What is the development process of flower organs?

Plants mature before flowering, and then go through the induction stage of low temperature vernalization or photoperiod flowering, followed by flower bud differentiation. At this time, the apical meristem differentiates into flower primordium, and then develops into various organs of the flower from the flower primordium (Figure 2-20), and the flower bud opens under suitable conditions, which is called "flowering". After flowering for a certain number of days, the flowers finally fall and then transfer to the development of fruits and seeds.

After the induction of flowering, the process of flower organ development and flower opening and falling is more important for ornamental flowers.

As for the development of flower organs, this paper focuses on the conditions of flower organ development, physiological changes during development and gender differentiation of flowers.

1. Conditions of floral organ development

The conditions of flower organ formation and development are similar to those of inducing flower bud differentiation.

(1) lighting

After the floral organ begins to differentiate, strong light and long sunshine can promote the formation of floral organ, which may be related to the accumulation of photosynthetic products. The shading experiment of soybean shows that during the flower development, the stronger the light, the more flowers will be formed. Another example is that the greater the planting density of rice, the greater the floret degradation will be. Roses and peaches planted in a cool place don't bloom at all.

The development of floral organs in different plants requires different light intensities. Shade plants have lower requirements than sun plants, such as camellia and osmanthus, and have stronger tolerance to shade. But most cultivated plants belong to sun plants.

The formation of floral organs in many plants also needs a certain photoperiod. For example, Silene pendula can weaken the growth of petals and anthers at the same time under long sunshine conditions. This also shows that the factors that promote petal development usually affect anther development.

The development of floral organs of some diurnal neutral plants also needs proper photoperiod. For example, the woody hybrids of Verbenaceae have nothing to do with the photoperiod, but they have to go through at least 1 1 short sunshine period, and the dark period is more than 8 hours before they can blossom. Eggplant vegetables are short-lived plants. Because of long-term artificial cultivation, the requirement for sunshine is close to neutrality, so both spring sowing and autumn sowing can bloom, but when flowers develop, the hours and intensity of light can be appropriately extended, which can also promote the formation of flower organs.

During the development of floral organs, plants that require but cannot meet the photoperiod will produce deformed flowers. For example, Impatiens balsamina, a short-day plant, even after 90 short-day cycles under photoperiodic induction, if it is converted into a long-day condition, the tissues that have been transformed into flowers will still resume vegetative growth. It can be seen that there are one or several round structures in the inner layer of flowers, and they will return to the vegetative top, and the calyx and corolla formed will increase and have the shape of leaves. In the flowering process, once transformed into long-day conditions, the short-day plant Sophora flavescens will also produce the above-mentioned "nutritional flowers." In the experiment of inducing Xanthium sibiricum to flower, it was also found that when the induction dark period was insufficient, the development of flower organs would also slow down. Vegetables and plants have a similar situation. Chinese cabbage, for example, needs long sunshine after vernalization at low temperature. If it is still in short-term sunshine, plants will produce abnormal flowers or flowers will not be full.

(2) Temperature

The development of flower organs needs a certain temperature. The development of floral organs in different plants requires different temperatures.

Petunia, a short-lived plant, needs to be cultured at 28℃ for 10 hour after getting the dark period of 15 hour to complete the process of apical meristem forming flowers. However, if this temperature is maintained, the formation of flower organs will be inhibited and it will return to the vegetative growth state. Another example is the short-day treatment of autumn chrysanthemum in summer. If the plant is still in a high temperature state, the developing flower bud will become a vegetative bud.

Blaauw and others in the Netherlands think that tulip flowers have different requirements for temperature at different development stages. It can be divided into three different suitable temperature stages: 20℃, 8-9℃ and 23℃.

The same is true of the development of rice flowers. At high temperature, the differentiation process of young spike was obviously shortened, and at low temperature, the development was delayed or stopped. When the temperature is lower than 17-20℃, the normal development of sexual cells will be affected.

Some biennial vegetables that need low-temperature vernalization, such as Chinese cabbage and cabbage, can accelerate the formation of flower organs after flower bud differentiation begins, and long sunshine and high temperature (above 15-20℃) can promote bolting; However, if the temperature condition is not suitable, the flower organ will be stunted or stop developing halfway, or it may turn into a vegetative growth state. It is observed that the temperature above 65438 07℃ is needed for the formation of flower primordium of sweet pepper and tomato. When the temperature was 10- 15℃, the flower primordium was delayed by 12- 15 days. It is considered that the suitable temperature for flower bud differentiation, flowering and fruiting of Solanaceae vegetable plants requires a daily temperature of 20-25℃ and a night temperature of 5- 10℃, which is slightly lower than the daily temperature. When the temperature is higher or lower than this range, the flower bud differentiation is delayed, the number of flowers is reduced, and the flowers become smaller and fall off.

As shown in Figure 2-2 1, the temperature is very high during the day and at night, and the number of tomato inflorescences is greatly reduced. The daily temperature 15℃, the night temperature 10℃, and the inflorescence is flowery.

Fig. 2-2 1 Effect of temperature (day temperature-night temperature) on the number of flowers per inflorescence of tomato.

(Quoted from Li Shuxuan's Vegetable Cultivation Physiology)

Some plants have less strict requirements on temperature and light for their early maturity types and flower development. Therefore, it is more appropriate to choose early flowering and early maturing varieties when controlling the flowering period of plants or introducing and domesticating plants. (3) Cultivation conditions Cultivation and management conditions can affect the development of flower organs. Often, when nitrogen fertilizer is insufficient in the soil, the development of flowers is slow and the number of flowers decreases; Too much nitrogen fertilizer will cause white growth of branches and leaves and limit the development of flower organs. Therefore, in the process of flower formation, it is required that the soil contains appropriate amount of nitrogen fertilizer and appropriate amount of phosphorus and potassium fertilizer to ensure the normal development of flower organs.

As can be seen from Figure 2-22, increasing nitrogen, phosphorus and potassium has no obvious effect on leaf buds, but increasing phosphorus and potassium, especially phosphate fertilizer, can promote the occurrence of flower buds.

Fig. 2—Effects of 2—22N, P and K concentrations on the formation of peach blossom buds and leaf buds.

(Fukuda, Kondo, 1959)

Figure 2-23 shows the effects of applying nitrogen fertilizer at different stages on the development of apple flowers and young fruits. The experiment shows that applying nitrogen fertilizer can increase the number of flowers and young fruits, and the effect in summer is better than that in autumn and spring.

Fig. 2-23 Effects of nitrogen application at different stages on flowering and fruit drop of lambotte Ni apple trees.

(Quoted from Hill-Curtingham and Williams, 1967)

Soil moisture can also affect the development of flower organs. There is too much soil moisture, branches and leaves grow too vigorously, and the amount of flower bud differentiation is relatively reduced. When the soil is dry, the growth of plants is weak, the development of flower organs is delayed, and the amount of flowers is reduced. Therefore, in the cultivation management, it is necessary to maintain the appropriate water content in the soil.

From flower primordium to full bloom, serious water shortage will reduce the number of inflorescences at any time at this stage (Hartmann and Panetsos, 196 1). Therefore, in foreign countries, many seed orchards are irrigated after the trees have differentiated into flower buds (sweet, 1975).

Some plants, before and at the early stage of floral organ formation, properly control water, resulting in short-term drought, which is conducive to the occurrence and development of flower buds. For example, the drought before and at the beginning of litchi flowering can promote the formation of flower buds (Nahata and Suehisa, 1969). (4) The internal factors affecting the development of flower organs are the nutritional status and hormone level in plants.

The development of flower organs needs a certain amount of organic nutrients, which shows that the nutritional conditions and accumulation of nutrients in plants are very important. However, in the process of flower organ development, there is often a contradiction between the growth of branches and leaves and the development of flower organs, which is very prominent, especially for woody plants. Therefore, people attach great importance to adjusting the balance between the two in production. However, the vegetative growth of most biennial herbs has basically ended after flowering, so this situation does not exist. As long as the original green leaf area of plants is kept as much as possible, the leaves are prevented from premature aging and withering, and the photosynthetic products can continue to supply the development of flowers, so that the normal growth and development relationship can be maintained.

The experiment of Jiangkou et al. (1958) on solanaceous vegetables in Japan proved that more flower buds can be formed when plants contain higher carbohydrate, especially higher total sugar and nitrogen compounds.

The flower bud differentiation of plants is closely related to the hormone level in vivo. According to the experiment, the content of auxin was low before flower bud differentiation, and the level of auxin increased significantly from flower bud differentiation to flowering. For example, if someone takes a flower bud of Dianthus and cultivates it on a comprehensive medium containing a series of growth regulators, it is found that the growth of this plant calyx needs GA.

It is also found that the extract of carnation flowers contains GA, and when GA is artificially applied to carnation, the petals can become larger. Some people also found auxin in citrus petals, and saw that the growth of citrus petals is determined by the content of auxin. GA was also found in chrysanthemum extract, but artificial use of chrysanthemum auxin would inhibit the formation of chrysanthemum flower organs. This shows that different kinds of hormones have different reactions to various plants.

Hackett and Sacha( 1968) used GA in leafy flowers, which prevented the development of inflorescences. However, the use of growth inhibitor CCC promoted the development of inflorescence.

As can be seen from Figure 2-24, B9 and: HM can promote the formation of flower buds, while GA has little effect on the growth of new shoots.

Fig. 2-24 Effects of different concentrations of growth regulators on shoot elongation and flower bud formation of two-year-old Stark earliest apple (concentration ppm).

(Lukewell, 1970)

2. Physiological changes of floral organ development

In the process of flower bud differentiation, the growth cone in the bud changes from vegetative meristem to reproductive meristem, forming the physiological state of dioecious plants in a short time, and the physiological changes in this process should be very significant.

At present, people know little about the complexity and particularity of cell metabolism in different parts of flower organs and the physiological differences between males and females. However, we can know that during this period, the metabolism of flower organs is very active, and nutrients, water, mineral elements and hormones are continuously transported to developing flowers. From the girdling experiment of osmanthus fragrans, the author found that interrupting the supply of plant organic nutrients at the initial stage of flower bud differentiation can prevent the formation of flower buds.

According to most reports, flower bud formation depends on the information transmission related to the metabolic process of DNA→RNA→ protein. 3. Sex differentiation of flowers Most plants have calyx and corolla. Stamens and pistils are important parts of flowers that really reproduce the next generation. Most plants are bisexual flowers, such as most Rosaceae plants and some flower plants. But quite a few plants are unisexual flowers, which are planted on the same plant, such as perennial begonia, bulbous begonia, cucumber, beech and other plants. Other plants have male flowers and female flowers, but they don't grow on the same plant, and there are "female plants" and "male plants", such as willow, bayberry and holly.

This diversity of plants in nature provides a broad prospect for human beings to make full use of plant resources. Such as marijuana, there are male and female plants. In order to improve the quality of fiber, male plants must be selected. Another example is that in order to increase the yield of cucumber, measures should be taken to reduce the number of male flowers and increase the number of female flowers. Among flower plants, some flowers are big and bright, and most of them are bisexual.

Based on the different requirements in production and cultivation, it is very important for people to identify the sex of plants in the early stage of plant growth and how to control the sex artificially. This is the discussion of gender physiology.

According to a large number of research results, the gender changes in the flowering process of plants are also regular.

(1) Flower appearance procedure

It has been noticed that in monoecious plants, the sex of flowers appears in a certain order. Male flowers often appear first, then male flowers and bisexual flowers, and finally only female flowers appear.

On branches at all levels, the occurrence procedure of sex is that the proportion of female flowers increases with the increase of branches. These conditions seem to indicate that female flowers will only appear when the flowering period of plants is high.

(2) The influence of environmental conditions on flower sex.

① Lighting

In 19 1 1, Turnoyes noticed that the length of sunshine can cause the sex differentiation of flowers. For example, the long-day plant dwarf snow wheel can increase the number of female flowers through long-day treatment.

Some people think that under normal circumstances, short-day plants can produce more female flowers (such as hemp), while long-day plants can produce more male flowers. Long sunshine can promote long-day plants to have more female flowers (such as spinach) and short-day plants to have more male flowers. So is the short-term formation of gourd. The number of female flowers of cucurbitaceae plants can increase under the conditions of short sunshine and low temperature before flowering, but under the conditions of long sunshine and high temperature, the number of female flowers appears later and the node position of female flowers is higher than before.

However, there are also opposite situations, such as the hybrid of short-lived begonia, where the proportion of female flowers increases under long sunshine and high temperature (Table 2-5). Another example is the short-day plant chrysanthemum, whose female flowers and bisexual flowers are in the same inflorescence, and the periphery is female flowers, but long sunshine can increase the number of female flowers. Therefore, whenever the flowering period of chrysanthemum is too late, due to the short sunshine, it often forms a disk with fewer flowers around it, which affects the appearance. It can be satisfied by artificially supplementing the sunshine for a long time.

On the other hand, some plants tend to increase the number of female flowers when increasing the number of photoperiodic induction, but when the photoperiodic induction is insufficient, it will increase the number of male flowers.

Although the length of light is not very clear about the mechanism of flower sex formation, the factors that determine flower sex formation are determined by the genetic characteristics of plants themselves, and the influence of photoperiod only plays a secondary role, which is different from the requirements for flower formation in photoperiodic induction. ② The temperature conditions in the process of flower formation will also affect the formation of flower sex.

The length of light can determine the generation of flower buds, and the temperature can determine the gender trend of flower buds, especially the low temperature at night, which is very useful. The experiment of melons shows that the requirement of female flowers for low temperature is more urgent than short sunshine, especially the night temperature at that time, which has the greatest influence. When the temperature is low at night, it is more conducive to the differentiation of female flowers.

Table 2-5 Effects of Temperature and Sunshine Length on Sex Expression of Begonia Flower

(Quoted from Plant Physiology of Beijing Forestry College 198 1)

The author observed the flower bud differentiation of litchi, and found that the optimum temperature for the differentiation period was 0- 10℃. In the low temperature period of 1 and February, the male flowers formed first, while the female flowers formed at the lowest temperature.

However, in other dioecious plants, the situation is different. Warm conditions are conducive to the formation of female flowers, while low temperature is conducive to the formation of male flowers. ③ Other factors that control the sex of flowers, such as cultivation conditions, gas composition and plant growth regulators, can control the sex of flowers, and some of them are very sensitive to the influence of sex.

Some unsaturated gases, such as ethylene, acetylene and carbon monoxide, are used to treat plants, which can increase the number of female flowers in some plants. Treating cucumber with carbon monoxide can obviously increase the proportion of female flowers (Figure 2-25).

As can be seen from the figure, the female flowers in the control plants appear very late, and the number of female flowers is very small; CO treatment made female flowers appear in advance and the number increased greatly.

It is also found that some plant hormones and synthetic growth regulators also have obvious effects on plant sex differentiation. If IAA, NAA and other auxins are used, the number of female flowers in cucumber can be increased and the node position of female flowers can be reduced. CCC can promote feminization, TIBA (triiodobenzoic acid) and MH can inhibit the appearance of female flowers, and GA can also inhibit the differentiation of female flowers.

Fig. 2 —— Effect of 25Co treatment on the order of male and female flowers in cucumber.

The abscissa is the date, and the ordinate is the number of female flowers and male flowers (♂ male flowers, ♀ female flowers) on the inspection date.

(Quoted from Plant Physiology by Cao Zongxun and Wu Xiangyu)

It can also be speculated that there should be genes in charge of female flowers and male flowers respectively in gender differentiation. These genes can be turned on or off under certain conditions. It is also possible that the changes of some hormone components or their proportions in plants can affect the expression of sex genes through some internal channels.

In addition, the status of soil fertility and water will also affect the sex of flowers. Generally, under the condition of sufficient nitrogen fertilizer and water supply in the soil, the development of female flowers can be promoted.

In addition, phosphorus, boron, potassium and other elements can also improve the female flower rate of melon.

According to мтястребоосиалешина, take cucumber as an example. In alkaline soil, the proportion of female flowers increased to1.8-4.4; In acidic soil, the proportion of female flowers is high, reaching 1.4-7.0, and the flowering period is the latest.