浙大植物生理学三套题及答案3answer.doc

《Plant Physiology》模拟试卷三参考答案

题序
一
二
三
四1
四2
四3
四4
四5（6）
总 分
得分

评卷人

Part 1: Explain terms (Select 8 terms from followings，5 marks for each and total 40 marks.)
1.Symplast: Symplast of a plant is the inner transport system of the plasma membrane in which water (and low molecular solutes) can freely diffuse. A continuous system is consist of protoplast, plasmodesma and plasmic menbrane, except apoplast.
2.transpiration pull: A pulling force that pulls water up the xylem vessels of stems due to transpiration.
3.Donnan equilibrium: The Donnan equilibrium is a phenomenon of solutions that contributes to the formation of an electrical potential across a cell membrane. the product of the diffusible anions and cations inside of the cell is equal to outside of the cell.
4.Primary reaction: It is the beginning of the photosynthesis, containing the absorption of energy, the transfer of energy and photochemical reaction. This reaction is very fast, the time of reaction is 10-9~10-12s.
5.Pentose phosphate pathway (PPP): Pentose phosphate pathway is primarily an anabolic pathway that utilizes the 6 carbons of glucose to generate 5 carbon sugars and reducing equivalents. This pathway does oxidize glucose and under certain conditions can completely oxidize glucose to CO2 and water.
6.Energy charge regulation Adenyl acid levels reflecting the energy levels in cell regulate the respiratory metabolism.
7.Sugar-proton symport: A model for sucrose transport into phloem across sieve/companion complex plasma membrane, in which sucrose and proton are chemometrically symported into sieve/companion complex from apoplast, usually the mesophyll cell space by the transporter.
8 Growth retardants: Compounds resistant to GAs in function and inhibit the growth of the subapical meristem. The inhibitory effect can be reversed by GA, but not by IAA.
9. Redifferentiation: A process by which callus in tissue culture or section in cutting can differentiated new organs to complete a plant.
10.Long-day plants: The plant can only flower under daylength longer than its critical day length of 24 h cycle.Such as wheat, rye, henbane, beet,carrot etc.They usually flower in spring end or summer.

Part 2: Qestions（Total 60 marks. 1，2，3，4 are necessary to answer and chose one of 5 and 6.）
1.Why can plants be watered with cold water in the summer noon？（5 Marks）
In the summer noon, because of high temperature and low relative humidity, the transpiration is very high. If plants are watered with cold water, which will decrease the soil temperature and than decrease the water absorption by root, the plants will wilt even death by disorder of body water balance as loss of water by the transpiration is less than uptake of water by root.
2. What is Eth used to in plant production? （5 Marks）
Ethylene is commonly used as a fruit ripening regulator for shipment and inducing abscission as a defoliant for cotton etc mechanical harvest because it increases in the activities of pectinase, peroxidase and cellulase in abscission zone. It is also used to thinning fruit or flower in tea, grape and Carya illinoensis. It can enhance female flower formation and the secretion of secondary products for oak etc.
3. Where do C4 and C3 pathways undergo in C4 plant, respectively? What is relationship between the both pathways? （10 Marks）
C4 and C3 pathways undergo in mesophyll cell and chloroplast stroma, respectively. The whole photosynthesis initiates in the cytosol of mesophyll cell where PEPase catalazes PEP and HCO3- to form OAA. Then it is transported into chloroplast of mesophyll cell and reduced to Mal or transaminated to form ASP. They are transported into bundle sheath cell, decarboxylated, and the CO2 enters C3 pathway in the chloroplast of bundle sheath cell. Therefore ,C4 pathway as a CO2 pump to provide higher concentration CO2 to C3 pathways. That is to say, the relationship of C4 and C3 pathways are complementary.
4. Describe the application of principle of vernalization and photoperiodism to agricultural production. (20 Marks)
Vernalization refers low-temperature promotion of flowering. It is extensively used in the production.We can control vernalization that winter wheat can be sown in spring after vernalization treatment,which can harvest in summer and devernalization that angelica and onion can be treated with higher temperature in winter to enlarge the tubes in next season and so on.. We should control sowing time for the plants (crops) requiring for vernalization to meet low temperature during seedling stage and guide to introduce seed to various regions, if the crop needs vernalization.
The response of plant flower (development) to photoperiod (day length of 24 h cycle) is called as photoperiodism. Photoperiodism is useful to introduced crop. We must obey the principles in the Northern Hemisphere, that SDP induced from south to north, growth stage longer, early matured cultivar can be done. On contrary, from north to south, growth stage shorter, lately matured cultivar can be done. LDP induced from south to north, growth stage shorter, lately matured cultivar can be done. On contrary, from north to south, growth stage longer, early matured cultivar can be done. But it is just opposite to the Southern Hemisphere.
Photoperiodism is used for select suitable sowing stage, for instance, SDP or LDP or DNP. Genetic male sterility induced by daylength.
Photoperiodism is used to regulate flower time. Two parents flower at same time. in hybrids. Flash flower production should meet the expensive flower season by delaying or enhancing flowering controlled by SD or LD. For example, SD treatment make chrysanthemums flower early and darkness broken (extension of day time) results in flower late.

5. How to promote the water utilization efficiency on the basis of different photosynthetic pathways of plants? (20 Marks)
Water utilization efficiency (WUE) is a ratio of net photosynthetic rate to transpiration rate or dry matter to water consummation during the whole stage. Therefore, it is significant in the practice to keep the same net photosynthetic rate and decrease the transpiration rate or to maintain the same transpiration rate and increase the net photosynthetic rate.
Transpiration is defined as a loss of water in a form of vapor, by which water loss passes mainly through the stomata in the epidermis of the leaves. CO2 for photosynthetic raw also enters leaf through the stomata. It is necessary for highest water utilization to control a suitable opening of stomata during the daytime, which keeps lower transpiration rate, but not limit photosynthesis.
Based on photosynthetic pathway, the plants can be divided into three types: C3 plants, which only carry out C3 pathway, C4 plants which have C4 (in mesophyll cells) and C3 (in bundle sheath cells) pathway and CAM (Crassulacean acid metabolism) plants which have C4 (at night) and C3 (during the daytime) pathway. The 3 types have different water utilization efficiency because they are different photosynthetic capacity and optimum CO2 concentrations. For C3 plants, sufficient water has higher photosynthetic rate and WUE, but alternative irrigation and less-water in the seedling stage can obtain the highest WUE due to keep the same photosynthetic rate as full irrigation and lower transpiration by stomata less-opening, For C4 plant, Less water application is favored for the highest WUE because C4 pathway called CO2 pump can concentrate CO2 to satisfy the highest photosynthetic rate even the stomata open less. For CAM plants, it is adapted in the dry condition. Usually we need not irrigate them but very dry conditions.
We also can use same principles to enhance WUE, such as water requirement, growth stages, and irrigation technology.
6. How does greenhouse effect impact plants with different photosynthetic pathways? (20 Marks)
The Greenhouse effect is due to increased emissions of CO2 and CH4 in the earth, causing the short wave of solar radiation into the atmosphere, and the infrared radiation of earth can not reflect to universal space, resulting in atmospheric temperature rising continuously. This phenomenon is like the process of sun heating glass greehouse. Greenhouse has the greatest effect on that CO2 and temperature affect plant photosynthesis and flower, for the plant growth and development of different photosynthetic pathways.
According to the different photosynthetic pathways, plants can be divided into C3, C4 and CAM plants. The different plants have the different responses to increasing CO2 and temperature.
It generally was believed that the increased CO2 concentration increased the net photosynthetic rate of C3 plants. But in high temperature area, high temperature will make light and dark respiration increased, resulting in the reduction of net photosynthetic rate. However, in most area, the substance is accumulated, the growth is accelerated. The part of C3 plants need vernalization to flower, the raised temperature will not satisfy plant flowering requirement for low temperature and the plants will not flower and propagation. Recently, many studies show that increased CO2 concentration of will lead to long-term reduction of plant photosynthesis. For C4 plants, the concentration of atmospheric CO2 has reached saturation point. Increasing CO2 concentrations will not lead to photosynthesis increased, but the growth accelerates. And the high temperature will increase respiration. It gives rise to negative growth. C4 plants will become unfavorable position with the competition of C3 plants. This strain is likely to be reduced.
For CAM plants, an increase in CO2 concentration will increase its absorption of CO2 at night, improving photosynthesis at daytime.
Because of the greenhouse effect may also cause drought, and so the impact of different photosynthetic pathway plant haven’t been concluded. Under present, we have only a little evidence. In order to reach a conclusion, we must need further study.

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