Document Type

Dissertation - Open Access

Award Date


Degree Name

Doctor of Philosophy (PhD)



First Advisor

Maurice L. Horton


Little information is available on sensitivity of oats to water deficits. Therefore, this study was designed (a) to investigate physiological response of oats to water stress, (b) to determine quantitative effect of water deficits on growth and yield components of oats, and (c) to evaluate plant temperature of oats as a water stress index. Spring oats (Avena sativa L.) grown under field conditions were subjected to 10-11 day stress at boot stage, at anthesis through early grain formation stage and at both stages in combination. Diurnal and seasonal patterns of relative leaf water content, leaf diffusion resistance, and net photosynthesis were examined during the stress period. Relative leaf water content was used as an indicator of water stress level in plants. Severe stress at all development stages studied caused about 80% decline in net photosynthesis. Leaf diffusion resistance exhibited substantial increase with progress of water deficits. Interestingly, earlier stress at the boot stage significantly reduced the sensitivity of photosynthesis to later stress at the anthesis through grain formation stage. Diurnal patterns of these parameters indicated a strong water stress x solar radiation interaction, and the interactions were variable with the stressed and the turgid plants. On rewatering, leaf resistance and relative leaf water content of every stress treatment recovered completely within 1-5 days. However, net photosynthetic rate of the plants stressed at anthesis through early grain formation stage alone showed a more gradual and incomplete recovery than that of the plants stressed at other stages. Leaf area and plant height data showed that at the boot stage leaf and stem elongation was more sensitive to water deficits than net photosynthesis. Stress at the anthesis through early grain formation stage inhibited yield components more severely than stress at the boot stage, especially as shown by panicles, kernels and dehulled kernels data. Earlier stress depressed kernel yield by 20%, whereas the reduction was 58% with the later stress. Stress at both stages in combination produced 67% decrease. After the stress was removed, the plants previously stressed at boot stage exhibited a more active growth than the control plants, as indicated by accelerated photosynthesis and profuse tillering. All stress treatments encouraged a deeper root-system. Leaf and canopy temperature results demonstrated that during clear daylight hours, the stressed oats remained 2-5 C warmer than the unstressed oats. Evidently, canopy temperature can be used to locate water deficits in oats under appropriate atmospheric conditions. Earlier stress did not influence water-use efficiency, however, later stress lowered water-use efficiency based on dry matter production by 33% and that based on kernel yield by 73%.

Library of Congress Subject Headings

Plants -- Water requirements
Oats -- Growth




South Dakota State University