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Regulation of root system architecture

Regulation of root system architecture. Root system architecture refers to the organization of the roots as determined by the degree of root branching. Branching allows for root system proliferation to promote nutrient and water acquisition

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Regulation of root system architecture

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  1. Regulation of root system architecture • Root system architecture refers to the organization of the roots as determined by the degree of root branching. Branching allows for root system proliferation to promote nutrient and water acquisition Root system architecture is influenced by water availability and nutrients (particularly N and P) Biology 751

  2. Root system architecture is plastic and influenced by the environment • In response to drought stress root elongation is maintained & LR formation is suppressed • This favours growth towards new soil environments • When roots are in better soil environment root proliferation (branching) occurs • ABA accumulates in the roots of drought-stressed plants and plays a role in maintaining growth. Biology 751

  3. ABA regulation of LR formation • ABA is a negative regulator of LR formation • Exogenous ABA inhibits LR emergence prior to activation of the LR meristem • Auxin and ABA are believed to interact during LR development • ABA mediates the ability of nitrate to inhibit LR development Biology 751

  4. ABA maintains root growth in water deficit stressed seedlings • Wild type and ABA-deficient seedlings were transferred to a low or high Yw growing medium • Growth was measured • In roots: • At low Yw the ABA-deficient mutant roots grew less than WT roots • ABA is involved in maintaining root growth at low Yw • ABA promotes osmotic adjustment in the root meristem • Maintains cell division and expansion • Changes in the cell wall (loosening) aid growth Biology 751

  5. ABA reduces shoot growth in water deficit stressed seedlings • Recall that in the shoot ABA inhibits growth: • The shoot of ABA-deficient seedlings grew more under low Yw than WT seedlings • ABA inhibits shoot growth in low Yw plants • Adaptive significance: • Increases root:shoot ratio in water deficit-stressed plants • Increases vol. of soil that can be explored for water uptake Biology 751

  6. Maize seedlings growing at low Yw From Spollen et al., Plant Phys. 122:967 (2000) ABA maintains root growth by suppressing ethylene production • FLU (fluridone) is an inhibitor of ABA biosynthesis • AOA, AVG & STS are inhibitors of ethylene action or biosynthesis • Inhibiting ethylene production or action in ABA-deficient seedlings restored growth in water deficit stressed seedlings • ABA suppresses ethylene production and thereby maintains root growth Biology 751

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