Temperature as ecological factors

Temerature as an ecological factors. Plants classification on the basis of temperature. Adaptation of Plants for Temperature change.

1. Topic Temperature

2. It is a measure of how hot or cold an object is compared to another object. Temperature  as a measure of the average kinetic energy of the particles in an object It is measured by the Thermometer. Definition:

3. Temperature is one of the most important  ecological factors . It regulates many physiological processes of the plant. The metabolic processes are low at a certain minimum temperature. It increases at particular temperature called optimum temperature. The plant grows best at optimum temperature . Metabolism again decreases at maximum temperature. The plants cannot survive above this temperature Both extremely low and high temperatures have adverse effect on plant growth. Temperature is an ecological factor

4. Low temperature :   Low temperature causes cold injuries. Water is frozen into ice crystals in the intercellular spaces. It causes injury to cells.

5. High temperature :   Extremely high temperature cause adverse effects on a number of vital physiological processes like respiration, transpiration, protein metabolism etc . These effects cause stunting and finally death of plants. This is called as Heat Injury . Different kinds of plants have various ranges of minimum-optimum-and maximum temperatures. Plants differ considerably in temperature tolerance. Generally , there is little metabolic activity at temperature below 0°C or higher than 40°C. 

6. Temperature classification of plants The plants are classified into the following categories on the basis of temperature requirements . 1 . Megatherm :   The plants live in high temperature throughout the year are called megatherms. These plants are found in equatorial and tropical rain- forests.

7. Mesotherm :   The plants living at high temperature of summer, alternating with low temperature of winter are called mesotherms. They are found in deciduous forest of tropical and subtropical regions.

8. Microtherm:   The plants which live in extremely low temperature are called microtherms. It includes plants of temperate and high altitudes (upto 12000 feet of tropical and subtropical region). These regions are dominated by mixed Coniferous forest.

9. Hekiskotherm:   It includes plants of Arctic and Alpine regions • (above 16000 feat in tropics and 12000 feet in temperate) with very low temperature. Alpine vegetation prevails in such locality.

10. Ecophyiological responses of temperature Temperature is an ecological factor. It affects the rate of many physiological processes in plants. Transpiration :   Rise in temperature increases transpiration rate. High temperature influences the saturation deficit of the atmosphere. It decreases the humidity of air. Thus more water is transpired. High rate of transpiration also increases the rate for absorption of water from the soil.

11. Photosynthesis :  Photosynthesis occurs over a wide range of temperature. In some desert plants photosynthesis continues even at 80°C. Most of the algae require lower temperature range for photosynthesis than the higher plants. The optimum temperature for photosynthesis for most of the plants is 25 to 35°C. Photosynthesis stops at 40°C in temperate plants and at 50°C in tropical plants

12. Respiration:   The rate of respiration increases with the rise of temperature. It is maximum at optimum temperature. But it decreases rapidly above optimal temperature.

13. General distribution of plants :  Temperature and moisture determine the general distribution of vegetation . Different belts of vegetation occur between the equator and the poles . Vegetation is primarily determined by heat. Thus plants which grow in a hot climate cannot grow in a cold climate and vice versa. Therefore , same crop are not cultivated in all regions of the world. Different crops are cultivated in different region i of the world.

14. Germination of seed :  Temperature also affects the germination of seed. Every seed has optimal temperature. Seed cannot grow below or above this temperature.

15. Spreading of diseases:   Temperature and humidity affects the spreading of plant diseases. Low temperature along with high humidity favours the attack of rust. damping off, seedling blight, foot rot and root rot.

16. Changes in the temperature in the natural environment of plants affect both their functioning and their growth. Maintenance of a relatively stable internal environment is just as important for plant metabolism as it is for animals. Plant Responses to temperature Change

17. Plants respond to changes in light, water availability and temperature. All of which are linked, since heat is often associated with light ( for example , the radiant energy of sunlight) Plant Responses to temperature Change

18. Most Plants have a growth season and life cycle that follow the seasonal temperature variations of their environment. Plant Responses to temperature Change

19. Low availability of water may also be associated with very cold temperatures, since frozen water (ice and snow) is not available for use of plants. Plant Responses to temperature Change

20. Temperature above 40* C may cause damage to proteins and those above 75* C to chlorophyll pigment within the plant. Since plants can not move into the shade , they tend to have stronger physiological and structural adaptations. Plant Responses to temperature Change

21. Adaptations to extreme https://r7---sn-2uja-aix6.googlevideo.com/videoplayback?upn=H4OKKVs8Tb8&sparams=clen%2Cdur%2Cei%2Cgir%2Cid%2Cinitcwndbps%2Cip%2Cipbits%2Citag%2Clmt%2Cmime%2Cmm%2Cmn%2Cms%2Cmv%2Cpl%2Cratebypass%2Crequiressl%2Csource%2Cupn%2Cexpire&expire=1491164648&lmt=1393068115626652&ratebypass=yes&ip=39.52.101.115&clen=9249381&ms=au&mv=m&mt=1491142946&dur=193.654&id=o-AKSamtanRpU0Bk1CpVo9d8Ez8PGfbMuME8AEDmodRnva&mn=sn-2uja-aix6&gir=yes&mime=video%2Fmp4&signature=9DCAB1AB78B9C6E9FD612E7711546BDF45D2B21F.D208DB4942804FB08452D07B8C301276E0FD7172&mm=31&requiressl=yes&ei=iAnhWPHHJoWdcO6DtdAK&itag=18&source=youtube&pl=17&ipbits=0&initcwndbps=166250&key=yt6 Video link..

22. Reflective leaf surfaces that reduce the amount of radiation absorbed can help keep a plant cool in hot conditions. Leaves may be light or silvery coloured , or have waxy or shiny surfaces. Physiological and Structural adaptation

23. Evaporative cooling - loss of water via transpiration (stomata opening ) in order to evaporate and have a cooling effect on the plant. This decreases internal temperature , however water is not readily available . This can kill the plant. Physiological and Structural adaptation

24. Hot areas are often dry, comprising evaporative cooling. A plant needs to strike a fine balance between the risks of excess water loss during cooling versus heat build-up during water conservation. Plant responses to Temperature change

25. Wilting - Some plants can wilt during the day instead, which decreases surface area of flowers/leaves to the sun.  If water is readily available, this is temporary. If water not available, this can lead to the death of the plant. For example, roses. Plant Responses to temperature Change

26.   Leaf orientation – Plants change the orientation of their leaves to decrease the surface area exposed to the sun at the hottest part of the day. Most eucalypts hang vertically to reduce their exposure to the hot sun Physiological and Structural adaptation

27. Plants responding to excessive temperature like fires, may die, (especially non woody plants), however they leave dormant seeds, with thick protective seed coats. Seed dispersal in some Australian plants is stimulated by the extreme heat of fire. Physiological and Structural adaptation

28.  Banksia , Hakea and some Eucalyptus plants bear fruits with hard woody cases that are not dropped from the parent plant. The heat of a fire stimulates the fruits to open, and the seeds are released. Physiological and Structural adaptation

29. Some of these seeds need fire as a trigger to germinate (begin to grow a seedling). Or some plants may die above ground leaving roots, rhizomes, bulbs or tubers to survive underground. When favorable conditions return, these sprout Physiological and Structural adaptation

30.   Leaf fall in Summer . Eucalypts are evergreen trees that drop some of their leaves during the dry season in hot climates to reduce the surface area exposed to absorb heat. This also reduces the risk of losing too much water by transpiration.  Physiological and Structural adaptation

31. Temperature is one factor that controls developmental changes in a plant’s life cycle, from germination through to flowering and seed dispersal. In Australia, too high a temperature during flower formation produces a poor wheat crop, because pollen formation is very temperature-sensitive. Physiological and Structural adaptation

32.   Leaf fall in autumn (deciduous trees) Many trees lose their leaves during autumn and the cold winter months when resources (for example the sun and water) are not as readily available. Plant responding to cold temerature

33. It allows them to survive not only the extremely low temperatures, but also the water shortages and lower availability of sunlight. For example, the beech tree found in Tasmania Plant responding to cold temerature

34.   Organic anti-freeze – Normally, in cold conditions, water between cells freezes first posing the greatest risk of damage for plants. Some plants that live in extremely cold conditions produce anti-freeze substance that reduces the temperature at which the cytoplasm or cell sap freezes. Plant responding to cold temerature

35. Frost during periods of new growth may damage plants, but many plants have leaves that are frost-tolerant. For example, after frost the leaves of camellias appear semi-transparent, but on thawing return to normal.  Plant responding to cold temerature

36. Plants may alter their growth rate, active plant growth can occur within the range 5°C-45°C or in tropical areas, growth may cease below 15°C. Plant responding to cold temerature

37. Vernalisation some plants flower in response to low temperatures for example, tulip bulbs must be exposed to between 6 weeks and 3 months of intense cold before they will flower. Plant responding to cold temerature

38. Australian gardeners often mimic this effect by removing tulip bulbs from the ground in winter and storing them in the refrigerator, before replanting them in spring, to ensure that they will flower. Plant responding to cold temerature

39. Plants must also maintain a relatively stable internal environment. Since plants cannot move - they tend to have stronger physiological and structural adaptations. For heat some adaptations include wilting and dropping leaves. For cold some include: frost tolerance and being deciduous. Summary