Degree Type

Dissertation

Date of Award

1992

Degree Name

Doctor of Philosophy

Department

Agronomy

Major

Ecology and Evolutionary Biology

First Advisor

S. Elwynn Taylor

Abstract

In order to understand the mechanism of water use and drought resistance of corn, it is necessary to study effects of these characteristics on water use and drought resistance and to be able to quantify the effects. Two corn hybrids, Pioneer 3343 (P3343) and Pioneer 3379 (P3379) known as drought sensitive and drought resistant, respectively, with a sorghum hybrid, Pioneer 8086 (P8086) as control, were investigated. Our study included measurements of leaf resistance, total plant leaf area, plant height, root weight, and plant water potential and permanent wilting points of soil water content. Experiments were conducted in the greenhouse, growth chamber, and field over a three year period;The field and greenhouse results show that P3379 had greater total plant leaf area, and higher transpiration rates but shorter plant height. The P3379 had the lower permanent wilting point (soil moisture content), and higher water consumption than P3343 in greenhouse experiments. However, there were no differences in soil moisture and grain yield in the field studies. If P3379 is considered to be drought resistant plant, it may be characterized as a water spender that can resist mild drought because it has more available water from its lower permanent wilting point that may result in lower leaf resistance;A computerized model was developed to evaluate plant water use in terms of physiological, morphological and phenological features. The model includes simulation of temperature and vapor profiles in a corn canopy, radiation penetration in the canopy, and development of leaf area index and plant height. The inputs for the model include daily and hourly weather data, maximum plant leaf area, planting date, silking data, maturity date, and planting density. Outputs are daily transpiration, daily plant water use, cumulative water use, total plant leaf area and leaf area index;The validation study indicated that the calculated plant water use and leaf area development agree well with measurements. The sensitivity study showed that plant total leaf area significantly influenced plant water use, especially when leaf area index was low. Increase of leaf area with a fixed planting density would increase plant water use in a growing season. The effect of silking date on plant water use was not as significant as leaf area. However, silking date is an indicator of plant water use. (Abstract shortened by UMI.)

DOI

https://doi.org/10.31274/rtd-180813-7430

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

Hanzhong Zhang

Language

en

Proquest ID

AAI9311546

File Format

application/pdf

File Size

110 pages

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