UBC Theses and Dissertations

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UBC Theses and Dissertations

The effect of some environmental factors upon the CO₂ exchange and the effect of photoperiod upon the development of Hordeum vulgare L. Hubbard, William Frederick


Experiments were conducted with a Blue M "Vapor-Temp" controlled environment apparatus to show the effect of temperature, light intensity, relative humidity and age upon the rate of CO₂ exchange for twelve barley varieties. All varieties showed an increase in CO₂ uptake with an increase in temperature to a certain optimum, varying with variety. When the temperature was raised above this point, the rate of CO₂ uptake decreased. In all varieties tested the rate of CO₂ uptake increased as light intensity was increased up to 2400 ft. candles. Three out of four varieties tested showed significant changes in rate of CO₂ uptake with changes in relative humidity. All varieties tested showed an initial decrease in rate of CO₂ uptake per unit leaf area as the plants aged from 15 to 30 days. Above this age there was little change in rate of CO₂ exchange. Experiments were also conducted in photoperiod chambers to determine the developmental response of different barley varieties to different photoperiods. It was found that the varieties differed in overall response to photoperiod. Within a variety there was a difference in rate of development between plants subjected to different photoperiods. The optimal photoperiod for head differentiation and for head appearance was 21 or 24 hours for all varieties.

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