected on the summit of Baihua Mountain at an altitude of 1800 m, sown in the open ground in Beijing at normal temperature, rarely germinate; after low-temperature treatment, the germination rate can reach more than 60%.
2. Temperature affects the nutrient accumulation of flowers
High daytime temperatures favor photosynthesis to form carbohydrates; low nighttime temperatures help inhibit the breakdown of carbohydrates by respiration. Suitable day-night temperature difference: tropical plants, 3-6°C; temperate plants, 5-7°C; desert plants, more than 10°C.
3. Temperature affects flower bud differentiation and flowering
Some plants must carry out flower bud differentiation under conditions where the air temperature is higher than 25°C, and after a certain period of low temperature to break dormancy, they flower. Such as rhododendron, camellia, plum, gladiolus, tuberose, and canna. Some plants need to carry out flower bud differentiation at relatively low or low temperatures. Such as autumn-sown herbaceous flowers like Calendula officinalis and Bellis perennis.
4. Temperature affects flower color
Many flowers become paler in color as temperature rises and light intensity weakens. For example, Chinese rose and dahlia grown under high temperature conditions become paler in color, and become more vivid in cool places.
5. The effects of extreme temperatures
Extreme high temperatures and extreme low temperatures can cause plant death. Sudden high and low temperatures also have a great impact on the growth and development of flowers; temperatures that are too high or too low will cause flowers to be damaged or die.
II. The effect of temperature on the distribution of flowers
1. Cold regions mainly have cold-hardy flowers distributed in them. These flowers have strong cold resistance and can tolerate low temperatures above 0°C, and some of them can tolerate low temperatures of -5°C to -10°C and below, and can overwinter in the open ground in Beijing. Such as Viola tricolor.
2. Tropical and subtropical native cold-tender flowers. These flowers cannot endure low temperatures of 5-0°C and need to be cultivated in greenhouses in the north. Such as tropical orchids and Codiaeum variegatum.
3. Temperate regions native semi-cold-hardy flowers. This type of flower mostly originates from the warmer parts of the temperate zone, and its cold resistance is between that of cold-hardy and cold-tender flowers; in the north, winter protection is needed to survive the winter.