Question

Назовите и объясните три фактора , которые могут быть ограничивающими. Скорость фотосинтетических реакций. В световой и темповой стадиях ?

Answer 1

В световой - освещенность. Если много света, разрушается хлорофилл и скорость падает.
В темновой - температура. Если высокая температура, идет разрушение ферментов и снижается скорость фотосинтеза. И концентрация СО2. При фиксации углерода происходит синтез глюкозы. Если мало углекислого газа, то фотосинтез замедлится

Answer 2

Factors that can limit the speed of photosynthetic reactions in the light and dark stages

Photosynthesis is a complex process that occurs in plants, algae, and some bacteria. It involves the conversion of light energy into chemical energy, which is stored in the form of glucose and other organic compounds. The speed of photosynthetic reactions can be influenced by various factors. Here are three factors that can limit the speed of photosynthetic reactions in both the light and dark stages:

1. Light Intensity: Light intensity plays a crucial role in photosynthesis as it provides the energy needed for the process. However, if the light intensity is too low, the rate of photosynthesis will be limited. This is because the light-dependent reactions, which occur in the thylakoid membranes of chloroplasts, require sufficient light energy to drive the electron transport chain and generate ATP and NADPH. If the light intensity is too low, the production of ATP and NADPH will be reduced, leading to a slower rate of photosynthesis. Additionally, low light intensity can also limit the opening of stomata, reducing the availability of carbon dioxide for the Calvin cycle, which occurs in the stroma of chloroplasts.

2. Carbon Dioxide Concentration: Carbon dioxide (CO2) is another essential factor for photosynthesis. During the light-independent reactions (Calvin cycle), CO2 is fixed and converted into glucose. If the concentration of CO2 in the surrounding environment is low, the rate of photosynthesis will be limited. This is because the enzyme responsible for carbon fixation, RuBisCO, has a higher affinity for oxygen (O2) than for CO2. In conditions of low CO2 concentration, RuBisCO can bind with O2 instead of CO2, leading to a process called photorespiration. Photorespiration consumes energy and reduces the efficiency of photosynthesis.

3. Temperature: Temperature affects the rate of photosynthesis by influencing the activity of enzymes involved in the process. Both the light-dependent and light-independent reactions are temperature-sensitive. At low temperatures, the enzymes involved in photosynthesis may have reduced activity, leading to a slower rate of photosynthesis. On the other hand, at high temperatures, the enzymes can become denatured, losing their structure and function. This can also lead to a decrease in photosynthetic activity. The optimal temperature for photosynthesis varies among different plant species, but it generally falls within a range of 20-30 degrees Celsius.

In summary, the speed of photosynthetic reactions in both the light and dark stages can be limited by factors such as light intensity, carbon dioxide concentration, and temperature. These factors directly or indirectly affect the availability of energy and substrates required for photosynthesis. It is important for plants to maintain optimal conditions for photosynthesis to ensure efficient energy production and growth.