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The resistance of plants is related to many factors, such as:

Different species of plants have different resistance (related to the living environment).

Different varieties or types of the same plant can show great differences in resistance

The drought resistance of different growth stages is also different (the flowering stage is particularly sensitive to drought, followed by the seed abundance stage).

The larger the root-shoot ratio, the stronger the drought resistance (more efficient use of soil moisture) [use dry weight, milligrams for roots, grams for aerial parts].

The larger the proportion of bound water in the cells, the stronger the drought resistance, and the smaller the leaf cells (which can reduce the mechanical damage caused by the cells).

The leaf veins are dense, and the number of stomata per unit area is large (strengthens transpiration and is conducive to water absorption).

The permeability of the cell fluid is low (resistance to excessive dehydration).

In the case of water stomata closes later, photosynthesis does not stop immediately and the synthetic activity of enzymes still prevails (a certain level of physiological activity is still maintained, synthesis is greater than decomposition).

Anyway, that's what my book says, and we haven't talked about this part yet, and some of them don't really understand, I hope it will be helpful to you, and I won't waste my time typing the keyboard in vain. Hope.

The drought resistance of plants is related to the characteristics of their varieties. For example, cacti are very resistant to drought.

Different species look at genes, and the same species looks at the growth stage and the proportion of bound water.

The quality characteristics of drought-tolerant plants are:1. The root system is well developed and stretches deep underground, which is to absorb the water from the deep underground;

2. Secondly, there are generally no branches, the leaf shape is generally needle-shaped, reducing the evaporation area, some are leaves but generally have little or no stomata on the front of their leaves, which is to reduce the transpiration of water;

3. Such plants generally grow close to the ground, and the height is very low, but the coverage area may be large;

4. Some drought-resistant plants can obtain surface water through the stomata on the back of the leaves.

What are the common drought-resistant plants:

1. Cactus: The native land is mostly desert and likes high temperature and arid climate;

2. Aloe vera: Native to tropical Africa, with little rain and a harsh local environment, the plant has a drought-tolerant characteristic;

3. Agave: likes warm, dry and sunny environment, slightly cold-tolerant, more shade-tolerant, and drought-tolerant;

4. Lover's tears: Native to southern Africa, widely cultivated all over the world, its nature likes a warm and humid, semi-shady environment, it has strong adaptability, and is more drought tolerant and cold-resistant;

5. Hexi chrysanthemum: born in sandy land, sandy edge, lowland between sand dunes, Gobi gully and sandy field edge.

This is the plant in order to adapt to the surrounding environment, in order to survive. Self-protection measures against the external environment are the result of long-term evolution of plants. One protection of drought-tolerant plants is to close the stomata to reduce transpiration and reduce water loss.

Some books are cold and have fallen leaves, or the pages are leathery or waxy, and so on.

Objective] The objective of this study is to study the relationship between cold resistance and drought resistance of winter rapeseed and the relationship between cold resistance and drought resistance, so as to provide a reference method and theoretical basis for the improvement of winter rapeseed and the comprehensive evaluation of cold resistance and drought resistance in northern China.

Method】 Six samples of winter rapeseed with different cold resistance grades were simulated under low temperature and drought stress by natural cooling treatment (15 —-5) and artificial water control method (drought stress and 10 d), and the changes of morphology, physiology, biochemistry and growth indexes were analyzed, and the cold resistance and drought resistance of different varieties were comprehensively evaluated by membership function method, correlation analysis method, cluster analysis method and principal component analysis method.

Result】 The overwintering rates of the six winter rapeseed varieties were very different (. The botanical morphological characteristics of cold-tolerant varieties were as follows: seedlings creeping close to the ground, the growth point was depression below the ground surface, the leaf color was dark green, and the true leaf thorns were many. After low temperature stress, the physiological and biochemical indexes of cold resistance changed significantly, the relative conductivity and MDA (malondialdehyde) content increased, and the increase of cold resistance varieties was small. The activities of SOD, POD and CAT enzymes increased, and the contents of soluble protein, soluble sugar, free proline and other regulatory substances increased significantly, and the varieties with strong cold resistance changed significantly and had significant differences.

With the prolongation of drought stress, the membrane structure was first destroyed, the relative conductivity and MDA content increased, the cells lost water, the relative water content of leaves, the content of free water and chlorophyll decreased (photosynthesis decreased), the seedling length, leaf and root fresh dry weight decreased until the seedlings wilted, and the change range of the varieties with strong drought resistance was small, and the leaves of the varieties with strong drought resistance had strong water retention capacity, less soil water consumption and small wilting coefficient. According to principal component analysis, the cold resistance of the six winter rapeseed was Longyou 7, Longyou 6, Longyou 9, Yanyou 2, Tianyou 2, and Tianyou 2, while the drought resistance was Longyou 6, Longyou 7, Longyou 9, Yanyou 2, and Tianyou 2.

Conclusion】 The cold resistance and drought resistance of different winter rape varieties are quite different due to the coexistence of low temperature and drought in the cold and arid areas of northern China.

This is the result of long-term evolution of plants, which are resistant to drought because some plants have developed root systems or reduce water evaporation, and the same is true for cold resistance.

When the outside temperature decreases, the dissolution of soluble substances such as sugars will occur strongly in the somatic cells of plants, increasing the concentration of cell juice.

The mechanism of drought resistance of plants is as follows:

Worldwide, arid and semi-arid regions cover more than 30 per cent of the total land area; In China, the arid and semi-arid regions account for about 50% of the country's land area, and most of them are distributed in the northern and northwest regions.

Therefore, drought is the main limiting factor for agricultural production in this region. If we add the impact of seasonal drought in other non-arid areas, the impact of early drought on agricultural production will be more serious, so from the perspective of plants, how to improve plants has become an important drought resistance research topic for the future development of dryland agriculture.

Drought damage: Damage caused by water deficit in plants due to drought. Early dry is a climatic phenomenon in which soil moisture is lacking and the air is dry due to long-term lack of rain or little rainfall.

In terms of drought resistance, drought is a soil or climate phenomenon in which the soil is left unwatered or the air is dry. Drought has two meanings in meteorology, one is arid climate, that is, the basic situation of the climate in arid and semi-arid areas; The second is the abnormal climate, and the precipitation in a certain period of time is much less than the average for many years.

The moisture status of crops depends on both absorption and transpiration, with water deficit caused by reduced water uptake or excessive transpiration. Therefore, in the study of drought resistance physiology, according to the place where drought occurs and the country of origin, it can be regarded as the phenomenon that the industry has produced soil drought and atmospheric drought physiology, which is suspected to have invaded plants and difficulty in absorbing water, resulting in water deficiency in the body.

Here's how to improve the drought resistance of plants:

1. Breeding drought-resistant varieties. It belongs to the category of breeding science and is also a basic measure to improve the drought resistance of crops.

2. Drought resistance exercise. Crops are artificially subjected to drought conditions that are sub-lethal to starvation, so that crops can withstand drought and improve their ability to adapt to drought. In agricultural production, many effective drought-resistant exercise methods have been refined, such as "squatting seedlings"."Shelving seedlings","Hungry seedlings"."Double bud method" and so on.

Squatting seedlings"It refers to the proper control of water in the seedling stage of crops to inhibit their growth. ""Seedling" means that the vegetables are pulled up before cutting, and then planted after they are properly wilted for a period of time. "Russian seedlings"It refers to some cuttings of vine seedlings, which are not cut immediately after being cut from the mother, but placed in the shade for 1-3 days or even longer, and then planted.

The double-bud method refers to the seed exercise before sowing, such as letting the grain seeds absorb water first, and then air drying, so repeated 2-3 times, and then sowing, which can effectively improve its adaptability to dry early.

3. Deep turning of the soil, combined with deep turning and increasing the application of high-quality organic fertilizer, is conducive to the development of the root system and the rooting.

4. Scientific and rational application of chemical fertilizers. On the basis of the appropriate amount of nitrogen fertilizer, the application of phosphorus and potassium fertilizer can improve the drought resistance of crops"The purpose of "using fertilizer to transfer water" is to improve the dual utilization rate of water and fertilizer.

5. Application of anti-transpiration agent. The application of anti-transpiration agent has been studied and explored, and its mode of action is mainly the following two ways, one is the water dispersion loss of the yang broken plant body, the second is to improve the reflection of canopy light energy to reduce the energy used for foliar transpiration, and the third is to control the opening of stomata.

Abbreviated as drought-tolerant plants, i.e., "water-changing plants".

Therefore, when this kind of plant loses water in the drought, the whole plant is in an air-dried state and does not die (just dormant), so it is called drought-tolerant plants or drought-tolerant plants.

Mainly lower plants and mosses. Such as many algae, lichens, purple calyxes. The main vascular plants are vesicular mosses (Carex physodes), curly cypress and a few flowering plants growing on rock walls.

Some plants native to the temperate or cold zone have strong cold resistance, and can overwinter below 0 in winter are called cold-tolerant plants.

Drought-resistant plants, such as cacti, meet the needs of the dry season by storing their own water during periods of abundant rainfall.

The most direct impact of drought on plants is to cause protoplasm dehydration, which is the core of drought damage, which can cause a series of injuries, mainly as follows:

1) Change the structure and permeability of the membrane The cell membrane loses its semi-permeability under drought damage, causing the extravasation of intracellular amino acids and carbohydrates.

2) Disrupt normal metabolic processes e.g., photosynthesis significantly decreases or even stops; Respiration is enhanced by water shortage, which decouples oxidative phosphorylation and decouples, and energy is mostly consumed in the form of heat, but there are also water shortages that weaken respiration, which affects the normal biosynthesis process; Protein decomposition is strengthened, the protein synthesis process is weakened, and proline accumulates in large quantities; Nucleic acid metabolism is disrupted, and drought can reduce the content of DNA and RNA in plants. Drought can cause changes in plant hormones, most notably an increase in ABA levels.

3) Abnormal distribution of water In times of drought, young leaves generally absorb water from old leaves, which causes old leaves to wither and die. The functional leaves with strong transpiration take water from meristem and other young tissues, causing some young tissues to lose water seriously and develop poorly.

4) Mechanical damage to protoplasts During drought, cells are dehydrated and shrink inward, damaging the structure of protoplasts, such as sudden rehydration, causing the uncoordinated expansion of the cytoplasm and the wall, tearing the protoplasmic membrane, and leading to the death of cells, tissues, organs and even plants.

Measures to improve drought resistance:

The breeding of drought-resistant varieties is the most fundamental way to improve the drought resistance of crops, and the following measures can also be taken to improve the drought resistance of plants

1. Drought resistance exercise: Moderate drought treatment should be carried out at the seed germination stage or seedling stage, so that the plants can undergo corresponding changes in physiology and metabolism and enhance their ability to adapt to drought. In the cultivation of crops, farmers use the "squatting seedling" method to improve the drought resistance of crops, that is, to give moderate water shortage treatment at the seedling stage of crops to inhibit the growth of aboveground parts, so as to exercise their ability to adapt to drought.

2. Rational fertilization Rational application of phosphorus and potassium fertilizers and proper control of nitrogen fertilizers can improve the drought resistance of plants. Phosphorus promotes the synthesis of organophosphorus compounds, improves the hydration of protoplasms, and enhances drought resistance. Potassium can improve carbohydrate metabolism in crops, reduce the osmotic potential of cells, promote stomatal opening, and facilitate photosynthesis.

3. Application of growth retardants and anti-transpirants In recent years, the application of growth retardants to improve the drought resistance of plants has achieved certain results.

4. Water saving, water harvesting, and the development of dry farming Dry farming refers to agricultural production technology that is less dependent on irrigation, and its main measures are to collect and preserve rainwater for later use, use different root zones to alternately irrigate, use fertilizer to transfer water, improve water use efficiency, use plastic film to cover and conserve moisture, grasp the law of crop water demand, and use water rationally.

For drought, it depends on the degree. The so-called drought refers to the phenomenon of water deficiency in the plant body, the leaves of the plant will droop, if the water is not in time, wilting will occur, if the drought is severe, the plant is easy to die because of the formation of permanent wilting. Of course, a small degree of drought is a manifestation of transpiration, forming a transpiration pull, which plays an important role in the transport of organic matter and water in the plant body, and promotes the growth of the aboveground part, that is, the so-called crown ratio increase.

Measures:1Drought resistance exercises for plants, i.e., keeping plants in a certain arid soil, will gradually adapt and develop resistance to drought 2The application of phosphorus and potassium fertilizers, and the application of less nitrogen fertilizers, will promote the development of the root system of plants and enhance the absorption of water.

The similarities and differences in the absorption of water and mineral elements by plant cells are mainly as follows:

1 There is a clear difference between the two.

One is the different mode of absorption: root cells absorb water by osmosis and diffusion, while mineral element ions are absorbed by active transport.

Second, the absorption power is different: the driving force for water absorption is the osmotic pressure composed of the transpiration pull force and the difference in solution concentration between the root cell and the environment; The driving force for the absorption of mineral element ions is mainly ATP produced by root cell respiration, and the carrier consumes energy to do work.

Third, the relationship between the amount of absorption and the external concentration is different: whether it can absorb water from the outside is determined by the relative concentration of the cell fluid and the external solution, when the concentration of the cell fluid is higher than the concentration of the external solution, the cell will absorb water, and vice versa, it will lose water; The amount of mineral element ions absorbed is determined by the type and number of carriers on the cell membrane.

2 The two absorption processes are closely linked and inseparable.

First, the absorptive organs are the same, that is, the main organs of resorption are all roots, and the most active parts are the cells (epidermal cells) in the mature zone

Second, mineral element ions are generally dissolved in water in an ionic state and absorbed in an ionic state; Moreover, after the mineral element ions enter the plant body, they are also transported to various organs and tissues of the plant body along with water.

Third, after the mineral element ions are absorbed by the cell, it will affect the concentration of the solution inside and outside the cell, thereby affecting the water absorption of the root cell. Therefore, the absorption of mineral element ions by roots and the absorption of water are two relatively independent physiological processes.

Plant cells are selective for ion absorption:

Its cytological basis is that there are specific ionophores on the membrane, and the types and quantities of ionophores on different plant cells are different, so the types and rates of ions absorbed are different.