Chapter 3 Nutrient absorbing structures Roots
Chapter 3 Nutrient absorbing structures: Roots
Scope of this lecture Root functions: for plant, soil and ecosystem Root structure and pathways for uptake of nutrients the symplast and apoplast Root architecture(结构) and morphology(形态) Responses of roots and root systems to environmental stress Root hairs and their functions Introduction to combined strategies for efficient nutrient uptake Carbon costs of root processes [if there is timel
Scope of this lecture • Root functions: for plant, soil and ecosystem • Root structure and pathways for uptake of nutrients: the symplast and apoplast • Root architecture(结构)and morphology(形态） • Responses of roots and root systems to environmental stress • Root hairs and their functions • Introduction to combined strategies for efficient nutrient uptake • Carbon costs of root processes [if there is time]
taproot Fibrous root Roots are natural selection's design solution to the problems of obtaining resources from a heterogeneous(异质,多相), porous(多孔的), emi-compressible(半刚性的) medium containing solid, liquid and gaseous phases. (Robinson 1991)
“Roots are natural selection’s design solution to the problems of obtaining resources from a heterogeneous（异质，多相）, porous（多孔的）, semi-compressible（半刚性的） medium containing solid, liquid and gaseous phases.” (Robinson 1991) Fibrous root taproot
Roots and root systems Functions(for plants): 1.Uptake of soil nutrients 2.Uptake of water 3. Storage(e.g. carrots, radish, sugar beet 4 Phytohormone(植物激素) production 5. Habitat for micro-organisms symbiotic N2 fixing bacteria固氮细菌( (internal) mycorrhizal fungi菌根真菌( (internal& externa) rhizosphere根际 bacteria& fungi( external)
Roots and root systems Functions (for plants): 1.Uptake of soil nutrients 2.Uptake of water 3.Storage (e.g. carrots, radish, sugar beet) 4.Phytohormone（植物激素） production 5.Habitat for micro-organisms: - symbiotic N2 -fixing bacteria固氮细菌 (internal) - mycorrhizal fungi菌根真菌 (internal & external) - rhizosphere根际 bacteria & fungi (external)
Roots: a dynamic system 6 days 10 days 17 days Courtesy Mac Kirby CSIRO Land and Water
6 days 10 days 17 days Courtesy Mac Kirby CSIRO Land and Water Roots: a dynamic system
Roots: a dynamic system Width not to scale -Root Epidermal and cortical cells lysed and invaded by bacteria Micro-organisms with microbial and plant mucilages spreading into the sor Cells dividing expanding Sloughed root cap celis Root cap
Roots: a dynamic system Cells dividing & expanding Width not to scale
Roots: a dynamic system -Root Epidermal and cortical cells lysed and invaded by bacteria Main sites of uptake of nutrients& water(根 Micro-organisms with m crobial and 毛区) plant mucilages Cells dividing spreading into the so or meristem expanding or elongation Sloughed root cap celis zne分生区 Root cap 与伸长区
Roots: a dynamic system Main sites of uptake of nutrients & water（根 毛区） Cells dividing or meristem & expanding or elongation zone分生区 与伸长区
Roots and root systems Functions(for plants): Uptake of soil nutrients Uptake of water Storage(e.g. carrots, radish, sugar beet) Phytohormone production Habitat for micro-organisms Anchorage support Many specialised root-ty pes, e.g. aerial roots(from stems or branches) contractile roots(anchor seedlings) cluster roots
Roots and root systems Functions (for plants): • Uptake of soil nutrients • Uptake of water • Storage (e.g. carrots, radish, sugar beet) • Phytohormone production • Habitat for micro-organisms • Anchorage & support Many specialised root-types, e.g. - aerial roots (from stems or branches) - contractile roots (anchor seedlings) - cluster roots
Roots and root systems Functions(for soil ecosystem): Structural stability
Roots and root systems Functions (for soil & ecosystem): • Structural stability
军 Cluster roots簇状根系 套 素学 Lupinus albus Hakea哈克木属 undulata Proteaceae Casuarina木麻黄 属 equisetifolia Banksia拔克西木属 burdett Casuarinaceae Proteaceae
Lupinus albus Hakea哈克木属 undulata Proteaceae Casuarina 木麻黄 属equisetifolia Casuarinaceae Banksia拔克西木属 burdetti Proteaceae Cluster roots簇状根系