Plant Physiology Test 13

By Joann Patterson,2014-05-06 12:34
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Plant Physiology Test 13

    Plant Physiology

题序 1 2 3 4 56



    Part 1: Explain terms (Select 8 terms from followings5 marks for each and total

    40 marks.)

1. Root pressure

    Root pressure is a power which pushes water to mount along vessel, depending on

    physiological activity of root.

    2. Critical period of nutrition

    A period during which plant is most sensitive to nutrition deficiency and is most easily

    injured by this, but the nutrition requirement is not always largest at that period.

    3. Cpathway 3

    It is referred as a photosynthetic pathway in which the initial product of photosynthesis in

    CO fixation is Ccompound. 23

    4. Cyclic electron transport

    A kind of photosynthetic electron transport around PSI in which the excited electron

    starts to transport from PSI to several electron carriers such as Fd, PQ, Cytbf and PC and

    return to PSI. The transport only generate a supplementary of ATP.

    5. Cytochrome oxidase

    Cytochrome oxidase is one of a superfamily of proteins which act as the terminal enzymes of

    respiratory chains. The enzymes are vectorially arranged so as to transfer charge across the

    membrane as electrons are passed to O. The electrogenic process is contributed by vectorial 2+electron transfer, and the uptake of H on reduction of O. 26. Transfer cell

    Transfer cells are specialized companion cells that have an increased surface area, due to

    infolding of the plasma membrane. They extensively exist in source or sink organs and

    facilitate the transport of assimilate from apoplast (cell space) into phloem or inversely.

    7. Growth inhibitors

     The synthetic 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.

    8. Photoreceptors

    One kind of micropigments in plant which can receive the signal of light such as the

    direction and intensity of light, magnifying the signal, as a result, and the plant will make

    corresponding reaction. They are photochrome, cryptochrome or blue/UV-A receptor and

    UV-B receptor.


9. Short-day plant

    The plant can only flower under daylength shorter than its critical day length of 24 h cycle.

    Such as morning glory, cocklebur, chrysanthemums, tobacco, late soybean, late rice and late


    10. Physiological drought

    One kind of drought happens in plant body. It is referred to all phenomena that make plant

    body water imbalance because water absorption is less than water loss in plant body. Air or

    soil drought, salty and chilling or heat injury etc often cause physiological drought of plant.

    Part 2: QestionsTotal 60 marks. 1234 are necessary to answer and chose one

    of 5 and 6.

    1Why does low temperature make plant decease in water absorption 7 Marks

    At low temperature, water can not easily diffuse into cell as water and plasma viscosity increase

    and water conductance decreasesThe active absorption depending on ATP decreases because respiration lowers; Less area for water absorption is due to slower root growth and poor root hair


    2Describe steps of nutrient movement from bulk soil to root surface and across membrane.

    (7 Marks)

    The nutrient movement from bulk soil to root surface involves interception and ion exchange,

    diffusion, mass flow and the nutrient uptake cross membrane carries out through passive transport

    (simple diffusion, facilitated diffusion (carrier and ion channel) and active transport by ion’s carrier or/and pumps.

    3Introduction to relationship between plant hormones and plant flower formation10


    Most of plant hormones can influence plant flower formation. GA and Eth are well known

    plant hormones which regulate flowering. GA can promoting bolting and flowering instead of

    low temperature and long daytime and enhance male flower initiation of cucumber but female

    flower initiation in a lot of tree. Eth can promote male flower initiation of many kinds of plants,

    especially for cucumber, pumpkin etc. IAA also enhances male flower initiation and flowering due

    to induction of Eth.

    4How to keep the fresh fruits, vegetables and store the dry seeds longer in basis on

    principle of respiration?15 Marks

    High respiratory rates of fresh fruits, vegetables and the dry seeds will consume more stored

    organic nutrition of them. Therefore it is most important for them to reduce the respiratory rate

    during the storage periods. The respiratory rate can be greatly impaired by microorganism,

    environmental conditions and inner ethylene concentration. If you want to store them longer,

    following things should be done.

    When keep the fresh fruits, vegetables longer, you choose no wounded ones at first; then you

    keep it at lower temperature, but a bit of higher than cold injury temperature; third, you control the

    gas components, higher CO

     and lower O, still but higher than exhausting point; Fourth, you 22remove Eth by suitable ventilation or you use gene modification (transgenic plant)-------anti ACC

    synthase to protect fruit repine like tomato


    When keep the seed and food longer, you fully dry the seeds and control the seed water

    content below safety water content, in which seed can be stored one cycle year or do

    seed-ultradried storage ; you can lower food temperature to -4 ~4 ?, even super-low temperature storage-193?); And you regulate gas components by filling with N, COor autonomously 22 decrease in O by respiration as well as you use the chemicals to kill the microbe or insects. 2

    5What does greenhouse effect impact to plant growth and development21 Marks The greenhouse effect is due to increased emissions of COand CH, which made the short-wave 2 4of solar radiation conducted through the atmosphere while the infrared radiation come back to the

    Earth's surface by reflection, so atmospheric temperature increased. CO and temperature is the 2greatest impact on the flower and plant photosynthesis.

    According photosynthetic pathway different plants can be divided into C, C and CAM. 34Generally believed that increased CO concentration will increase the net photosynthetic rate on 2

    C plants, but in high temperature areashigh temperature will increase light respiration and dark 3

    respiration, resulting in net photosynthetic rate reduction. However, in most areas, increased

    accumulation will accelerate growth.C plants need vernalization to blossoming; a rise in 3

    temperature in this part will affect plant propagation.

    Recently, many studies show that long-term increased CO concentration in plant will lead to 2

    photosynthesis down, so the problem is more complex. On C plants, the concentration of 4atmospheric CO has reached the saturation point, a rise in CO concentrations cannot lead to 22increased photosynthesis and accelerated growth, but the high temperature will increase

    respiration, it gives rise to negative growth. This tends to a disadvantageous position while

    compete with C plants, having the potential to reduce the population. On the CAM plants, an 3

    increase in CO concentration will increase its absorption of CO at night, improving the 22photosynthesis during the day.

    Because of the greenhouse effect may also cause drought, so the impact of different plants

    photosynthesis means no conclusion has been drawn. Under present knowledge, there is not

    enough time to study some of the conclusions and conjecture, it need further study.

    6What should we provide the plant for growth better in facility culture21 Marks

    The plant is affected by lots of environmental conditions such as light intensity,

    temperature, soil moisture, nutrition concentration and abiotic stresses etc.

    In facility culture we should provide the plants sufficient light intensity and light quality

    by covering with transparent material which can even pass through a part of UV in order to

    photosynthesize and prevent the plant overgrowth. We should control the temperature to

    about growth suboptimum and the larger difference in temperature between day and night

    (about 10 ? higher in daytime than at night ) and ventilate in order to provide enough CO 2in the facility. We should keep the soil or substrate moisture neither too wet nor too dry and

    provide enough all essential elements to plant. If the plants are cultured with hydroponics, it

    is necessary to use flow culture or airing. If the plants are cultured in the soil directly, it is

    necessary to prevent soil from salty. We should shower the soil for other several seasons to

    avoid salt stress.

     In facility culture pests and diseases often break out and make harmful to plants, we

    should carefully deal with them by using pesticides which can kill the pests or pathogens but


safe to human beings. Sometime we should breed special insects to help plant pollination

and use plant hormone for promotion of setting.


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