ENLARGED CORTICAL CELLS AND REDUCED CORTICAL CELL FILE NUMBER IMPROVE MAIZE GROWTH UNDER SUBOPTIMAL NITROGEN, PHOSPHORUS AND POTASSIUM AVAILABILITY

Restricted (Penn State Only)
Author:
Yang, Xiyu
Graduate Program:
Horticulture
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
November 15, 2017
Committee Members:
  • Jonathan Lynch, Thesis Advisor
  • Katheleen Brown, Committee Member
  • Armen Kemanian, Committee Member
  • Tom Richard, Committee Member
Keywords:
  • Zea mays
  • Root cortical cell size
  • Root cortical cell file number
  • Root cortical aerenchyma
  • Nutrient acquisition efficiency
  • SimRoot
  • Functional-structural
  • plant model
Abstract:
Studying root systems under edaphic stress is critical for the development of stress tolerant crops. However, it is difficult to study root phenes, their interactions, and performance in different environments via solely empirical approaches, while in silico approaches may provide insights and probe unclear mechanisms. Previous studies showed the presence of reduced cortical cell files (CCFN) and enlarged cortical cells (CCS) in maize roots reduce root metabolic costs. In this thesis, I present a simulation study with SimRoot, a functional-structural plant model, with the goal of testing the hypothesis that CCS, CCFN, and their interactions with root cortical aerenchyma (RCA), may be useful adaptations to limited soil N, P and K availability. Interactions of CCS and CCFN with lateral root branching density (LRBD) and elevated atmospheric CO2 are simulated with limited N, P and K availability. The combination of CCS and CCFN increases the growth of simulated maize up to 105%, 106% or 144% respectively under limited N, P or K availability. Interactions among CCS, CCFN and RCA result in additive benefits of up to 135%, 132% and 161% under limited N, P or K. Under low phosphorus and potassium availability, increased LRBD approximately doubled the utility of CCS and CCFN. The utility of CCS and CCFN is stable as atmospheric CO2 concentration doubled, but decreases as atmospheric CO2 further increased. Our results support the hypothesis that CCS, CCFN, and their interactions with RCA could increase nutrient acquisition by reducing root respiration and root nutrient demand. CCS and CCFN enhance growth via better establishment of the root system and accumulating early stage benefits. Phene synergisms may exist between CCS, CCFN and LRBD. Natural genetic variation in CCS and CCFN may be useful for breeding maize and other crops with improved nutrient acquisition, which is critical for global food security.