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mlativi nowm*ri UMinunv icali) 124 CHAPTER 8 . ' -1965 'Guide And Data Boole optimum' conditions during all stages of development! How ever, the optimum temperature is related to other environ mental factors4*-0 and may be altered by changes in' water relations, light intensity, etc. Controlledenvironment facilities to study specific problems such `as- lethal' temperatures or transpiration' and evaporation of water may require tempera tures as high'as 110 F. Studies of dormancy, vernalization^ and winter hardiness require temperatures of -- 60 to +'50 F, and termination studies require temperatures from 35 to 95 F. However, most plants are grown in' controlled environment chambers at temperatures betWeeh'50 and 80'F, frequently the light and dark period temperatures differing by 10-15 Fdeg. Many investigators, afterpreliminary'experimentation; settle upon one temperature regime and seldom change it.' ' Dry-bulb temperatures may be misleading: The leaf dr soil temperature is significantly higher under' sunlight of incaq^ descent light than under fluorescent light with , equal`footcandle readings. The effect of temperature fluctuations on plants is a func tion of the magnitude-and the frequency of-the variations. Little detailed information b available on the effect of the. rise of the temperature differential froth the control'point when the cycles are relatively rapid. However, each biok>gical investigator should have some indication of the temperature variance allowable for his particular studies, and will specify, his requirements. Humidity Very, low or very high humidity has a marked effect oh plant growth by influencing secondary factors, such as making the plant more susceptible'to"diseascs by providing a.better' environment for pathogenic organisms. Many existing con- trolled-environment rooms maintain 55 to 65 percent relative humidity-at 70`to 75 F, without any attempt to oontrol-hu- midity.:'Since-'plants-must be watered" one or more times daily, the relative humidity in some rooms will rise to 90 or 95 percent for a brief period following theapplicationof water to the plants. * " i- ' ': Wind ; .. ' Wind velocity influences .many fetors that affect plant growth, such as transpiration^ evaporation' of water from the Boil, and availability of CO*.As a result, leaf rise, intemode length, and'other, aspects of.plant growth may be"altered. However, wind direction itself does not' seem to .be important (Fig.^17). V' ' '* . The -biologist usually, prefers a minimum amount of leaf movement,'.but. he will 'usually. have to, compromise and permit'some leaf movement, to obtain the air velocity, neoes^ sary- to maintain the desired temperature. Air speeds of 50 to 150 fpin in.an empty chamber'are usually considered reason-' able! When pots containing plants occupy half the bench area, air directed .upward through the bench and between the pots will have about double.the velocity of air pasting through an empty bench. , , , . .. .,. Plant variance at various positions in' the chamber may be the result of differences in mnd velocity. Soil' evaporation Leaves*0! 18.... Photosynthesis of a Cucumber Leaf at a 'limiting and Saturating CO* Concentration Under! Incandescent' Light1* .Environmental Control for Animals and Plants--Physiological Considerations 125 and temperature, leaf transpiration and temperature,' am bient air temperature, and relative humidity are all nffocfoA by air velocity. Since one of the reasons advanced for the,use of controlled environment facilities is to reduce such position .variance,' uniform air flow over the growing area is a major <fesigo factor. Air Composition Efforts are currently being made to control the composition of the air in plant growth chambers. Smog, industrial fumes, and radioactive materials are being studied, and the effects of jtuvfswtging the CO* content of the controlled environment room atmosphere are receiving special attention.8 In the photosynthetic process, plants absorb CO% which mtApf, up about 0.03 to 0.04 percent of the normal air, through frpnll openings in the leaves called stomata. The amount of CO* required for maximum plant growth depends upon the stage of growth, leaf area, light intensity, temperature, wind velocity past the stomatal opening, and a number of other factors. The rate of photosynthesis is usually limited by the low concentrations of CO*. It has been shown experimentally that an increase of normal atmospheric CO* from 0.03 to 0.13 percent causes a corresponding increase in the photosynthetic rate, and that the increase obtained depends on the tempera ture (Fig. 18). REFERENCES 1 R. G. Yeck and R. E. Stewart: A ten-year summary of the peychroenergetie laboratory dairy cattle research at the Univasty of Misouri (American Society of Agricultural Engineers Transactions, VoL 2, 1959, p. 71). 11. L. Berry, M. D. Shanklin, and H. D. Johnson: Dairy shelter design based on milk production decline aa affected by temperature and humidity (American Society of Agricultural Engineers Transactions, Vol. 7, 1964). * R. G. Yeck: &a6fe Heat and Moisture Dissipation with Beef Caber at Temperatures of 60 and 80 F (Missouri Agricultural Ex periment Station Research Bulletin No. 645, October 1957). * R. G. Yeck and R. E. Stewart: Stable Heat and Moisture Dissipation with Dairy Calces at Temperatures of 60 and 80 F (Missouri Agricultural Experiment Station Research Bulletin No. 759, November 1960). * H. D. Johnson, A. C. Ragsdale, and R. G. Yeck: Effects of Constant Environmental Temperature of 60 F and 80 F on the Feta and Water Consumption of Brahman, Santa Gertrudis, and Short hpm Calces During Growth (University of Missouri Agricultural Experiment Station, Bulletin No. 683, November 1958). * A. C. Ragsdale: Growth Standardsfor Dairy Cattle (University of Missouri Agricultural Experiment Station, Bulletin No. 336, 1 Recommended Nutrient Allowances of Beef Cattle (National Research CoundL Washington, D. C., i960). 1J. G. Ball, cl Branton, and E. J. Stone: Eetma, estrus cycles, ovulation time, time of service and fertility of dairy cattle in i/ouiriana (Journal of Dairy Science, Vol. 42, 1959, p. 1088). * R. W. Phillips and F. F. McKenzie: The Thermoregulatory Function and Mechanism of the Scrotum (Missouri Agricultural Experiment Station Research Bulletin No. 217, 1934). " J- W. Smith et aL: The Effects of Air Movement, Air Movement Fhu Sprinkling and Air Conditioning on Semen Production and Physiological Responses of Dairy Bulls Under Southern Conditions (Louisiana Agricultural Experiment Station, Annual Progress Report, Dairy Department Publication No. 4, 1955). u R. B. Casady, R. M. Myers, and J. E. Legates: The effect of exposure to high ambient temperatures on spermatogenesis in dairy bulla (Journal Dairy Science, VoL 36, 1953, p. 14). " E; J. Warwick: Effects of high temperatures on growth and fattening in beef cattle, hogs and sheep (Journal of Heredity, VoL 49, 1958, p. 69). u N. T. M. Yeatea and J. T. Parer: Chapter 18, Effects of stress on Reproduction (Reproduction in Farm Animals, E. 8. E. Hafez Ed. Lea and Febiger, Philadelphia, 1962). M M. Wodzicka: Seasonal variation in wool growth and heat tolerance in sheep. I. Wool growth (Australian Journal of Agri cultural Research, 1960, p. 75). . " F. Cockrem and G. A. Wichlam: Some preliminaryobeerva tions on factors affecting the temperature of the skin interface of .the New Zealand Romney sheep. (New Zealand Journal of Agri cultural Research, 4, 1961, p. 31). - " R. B. Symington: Studies on the adaptability of three breeds of sheep to a tropical environment modified tty altitude. IV. role of the fleece in thermoregulation in German Merino ewes (Journal af Agricultural Science, VoL 55, I960, p. 311). " D. H. K. Lee: Studies of heat regulation in the sheep with special reference to the Merino (Australian Journal cf. Agricul tural Research, Vol. 1, 1950, p. 200). M C. W. Alltstou, G. E. Egu and L. C. Ulberg: Loss of potential young in the ewe due to high ambient temperature (Journal of Applied Physiology, VoL 18, 1961, p. 253). 11 R_ H. Dutt and P. T. Hamm: Effect of exposure to high en vironmental temperature and shearing on semen production of rams in winter (Journal Animal Science, Vol. 16, 1957, p. 328). ** C. V. Hulet, El-Sheikh, A. L. Pope, and L. E. Caaida: The effects of shearing and level of feeding on fertility of rams (Journal Animal Science, Voi 10, 1951, p. 907). n R. H. Dutt: Temperature end light as factors in reproduction in farm animals (Journal Dairy Science, Vol. 43 (euppl.) 1960, p. 123). "L C. Ulberg: The influence of high temperature on repro duction (Journal cf Heredity, Vol. 49, 1958, p. 62). " N. T. M. Yeates: The effect of high air temperature on reproduction in the ewe (Journal Agricultural Science, Voi 43, 1953, p. 199). ** N. T. M. Yeates: Foetal dwarfism is sheep--an effect of high atmospheric temperature during gestation (Journal Agricultural Science, Voi 51, 1958, p. 84). " G. Alexander: Temperature regulation in the new born lamb. V. Summit metabolism (Auetralian Journal tf Agricultural Research, 13, 1962, p. 101). * D. G. Armstrong et al: Heat production and heat emission of two breeds of sheep (Journal of Agricultural Science, VoL 55, I960, p. 395). n D. G. Armstrong et al: Theeffect of environmental conditions of food utilisation by sheep (Animal Production, Voi 1, Part 1, March 1959, p. 1). 11 T. E. Hazen and D. W. Mangold: Functional and basic re quirements of swine housing (Agricultural Engineering, Voi 41, September 1960, p. 585). " T. E. Bond, C. F. Kelly, and EL Heitman, Jr.: Effect of diurnal temperature on beat loss and well-being of swine (ASAE Transactions, VoL 6, 1963, p. 132). * L. E. Mount: Food, meat and heat conservation (Pig In dustry Development Authority Conference, Circular, Buxton, Derttyshire, England, April 1963). " P. H. Sorensen ana J. EL Moustgaard: Der F.inflmw der Stallklimas auf das Wachstum die Futterverwertung und Slschtqualitat von Schwernen (Schlusbericht VIII International Tierzuchtkongres, Hamburg, 1961, p. 27). " R, I. Lipper and R. J. McGinty: Cooled breathing air for sows (ASAE Transactions. VoL 4,1961, p. 8). 43 T. E. Bond, H. Heitman, Jr., and C. F. Kelly: Effects of in creased air velocities on heat and moisture loss and growth of swine (ASAE Paper No. 63-901, December 1963). ** T. E. Bond, C. F. Kelly, and H. Heitman, Jr.: Hog house air conditioning and ventilation data (ASAE Transactions, Voi 2, 1959, p. 1). * H. Ota and E. H. McNally: Poultry Respiration Calorimetric Studies cf Laying Hens (U. S. Department of Agriculture, ARS 42-43, June 1961). m J. R. Hawes, W. Grub, and C. A. Rollo: Hie effects of high constant environmental temperatures upon caged white Leghorn pullets (Journal qf Poultry Science, May 1961, p. 1416). n W. J. Mueller: The effect of constant and fluctuating environ mental temperatures on the biological performance of laying pullets (Journal cf Poultry Science, June 1961, p. 1562). ** L. N. Drury: The Effect of Air Velocity on Broiler Growth in a Dtumally Cycling Hot Humid Environment (Unpublished MS Thesis, University of Georgia, 1961). ** D. J. C. Friend, V. A. Helson, and J. E. Fisher: The influence of the ratio of incandescent to fluorescent light on the flowering response of Marquis wheat grown under controlled conditions (Canada Journal of Plant Science, Vol. 4L 1961). * C. E. Weits: Lamp Bulletin, LD-1 (General Electric, Cleve land, Ohio. 1950). 41 A. Hotlender: Radiation Biology, VoL 3 (McGraw-Hill Book Co., New York, 1956). H. A. Bortnwick and S. B. Hendricks: Effects of radiation on growth and development (Handbuch der Pflanzenphysiologie, VoL 16, 1961, p. 299).