RECOGNITIVE TASKS ON THE TOPIC: "PHOTOSYNTHESIS"
1. It is known that 50 m2 of green forest absorbs in 1 hour of carbon dioxide as much as it releases during breathing in 1 hour one person, ie 40 g. How much carbon dioxide does one hectare of green forest absorb in one hour? How many people can breathe out this carbon dioxide in the same hour?
2. The root weight of a small tree is 5 kg. One kg of root mass consumes 1 g of oxygen per day. How much oxygen do tree roots consume per month and year?
3. Which plant deposits more dust on the leaf surface: elm or poplar? Why?
4. Is there a relationship between picking leafy vegetables (dill, spinach, lettuce, etc.) and the time of day? Why?
5. The hostess at the summer cottage cut off the green leaves of cabbage to feed the rabbits. Did she do the right thing? Why?
6. A person consumes 430 g of oxygen per day. One hectare of forest produces as much oxygen per hour as is needed for the breathing of two hundred people. How much oxygen does a hectare of forest emit in one hour?
7. In the process of photosynthesis, cucumbers grown in greenhouses absorb 1 kg of carbon dioxide while producing 7 kg of fruits. How many kg of carbon dioxide gala will it take to get 300 kg of cucumbers? How can you increase the carbon dioxide content in greenhouse air?
8.K.A. Timiryazev wrote: "In essence, whatever the farmer produces, he first of all produces chlorophyll and already through chlorophyll obtains grain, fiber, wood, etc." what agrotechnical methods contribute to the accumulation of chlorophyll and enhance the processes of photosynthesis in the pulp of the leaf?
Discussion in Biology started by Komarova, Apr 2, 2018.
- Komarova Meluzga Member since Apr 18, 2013 Posts: 0 Likes: 0In the process of photosynthesis, cucumbers grown in greenhouses absorb 1 kg of carbon dioxide in the formation of 7 kg of fruit. How many kg of carbon dioxide will it take to get 300 kg of cucumbers? How can you increase the carbon dioxide content in greenhouse air?
Komarova, Apr 2, 2018 # 1
- Lolitacity Small Fry Joined: Feb 26, 2013 Posts: 0 Likes: 0You can increase the space
Lolitacity, Apr 2, 2018 # 2
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The beginning of the agricultural season is an excellent occasion to talk about the pressing problems of the new greenhouse season, about our life and our plant life.
The modern realities of agricultural production with the onset of the global crisis force us to reconsider the relationship of a small former to greenhouse production. Today, greenhouse farming is becoming too expensive a pleasure to be able to work without good theoretical training. The level of technological thinking is clearly demonstrated by numerous field days, in terms of questions and answers. Sometimes they ask such questions that one gets the impression that we receive everything that grows in the fields rather in spite of than due to efforts.
All (or almost all) are looking for some universal formulas, super-secrets, methods for all occasions - a kind of philosophical stone of agronomy. Alchemists won, too, a couple of centuries looking for this universal means of enrichment, so what? And the idea is the same: with a minimum of brain effort, get a swing full of your pocket, often spending enormous physical efforts, and the return can tend to 0 - as a result, your arms, legs, wife and children suffer.When problems arise, you have to solve 2 textbook questions "What to do and who is to blame?" If the second always has a full range of answers - from bad seeds and weather to the government and the hryvnia exchange rate, then the first one often remains unanswered. Practice shows that "Western" cucumbers, like their growers, live better than their Ukrainian fellow tribesmen. And foreigners know the main secret of success - in order to make the plant work to the maximum, you need to know thoroughly the needs, nature and tastes of their plant life and build all agricultural technology according to this. From major to minor.
They look at the charts and tablets of smart alphabet books - frantically trying to find answers to the daily changing questions.
They look at the plant, the sun and a dozen devices - they RUN the life in the greenhouse.The most adventurous try to master plant physiology in one sitting. Bottom line: after a meeting with adenosine triphosphates, cyclic photophosphorylation and Calvin-Benson cycles, it is clearly read on the face, and immediately proceed to the more understandable and practically implemented sections "feeding, watering, protection, etc."
Therefore, whoever is not going to capitulate to the pros from modern greenhouse complexes with oligarch owners - you are welcome to visit the difficult world of plant life, on the pages there are several fragments from the book "Physiology - available about the complex". Let's try to understand the intricacies of plant, and specifically, cucumber life.
The main thing that distinguishes plants from all other organisms is photosynthesis. Therefore, let's start with him.
WHAT IS PHOTOSYNTHESISIn order not to bore readers with complex terms and an explanation of what and how it works, we will set out the necessary minimum, according to the principle that if Schumacher thoroughly studies the theory of automobile engines, he will not be better off driving.
So let's look at a greenhouse plant as a machine. If the heart of a car is a motor, then green leaves and the photosynthesis taking place in them are the power plant, the green engine of plants. Photosynthesis is the most important process in plant life. It provides 95% of the plant mass and 100% of the energy used in plant development. Therefore, the harvest depends on the ability to manage this process.
The process of photosynthesis is complex, multistage and consists of a large number of sequential reactions, because it was not in vain that the work on its research was awarded the Nobel Prize in 1961.
Speaking without formulas and poorly spoken terms, the essence of the process is as follows:
In green leaves, water and carbon dioxide are chemically converted into sugar-carbohydrates using light energy - it's like making money.
carbohydrates, as energy currency, are supplied from the leaf to all points of the plant, and as a result of respiration (the process opposite to photosynthesis) they break down, and the released energy is used for all the plant's needs, this is already a waste of money. Breathing is a round-the-clock process and is mainly regulated by temperature.
And by and large, the basis of plant life is absolutely similar to ours - the money earned should be more than spent.
Conditions for photosynthesisThe sun, air and water are our best friends, they remember everything from the kindergarten. However, this is also true for plants, in particular, the gentle sun, moist air and warm water are useful for cucumbers.
The first and main condition for photosynthesis is the presence of an energy source, which is solar or light energy. The plant absorbs 85-90% of the light energy falling on it, but only 1-5% of them goes to photosynthesis. The rest goes to heating the sheet and evaporating water (transpiration). For optimal photosynthesis, it is necessary that the leaf receives enough light energy. The second prerequisite is water supply.The amount of water used for photosynthesis, as in the case of energy, is a small part of the total amount absorbed and evaporated by the plant. Lack of water reduces the rate of photosynthesis - the stomata (leaf pores) close, and the supply of carbon dioxide, which is the third necessary factor in photosynthesis, stops. The dry matter of plants contains 45% carbon, 1.5% nitrogen and 5% and other mineral elements. Therefore, carbon dioxide is doubly valuable - in addition to plant fuel, it is also the main building material of a plant. On quizzes, the question is often asked: "What is the most important nutrient in a plant?" Everyone shouts: "Nitrogen!" But no - CO2.
Temperature is already a secondary factor and acts as a regulator of the rate of the photosynthesis process itself. The optimal temperature for photosynthesis of cucumber is in the range of 25-30 ° C, although these temperatures are not optimal for the growth of the whole plant (with increasing temperature, respiration increases more than photosynthesis).
Just as important as the governing factor and the photoperiod is the alternation of day and night. During the light period, there is mainly the conversion of light energy into chemical energy compounds. And in the dark, sugars are formed from water and carbon dioxide and transported through the plant.
Let us consider all this in more detail in order to draw conclusions that connect theory with practice. Straight through the list and let's go:
Influence of illuminationK.A. Timiryazev wrote: "The limit of fertility of a given area is determined not by the amount of fertilizer that we could deliver it, not by the amount of moisture that we irrigate it, but by the light energy that the Sun sends to a given surface."
Light energy (the Sun) through the intensity (quantity) and spectral composition (quality), as it were, guides the entire life of the plant, indicating how and what to do, i.e. in addition to providing energy for photosynthesis, it gives signals to control the development of plants (photomorphogenesis). Information about the spectral composition of sunlight is difficult for us to use in practice, we cannot influence them, we will skip this information and return to considering the composition of light in the section on growing seedlings and using artificial lighting.
For greenhouses, the main thing in lighting is the amount, which determines the need for plants in other conditions - temperature, humidity, nutrition, air.
With a sufficient amount of light, photosynthesis in a plant is many times more intense than respiration, therefore, synthesized substances accumulate in them. As the illumination decreases, the process of photosynthesis weakens, and the moment of equality of the production of products and their consumption may come. With a further decrease in illumination, the process of consumption by respiration prevails over the production of photosynthesis, and the previously accumulated substances begin to be consumed. As a result, growth stops, the ovary falls off, the leaves turn yellow and fall, and the plant dies (a vivid example is growing seedlings in an apartment on a windowsill under a battery without additional lighting).
Intensity
In cucumber, photosynthesis exceeds respiration, starting with illumination of about 2000 lux. Normal vegetative growth at 6000 lux, development and fruiting at an intensity of 10,000 lux. It is generally accepted that an increase in illumination by 1% inside the greenhouse also increases the yield by 1% - the productivity of a cucumber to a large extent depends on the intensity of illumination, because they do not naturally have a high capacity for photosynthesis. This pattern remains in the range of 20,000–40,000 lux. With a further increase in illumination, the increase in photosynthesis decreases until it reaches the saturation point. Very high illumination of 60,000-80000 lx inhibits plants, causing severe overheating of plants and burns.
The effect of light on a plant is manifested both directly (energy for photosynthesis) and indirectly - heating of plant tissues, air and soil.In the summer months, good turns into harm in accordance with the proverb - "If it is zanadto, then it is not healthy." We have to fight - to shade the plantings with whitewash chalk or a light curtain, they begin to ventilate. But more about this in the section "Ventilation".
In older plants, self-shadowing of the leaves occurs, and in low light, the setting of flowers and the growth of fruits are disrupted due to a decrease in the availability of photosynthetic products - a decrease in the level of light leads to the formation of thinner and larger leaves. The intensity of photosynthesis of cucumber leaves decreases with its age - as soon as external signs of aging appear.
Temperature and photosynthesisThe amount of light also determines the temperature regime in greenhouses, which is controlled to increase the productivity of photosynthesis. With high light intensity, the daytime temperature is increased, with a decrease, it is reduced.
When sunny weather changes to cloudy, less products of photosynthesis are produced, and there is a delay in the growth of fruits and shoots due to the increased consumption of roots in the heated soil for respiration.
For example, in winter with low light levels, yields were greatest at 21 ° C and did not increase with increasing temperatures.
Fruiting clearly shows what stock of photosynthetic products the plant has accumulated during daylight hours. At night, the products of photosynthesis move to points of growth - fruits, shoots and roots. The night temperature sets the speed of this movement, as well as the intensity of breathing, which gives energy to this process. So, if few products of photosynthesis have been accumulated during the day, then they will be distributed in a short time and until the morning they will be uselessly spent on breathing (this is like idling the engine at high speeds). As a result, both fruit growth and root development will decrease, or even stop altogether. Conclusion - the night temperature should take into account the level of illumination, and with it the accumulation of photosynthetic products over the previous day. It should be borne in mind that after a period of stable sunny weather, the accumulated products of photosynthesis are consumed within 2-3 days.
In cucumber plants, there is very strong competition for photosynthetic products between fruits and roots. As the fruit grows, the growth of the leaves decreases and the roots begin to die off. After the fruit is removed, the root system grows rapidly. These are the cyclical waves of development (and the yield of the crop) they try to regulate by night temperatures. At low temperatures of 15-17 ° C, the products of photosynthesis are slowly transported and more evenly distributed between the ovaries. At a high temperature of 18-20 ° С, the growth rate increases, but competition also increases, and some of the ovaries die off, deformed ones may appear, especially if the difference between day and night temperatures exceeds 6 ° С.
Conclusion - when fruiting in waves, it is necessary to reduce the night temperature to 15-16 ° C, which allows you to restore the root system.
Such processes are characteristic of early spring, and when the arrival of light energy increases significantly, and with it photosynthesis, the processes of competition become less obvious. Particular attention is needed at the beginning of fruiting - many people think: to remove the first ovary or not? Based on the above, you need to choose - or get one cucumber, but very early, and which is likely to slow down the development of the plant for a week, or even more, or remove the first ovaries and direct all photosynthesis to the development of leaves and roots, which will eventually give higher early yield of uniform fruiting.
Young plants require a higher temperature regime for leaf growth, and at the beginning of fruiting, the temperature is reduced. The level of night temperatures also determines the nature of the formation of the leaf apparatus. At a temperature of 16 ° C and below, many lateral shoots are formed and a bundle ovary is laid at the nodes on the main stem.
Different varieties have their own optimal temperature regimes, they are described in all textbooks, it is more important for us to see the processes that they represent behind the numbers.
Photoperiod
The response of plants to day length is related to their geographical origin. Cucumbers come from the tropics, therefore, according to the duration of illumination, the cucumber is a neutral short-day plant - it accelerates development with a day length of 12-14 hours (March-April, August-September). In principle, modern varieties bear fruit well under long day conditions. If in the summer months the duration of the light period is artificially reduced to 10-12 hours per day, with an excess of solar radiation, then they will react by accelerating the formation of the ovary. A short day is especially favorable when growing seedlings, but naturally at high light intensity.
Adjustment methods
light mode
The easiest way is to keep the greenhouse clean, cover the soil with reflective material (light sawdust, straw, white film), remove dust, dirt and algae in a timely manner to increase light transmission, the paths should also be light. In greenhouses, pipes and frames are painted white.
All agrotechnical care work should be aimed at ensuring that the plants make the most of the light, reduce as much as possible the obstacles to the penetration of the upper light to the plants, placing the plants at an optimal distance from each other from 2.0 to 3.5 plants / m2. In sparse plantings, part of the light is wasted, and in thickened plants they shade each other, the planting scheme is determined in each case. In some cases, the planting density is reduced in order to increase their individual illumination. Although this reduces the number of plants per unit area, the productivity of each of them increases. Plants can be planted more densely near paths, as they are better lit here.
If the conditions for water supply and nutrition are improved, then the size of the leaf blade will increase, and there is usually a direct relationship between the area of the leaves and the size of the yield. With a certain size of leaves, plants absorb almost all the light, then as a result of shading, the intensity of photosynthesis decreases - the yield in the lower tiers decreases. Then a clarifying sanitary cleaning of the leaves is necessary.
Condensation on the film also reduces light output by 25% and can significantly reduce early harvest.
Conclusion - the choice of optimal conditions for root nutrition, temperature regimes, feeding with carbon dioxide does not make sense when a cucumber greenhouse looks like a dense forest. Growth and development, and ultimately the harvest, will be limited by photosynthesis.
Vitaly Lobas, farmer - agronomist, Ukraine, Cherkassy
Real Master, Kiev
