Literary Dictionary History
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Phoenix bamboo is a variety of grass in the family Poaceae, the genus Filial Bamboo. Phoenix bamboo is loved for its beautiful and unique form, emerald green and fresh charm. In recent years, due to the needs of urban greening, phoenix bamboo has been introduced into the city as an ornamental bamboo in large quantities.
Salt stress is an ecological term published in 2006 that refers to the hyperpermeability of plants due to the high salinity environment in which they grow. Biologically, salt dilution will cause an imbalance in plant ion concentration, thereby affecting plant growth and development.
With the warming of the global climate, soil salinization will become more and more serious, which will lead to the impact of salinity stress on anchovy bamboo more and more significant.
Therefore, this has caused great difficulties for people to grow phoenix bamboo, and now salt stress is a common abiotic stress in nature, which seriously affects the growth of plants and reduces the yield of crops.
Moreover, the salt resistance mechanism of plants is very complex, involving the tolerance of plant stress. Moreover, after the growth process of phoenix bamboo is stressed by salt, the internal physiological mechanism response is also a rather cumbersome and complex process.
Therefore, the meaning of salt stress includes both water stress and salt ion stress, and how to reduce the harm caused by salt stress to phoenix bamboo and minimize the loss requires us to conduct many experiments and discussions.
This paper mainly describes the effects of salt stress on the growth and physiological characteristics of Bamboo anchovy, hoping to provide a new perspective for solving the problem of salt stress.
Physiological characteristics of phoenix bamboo
Phoenix bamboo prefers warm and moist soil, it is very cold tolerant, not afraid of strong light, and is mainly cultivated in the southern regions of the mainland.
In addition, the leaves of Phoenix bamboo are evergreen, the growth cycle is short, the plant is generally 3-4m tall, and the vitality is tenacious, whether it is in a strong light environment or rainy weather.
However, although the stress tolerance of Bamboo is strong, salt stress will lead to high salt content and PH value in the soil, which will indirectly affect the growth of Bamboo anchovy.
It should be noted that the experiment of "measuring the effect of salt stress on anchovy" mainly includes three aspects: the determination of the diurnal change of photosynthetic rate, the determination of chlorophyll content, and the determination of nitrate reductase (NR) activity.
Here, we first briefly describe the concepts of photosynthetic rate, chlorophyll and nitric acid.
Photosynthesis usually refers to the process by which plants absorb light energy, process carbon dioxide in the air and water from nature into organic matter, and release oxygen.
And the photosynthesis of plants often changes with the changes of the external environment, and the condition of the plants themselves also affects the strength of photosynthesis.
Light changes with climate changes throughout the year, for example, summer is the most sunny, so summer is the strongest stage of plant photosynthesis, vegetation is luxuriant, grass and trees grow.
Winter directly hits the Tropic of Capricorn, and winter has the shortest days and longest nights in the four seasons, so winter is the weakest stage of plant photosynthesis, and most plants are dormant.
Light also exhibits circadian rhythm changes throughout the day. The diurnal variation law of photosynthesis is shown by the measurement of the diurnal variation of photosynthetic rate.
The photosynthetic rate reflects the speed of the accumulation capacity of plant organic matter, and plays an extremely important role in the growth rate and morphological appearance of plants.
Leaf green content is an important indicator to guide crop cultivation and growth and selection of crop varieties, reflecting the size of plant net photosynthetic rate, and plant leaf green content is positively correlated with plant net photosynthetic rate.
During the growth process, plants need a large amount of nitrogen to supply for the synthesis of organic matter such as protein. The nitrogen required by plants is mainly derived from nitrates of inorganic compounds.
In plants, there is a special key enzyme in plant nitrogen metabolism, nitrate reductase (NR), which plays a key role in nitrate nitrite.
Converts inorganic nitrate into a state that can be directly used by plants. The activity of this enzyme directly affects the level of nitrogen in plants, which in turn affects the quality of plants.
Effects of salt stress on plants
Plants have changes in ion uptake under salt stress. The salt is mainly sodium ions and chloride ions, which are harmful to plants.
Due to the high osmotic pressure of the external environment, plants cannot absorb water, resulting in plant nutrient deficiencies. Some people attribute the osmotic pressure of saline soil to "physiological drought" when the osmotic pressure of plant growth is much higher than that of plant growth.
Jingery believed that halophytes reduce metabolism and reduce the amount of salt entering cells by combining with salt.
Therefore, in order to survive in a salinity stress environment, through evolutionary selection, different plants have evolved different mechanisms to deal with the harm of salt to plants.
The photosynthesis of non-halophytes is susceptible to salt, and the degree of reduction is positively correlated with salt content. It is a non-halophytic plant with weak salt resistance, and the photosynthetic rate of Phoenix bamboo will be significantly reduced in the case of low salt concentrations.
With the extension of salt stress time, the permeability of plasma membrane is also increasing, showing a positive correlation trend, which is due to the increasing degree of cell destruction of Bamboo phoenix leaves, so the permeability is increasing.
It shows that in a certain salt stress intensity, with the extension of time, the degree of damage to the cell membrane of Anchovia is increasing.
Chloroplasts are the most sensitive organelles to salt stress, which can cause morphological changes in chloroplasts. For salt-tolerant plants, it does not affect their photosynthesis.
However, it can be seen from the experiment that the greater the intensity of salt stress, the greater the effect on the chlorophyll content of phoenix bamboo. At the same stress time, the greater the intensity of salt stress, the smaller the chlorophyll content.
Moreover, salting can destroy the synthesis of plant proteins, so that the excess ammonia accumulated in the body of the anchovy bamboo has a toxic effect on plants.
In addition, salt stress can also inhibit the protein synthesis of Anchovy and promote the decomposition of protein, and the direct cause of inhibition may be inhibition of amino acid synthesis.
It can be seen from the experiment that under salt stress, the water retention capacity of the leaves becomes worse and worse with the increase of the degree of stress and the extension of time.
Compared with green bark bamboo, phoenix bamboo has poor water retention and is less drought-tolerant. It was indicated that with the extension of salt stress time, the water retention capacity of leaves decreased, and the drought tolerance decreased.
The length of time of salt stress was also negatively correlated with the relative water content of plant tissues, that is, with the extension of salt stress time.
The relative water content of plant tissues is decreasing, and the water saturation deficit is increasing. Over time, irreversible damage to plants is gradually caused.
During salt stress, it is not only sodium ions and chloride ions that cause damage to plants, but also nitrogen, phosphorus, potassium and other elements.
Under salt stress, the content of nitrogen and phosphorus decreased with the extension of time, and the higher the salt concentration, the more obvious the effect on the decrease of nitrogen and phosphorus content.
In contrast, the potassium content in Phoenix bamboo showed an increasing trend with the extension of time, and the higher the salt concentration, the more obvious the effect on the increase of potassium content.
The salt stress forces the imbalance of the concentration of various ions in the bamboo, causing adverse effects. When the salt concentration of Phoenix bamboo was lower than 0.5%, the relative extravasation rate of electrolyte and other indicators changed little.
The relative suitable environment for the growth of phoenix bamboo was 0.5% salt concentration. When the salt concentration was higher than 0.5%, the indicators of Anchovy bamboo changed greatly, which exceeded the tolerance range of plants.
With the increase of stress, the cells of Anchovy also showed irreversible damage, indicating that Anchovy was not suitable for growing in an environment with a salt concentration greater than 0.5%.
Consequences of salt stress
Seed germination is the most sensitive period of the whole seed to salt stress, in the saline environment, the effect of high salt on seed germination includes three aspects, one is osmotic stress, the other is ion toxicity, the third is the inhibition of amylase activity by salt, high temperature will strengthen the damage of salt stress to seeds.
Many studies have shown that salt stress inhibits seed germination.
During plant growth, the effect of salt stress on plants is most obvious. Salinity stress causes plant growth retardation and inhibits the growth of plant tissues and organs.
When seedlings are subjected to salt stress, the root system absorbs salt from the soil and transmits it to the leaves, which is manifested as yellowing and wilting of the leaves, and the new leaves show symptoms earlier than the old leaves.
Observing its underground root system, it can be seen that when the degree of salt stress is light, the plant rarely sees thin rhizomes, and when the salt stress is aggravated, the root system reflects blackening, rotten, unable to absorb nutrients and resulting in the death of plants.
Plant morphology can be used as an important indicator for salt stress judgment. The primary effect of salt stress on plants is that the growth of plant seedlings is disrupted, causing them to stop growing or even die.
For mature plants, salt stress can lead to malnutrition of plants, yellowing and shrinking of old leaves, shedding, and difficulty in extracting new leaves, which eventually changes the appearance of plants.
Salt stress mitigation measures
Under the treatment of 0.15% sodium chloride, the root vitality of A. phoenix decreased and the TTC reduction capacity began to recover to the initial level on the ninth day under the environment of de-salting.
It shows that the anchovy bamboo has a certain tolerance to low salinity, so the damage of the anchovy bamboo when it is stressed by salt is not irreversible, and even if it is treated when the plant is subjected to salt stress, its damage can be repaired.
At the beginning of salt stress, the decrease in the growth rate of anchovy is caused by cell water shortage, which belongs to water stress. This stress recovers a few hours after the salt stress is lifted.
Growth changes that occur after a few days of salt stress with a decrease in new leaves and the death of old and young leaves.
Proline has a water retention effect on plants to a certain extent and can maintain the stability of cell membranes. When anchovy bamboo is subjected to salt stress, it can change the content of proline to enable anchovy bamboo to alleviate the harm caused by salt stress and promote the healthy growth of anchovy.
IV. References
[1] Ecosystem characteristics and resistance of five bamboo species in coastal sandy land——Source. CNKI.
[2] Study on the effect of salt stress on physiological characteristics of bamboo phoenix——Source. CNKI.