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Document Type

Dissertation - University Access Only

Award Date

1991

Degree Name

Doctor of Philosophy (PhD)

Department

Agronomy

First Advisor

Thomas E. Schumacher

Abstract

Phenotypic plasticity (gene by environment interaction) of root systems is one possible mechanism of plant adaptation to nonuniform distribution of soil phosphorous. The purpose of this study was to examine the effects of phosphorous and temperature on the root morphology and P uptake of two maize (Zea mays L.) genotypes that have differences in early growth and phenotypic plasticity. Three studies were conducted using CM37, a genotype with good early growth and high phenotypic plasticity and W153R, a genotype with poor seedling growth and low phenotypic plasticity. The effects of P (5, 45, and 300 mg kg-1) on root morphology and P uptake were examined for the first six growth stages. Subsequent studies examined the effect of soil temperature (15, 20, and 25 °C) and placement of P, on nodal and seminal root morphology. The mechanistic Barber-Cushman nutrient uptake model was used to predict P uptake based on root morphology and P supply characteristics and compared to the observed P uptake. A Maddock (sandy, mixed Udorthentic Haploborolls) soil was used. Phosphorous as NH4H2PO4 was used as the P source. Phosphorous increased root growth and development earlier and to a greater degree for CM37. The formation of lateral roots on CM37 was increased by both temperature and P to a greater extent than on W153R. Fertilizing the nodal root compartment increased root growth and development more than localizing P in the seminal compartment. Phosphorous increased nodal root length more at the highest soil temperature in both genotypes. Phosphorous uptake was more accurately predicted for low soil P levels, nodal roots, and W153R. The ability of root system to respond to differences in soil environments increases the ability of the roots to acquire localized sources of phosphorous. Selecting or breeding genotypes with higher phenotypic plasticity could increase root system response by increasing the formation of roots in a favorable environment thus increasing root surface area and P uptake. This could result in a crop with higher rates of growth and development under less than ideal conditions and thus a higher yield.

Library of Congress Subject Headings

Corn -- Roots
Corn -- Roots -- Effect on temperature on
Plants, Effect of phosphorus on
Corn -- Roots -- Morphology

Format

application/pdf

Number of Pages

169

Publisher

South Dakota State University

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