National Academies Press: OpenBook

Physiological Limitations on Crop Production Under Temperature and Moisture Stress (1969)

Chapter: 'Plant Growth under Temperature Extremes'

« Previous: 'General Aspects of Food Production Problems'
Suggested Citation:"'Plant Growth under Temperature Extremes'." National Research Council. 1969. Physiological Limitations on Crop Production Under Temperature and Moisture Stress. Washington, DC: The National Academies Press. doi: 10.17226/21254.
×
Page 5
Suggested Citation:"'Plant Growth under Temperature Extremes'." National Research Council. 1969. Physiological Limitations on Crop Production Under Temperature and Moisture Stress. Washington, DC: The National Academies Press. doi: 10.17226/21254.
×
Page 6
Suggested Citation:"'Plant Growth under Temperature Extremes'." National Research Council. 1969. Physiological Limitations on Crop Production Under Temperature and Moisture Stress. Washington, DC: The National Academies Press. doi: 10.17226/21254.
×
Page 7
Suggested Citation:"'Plant Growth under Temperature Extremes'." National Research Council. 1969. Physiological Limitations on Crop Production Under Temperature and Moisture Stress. Washington, DC: The National Academies Press. doi: 10.17226/21254.
×
Page 8
Suggested Citation:"'Plant Growth under Temperature Extremes'." National Research Council. 1969. Physiological Limitations on Crop Production Under Temperature and Moisture Stress. Washington, DC: The National Academies Press. doi: 10.17226/21254.
×
Page 9

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

4 GENETIC BASIS OF CROP RESISTANCE TO ENVIRONMENTAL STRESS Oscar Brauer H., Escuela Nacional de Agricultura, Colegio de Postgraduados, Chapingo, Mexico Environmental stresses are often the most limiting factor for crop production. Plants may escape, tolerate, or resist factors like cold, heat, drought, or soil salinity by means of genetic differences. Most remarkable inherited differences are found among different species of plants. Plants of the genus Opuntia may produce a good crop of forage or fruits or both under arid and semiarid conditions. Obtaining thornless plants and increasing their nutritive value are breeding goals partially achieved already. Selection of maize for drought and cold tolerance led to finding Michoacan 21, compuesto 101-4, later called "latente." When plants of this strain are subject to drought stress, they stop growing; and when water is again available several days later, they continue growing to a more or less normal size and produce a good crop. Under the same conditions most other strains of maize stop growing, roll their leaves, and differentiate a flower stalk. They are then unable to continue growing, and the yield of corn is very low. Michoacan 21 has been used as parent stock for H.28 a hybrid that grows very efficiently unper low rain conditions and that also has con- siderable resistance to cold damage. Finding a plant species or variety that will produce a crop under environmental stress is one of the most efficient means of increasing food production.

5 Plant Growth under Temperature Extremes THE PHYSIOLOGICAL PROBLEMS OF POTATO CULTURE AT COOL TEMPERATURES* C. Ochoa, Universidad Agraria, Lima, Peru Dr. Ochoa stressed the fact that low nighttime temperature (-3.5° to -5° C) is the main problem of potato production in Andean culture. He believed that great strides could be made through plant breeding by incorporating frost resistance characteristics from several low-yielding native species. * Prepared from notes made by E. R. Lemon.

6 THE PHYSIOLOGY AND GENETICS OF HEAT TOLERANCE E. J. Kinbacher, Department of Horticulture and Forestry, University of Nebraska Heat tolerance is the ability of plants to survive high cellular temperatures. Additional knowledge of the basic physiology of heat tolerance is needed before a detailed genetic understanding can be ob- tained. Control of relative humidity is essential in heat tolerance re- search. At a given temperature, injury is directly related to relative humidity. In some of our tests we doubled the degree of injury as we increased relative humidity from 50% to 75% and from 75% to 100%. Air temperature was 43° C during these 8-hour heat tests. Our data from plants subjected to high temperatures (55° to 60° C) at low relative humidities for several hours indicate that when the plant tissue reaches a specific temperature, injury occurs. The same temperature injures plants in 100% relative humidity tests. In the last 10 years, heat hardening by exposure to high tempera- tures has become an accepted phenomenon. Heat hardening permits studying heat tolerance with plant material of the same genetic back- ground. One theoretical explanation of heat tolerance is that heat-tolerant organisms have thermostable enzymes and proteins. In our laboratory, my colleague Charles Y. Sullivan and I collected data that support this theory by using purified fractions of malic dehydrogenase (MDH) and fraction I protein. Heat hardening increased the thermostability of MDH and fraction I protein. Therefore, one way that heat hardening may increase heat tolerance is by increasing the thermal stability of en- zymes and proteins. A possible summary of the heat-hardening process is the following: Step 1. Small changes occur in existing proteins that increase their stability (i.e., intramolecular rearrangement of SS-bonds). Step 2. Hydrolysis of existing proteins occurs. Step 3. Environmental factors stimulate DNA to produce a different type of RNA. Step 4. The new RNA results in the synthesis of heat stable pro- teins.

7 Development and standardization of screening or testing procedures are important in heat-tolerance research. In our laboratory, we use a leaf-disc-heat test to determine the heat tolerance of plant material. This procedure is a modification of Dexter's electrical conductivity test. Excellent correlation was obtained between data from our leaf- disc-heat test and data obtained by dipping entire plants in hot-water baths. We have ranked varieties tested for MDH therrnostability and decline in respiration rate at high temperatures. Poor correlation was obtained between these procedures and the leaf-disc-heat test. Alexandrov studied a number of criteria for testing heat injury. The temperature that caused injury to the cells varied with the criterion of injury employed. Injurious temperatures was between 20° and 30° c, the temperature depending on the plant material used. Research on heat tolerance of plants is being conducted few laboratories on a worldwide basis. Since heat tolerance tant in crop production, more research should be conducted. lowing areas should be investigated: in only a is impor- The fol- 1. The molecular structure of proteins associated with heat tolerance. 2. The effect of heat on intact organelles, chloroplasts, and mitrochondria. 3. The effect of heat on photosynthesis and respiration. (What effect does a few hours' exposure at 43° to 45° C have on photosynthesis and respiration rate for the next 24 to 48 hours?)

8 THE BASIS FOR RESISTANCE OF PLANTS TO SUBFREEZING TEMPERATURES H. F. Hodges, Department of Agronomy, Purdue University Three types of injury occur in plants subject to subfreezing tem- peratures. 1. Certain plants subjected to subfreezing temperatures have been found to contain a high molecular weight polysaccharide that acts as a natural inhibitor to ice formation in the tissue. This polysaccharide appears to interfere with the development of ice crystals at the solid- liquid interface and causes a slushlike ice to form in the tissue in- stead of the more destructive "perfect" ice crystals. 2. Protoplasmic factors determine survival when histological dis- ruption is not a lethal factor during freezing. Water in bulk form develops clusters of icelike organization for brief intervals at tem- peratures well above 0° C. These flickering clusters closely resemble ice in organization, and their longevity is proportional to temperature. Apolar molecules cause additional structuring via the formation of hydrogen bonds. It has been proposed that sugars and portions of the protein and lipid molecules in the cell have protective water lattices that prevent denaturation by dehydration during freezing. 3. A third type of injury that occurs during freezing is the dis- ruption of crucial membranes. Oxidative phosphorylation in mitochondria and photophosphorylation in chloroplasts have been uncoupled during freezing. Photophosphorylation uncoupling is closely associated with disruption of the membrane. The freezing patterns and the nature of water redistribution during freezing, in relation to the development of frost resistance in plants, indicate that the genetic control of cold hardening is very complex and can probably be studied effectively only by separating the total problem into the genetic control of the individual components of frost resistance.

Next: 'Drought' »
Physiological Limitations on Crop Production Under Temperature and Moisture Stress Get This Book
×
MyNAP members save 10% online.
Login or Register to save!
Download Free PDF
  1. ×

    Welcome to OpenBook!

    You're looking at OpenBook, NAP.edu's online reading room since 1999. Based on feedback from you, our users, we've made some improvements that make it easier than ever to read thousands of publications on our website.

    Do you want to take a quick tour of the OpenBook's features?

    No Thanks Take a Tour »
  2. ×

    Show this book's table of contents, where you can jump to any chapter by name.

    « Back Next »
  3. ×

    ...or use these buttons to go back to the previous chapter or skip to the next one.

    « Back Next »
  4. ×

    Jump up to the previous page or down to the next one. Also, you can type in a page number and press Enter to go directly to that page in the book.

    « Back Next »
  5. ×

    To search the entire text of this book, type in your search term here and press Enter.

    « Back Next »
  6. ×

    Share a link to this book page on your preferred social network or via email.

    « Back Next »
  7. ×

    View our suggested citation for this chapter.

    « Back Next »
  8. ×

    Ready to take your reading offline? Click here to buy this book in print or download it as a free PDF, if available.

    « Back Next »
Stay Connected!