Degree

Doctor of Philosophy (PhD)

Department

School of Plant, Environmental, and Soil Sciences

Document Type

Dissertation

Abstract

Horticultural container production heavily relies upon porous soilless substrates to mass produce specialty crops. Soilless substrates are responsible for continuously maintaining optimal water, mineral nutrients, and air balances to promote healthy root growth and support productive shoot yield (foliage or fruit). Increasing evidence of substrate research continues to highlight the strong relationships associated with root development and substrate physiochemical properties. Despite the importance of the root system for overall plant health, most horticultural research to-date has focused on shoot development. Research tends to report total root biomass as the primary root-growth metric; however, this results in several developmental features becoming inherently lost. For instance, root morphology (surface features) and architecture (spatial configuration) can provide more fine-tuned information on how conventional or engineered (i.e., stratification-layering different substrates; bark screening) substrates impact root development and performance. The research herein involved developing a stronger understanding of how container-grown roots impact soilless substrate dynamic properties, as well as how conventional or engineered substrates modifies root development. Moreover, this dissertation assessed how substrate hydraulic properties and root: shoot development influence plant performance (via predictive modeling) and root uptake (via spectral measurements). In a broad sense, plants grown in either a (1) stratified substrate consisting of fine bark layered over coarse bark or peat-lite layered over pine bark, or (2) finer-textured bark particles, generally contained greater morphological development with regards to total root length, finer root development, and associated root system volume and surface areas. Furthermore, stratified-grown plants typically had wider root architectures, exploring the substrate volume more efficiently and residing longer in the top strata than conventionally-grown plants. Research herein has shown that stratified substrate systems have greater moisture balances and oxygen supply to the rhizosphere, likely explaining the augmented root development. Plants grown in substrates with better pore connectivity and water transfer properties were (1) predicted to have greater physiological performance when growing conditions become harsh (dry rhizosphere and atmosphere) and (2) contain greater local moisture depletion in the rhizosphere, alluding to more uptake capabilities. In all, this dissertation advances scientific methods in measurements for horticultural research to better understand container root-substrate interactions.

Date

10-28-2024

Committee Chair

Fields, Jeb

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Horticulture Commons

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