Exchange of scientific knowledge

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Today's topic is biology! ! !

How do children feel under a big tree in summer?

It's good to enjoy shade under a big tree:

(1) Direct light principle. Light is blocked by leaves and cannot directly shine on ground, so people's skin cannot be exposed to sunlight. Through photosynthesis, leaves convert part of sun's energy into chemical energy and store it in plants. Under a large tree, it will completely absorb solar energy and heat up less than bare ground, and temperature is also slightly lower.

(2) The water in leaves undergoes transpiration (that is, evaporation of water), absorbing heat from environment, which reduces temperature under tree.

(3) The temperature of ground under trees is lower than that of ground in direct sunlight, and it is damp. Moisture means there is more water, making specific heat capacity higher than normally dry soil. and temperature rises for a long time.

(4) Uneven heat under a large tree creates an airflow and accelerates airflow under a large tree. Hence coolness under big tree.

What happens when you peel an apple?

The apple turns yellow:

After peeling apple, phenolic substances in cells react with atmospheric oxygen under action of phenolase to form a large amount of quinones.

Natural quinones can quickly stain cells brown, a change called enzymatic food browning.

An apple will turn yellow after being peeled.

This situation happens not only with apples and pears, but also with some vegetables.

If apples are left for a long time after peeling, oxidative decomposition of cells in air will increase,

Then, nutrients in outer layer of apple decompose more, and pectic substances are further broken down into pectic acid and methanol by action of enzymes.

From it, pulp becomes loose, moist, changes color, taste and even rots.

Look at picture and observe

Where did leaves go?

Falling leaves return to their roots:

After leaves fall, most of nutrients in leaves will be lost, especially some of Mg, which will eventually cause leaves to lose their green color and turn yellow. And water in leaves will gradually disappear, making leaves dry. It will eventually be broken down by bacteria and then turn into soil.

Collect fallen leaves and stack them near tree roots. After natural degradation, it can increase soil organic matter content, improve soil aeration, improve soil water and fertilizer holding capacity. , adjust acidity and alkalinity of soil, and make trees grow next year.Grow more lush. In addition, placing bedding on surface of soil can also suppress dust, keep soil warm and moist, and prevent weed seeds from germinating normally in soil. After fermentation, fallen leaves are better absorbed by plants than original fallen leaves. The bedding is shredded with a twig and leaf shredder, and leftovers are sterilized with fungicides and insecticides, then stacked and soaked, fermented and decomposed to produce manure that can promote growth of flowers and plants.

Did the children look at what happened to this sheet?

Did children look at what happened to this sheet?

Withered leaves:

Active defoliation in dry, cold air conditions in winter can reduce water loss and nutrient intake, so a hormone called abscisic acid will be released during this time, which causes leaves to drop. When abscisic acid reaches base of petiole, it forms a layer of parenchyma cells called abscissa layer to prevent water transport to leaves. dry up. When leaves dry, they will break at point of fall, and then fall off by themselves under influence of an external force or their own weight.

After a certain period of physiological activity, leaves accumulate a large amount of metabolites in cells, such as minerals, which causes a decrease in physiological functions and death (destruction of chlorophyll).

The weather is getting colder, soil temperatures are dropping, rainfall is decreasing, and water-absorbing capacity of root system is greatly weakened.

People should drink water, but what about plants?

Plants drink water:

Watering plants should contribute to their normal growth, because plant growth is inseparable from water, with a lack of water, plants will dry out and die, only timely watering can replenish water necessary for plant growth.

(1) Water is main component of protoplasm

The water content of protoplasm is usually between 70% and 90%, so that protoplast is in an ash state, which ensures an active metabolism, for example, in tips of roots and tips of shoots. If water content decreases, protoplasm will pass from state of sol to state of gel, and vital activity will be greatly weakened, for example, in dormant state of seeds.

(2) Moisture is a reactive substance in metabolic process

The processes of photosynthesis, respiration, synthesis and decomposition of organic substances involve water molecules.

(3) Water is a solvent by which plants can absorb and transport substances.

Generally speaking, plants cannot directly absorb solid inorganic and organic substances, and these substances can only be absorbed by plants when they are dissolved in water. Similarly, transport of various substances in plants must be dissolved in water.

(4) Water can maintain inherent posture of a plant. Since cells contain a lot of water, cell tension (i.e. swelling) is maintained so that branches and leaves of plants stand upright, which is convenient for full light reception and gas exchange.