西北农林科技大学：《植物营养学》课程教学资源（PPT课件讲稿，英文版）Chapter 02 Plant nutrients uptake and transport Mechanisms

Chapter 2 Plant nutrients uptake and transport Mechanisms

Chapter 2 Plant nutrients uptake and transport Mechanisms

Nutrient uptake steps nutrient ------------------ ■■■■■■■■■■ ■■■■I Movement through soil Cell wall Cell membrane ■■■■幅 unloading vascular tissue Cell to cell transport (plasmodesmata

Nutrient uptake steps nut Movement through soil Cell wall Cell membrane unloading vascular tissue Cell to cell transport nutrient (plasmodesmata )

THE CELL WALL Before traversing the plasma membrane(p. m), ions must first cross bulk flow of soil solution couls the cell wall and contact the p The theoretically carry inorganic ions into the cell wall and through the apoplastic athway. the thickness of a cell wall is in the range of 500 to 1000 nm it is orous

THE CELL WALL • Before traversing the plasma membrane (p.m.), ions must first cross the cell wall and contact the p.m. The bulk flow of soil solution could theoretically carry inorganic ions into the cell wall and through the apoplastic pathway. The thickness of a cell wall is in the range of 500 to 1000 nm. It is porous

表1-13一些物质的颗粒直径(毫微米nm) 分子或 水化离 分子或 颗粒离子晶子直径/秘离子晶水化离 体直径 体直径子直径 葡萄糖089 Mq2013092 0190.60Ca2+0.20088 K 027053 cr- 0.36050 NH40.30054NO30.41 Compared to cell walls(500-1000nm) the nutrient ions or molecular are very small

表1-13一些物质的颗粒直径（毫微米nm） 颗粒 分子或 离子晶 体直径 水化离 子直径 颗粒 分子或 离子晶 体直径 水化离 子直径 葡萄糖 0.89 Mg2+ 0.13 0.92 Na + 0.19 0.60 Ca2+ 0.20 0.88 K + 0.27 0.53 CI- 0.36 0.50 NH4 + 0.30 0.54 NO3 - 0.41 Compared to cell walls(500-1000nm), the nutrient ions or molecular are very small

ce|lwa!(细胞壁) The cell wall of parenchyma cells(if 壁细胞) is made up of a middle lamella (M.L.)(胞间薄层), which separated the daughter cells after cell division, and the primary wall(初生壁) which was deposited on to the m l

Cell wall (细胞壁） • The cell wall of parenchyma cells(薄 壁细胞) is made up of a middle lamella (M.L.)(胞间薄层), which separated the daughter cells after cell division, and the primary wall(初生壁） which was deposited on to the M.L

Ce|wal(细胞壁) While the M L is made up of pectic substances(果胶物质), the primary wall also contains hemicelluloses and cellulose pectins(果胶质)α re based on branched chains of a sugar polymer madeψ p of galacturonic acid(半乳糖醛 酸). This is galactose(半乳糖) in which the alcoholic group(崞羟基)atC6is replaced by a carboxyl group(羰基)

• While the M.L. is made up of pectic substances(果胶物质), the primary wall also contains hemicelluloses and cellulose. Pectins(果胶质) are based on branched chains of a sugar polymer made up of galacturonic acid(半乳糖醛 酸). This is galactose (半乳糖)in which the alcoholic group(醇羟基) at C6 is replaced by a carboxyl group(羰基). Cell wall(细胞壁）

Free space Clearly, ionization of carboxyl groups creates a negative charge which makes the cell wall a cation exchange resin. Indeed much Ca2+ is associated with the pectins. In soils with high quantities of free al3+ this toxic ion is bound in large quantities to the cell wall

Free space • Clearly, ionization of carboxyl groups creates a negative charge which makes the cell wall a cation exchange resin. Indeed much Ca2+ is associated with the pectins. In soils with high quantities of free Al3+, this toxic ion is bound in large quantities to the cell wall

ree space Thus when ions enter the cell wal cations can exchange with the cell wal according to their binding affinity typically trivalents>divalents>monovalents Cation exchange capacity(CEC) Anions should not be bound at all

Free space • Thus when ions enter the cell wall, cations can exchange with the cell wall according to their binding affinity :typically • trivalents>divalents>monovalents. • Cation exchange capacity (CEC) • Anions should not be bound at all

cel! membranes(生物膜) Allow for controlled intracellular environment Overton in 1890 demonstrated that penetration of many solutes across the membrane was a function of their lipid solubility. He proposed therefore that the membrane itself was lipid(脂质)

Cell membranes(生物膜) • Allow for controlled intracellular environment • Overton in 1890 demonstrated that penetration of many solutes across the membrane was a function of their lipid solubility. He proposed therefore, that the membrane itself was lipid（脂质）

cel! membranes(生物膜) Unfortunately scientists inferred from this that the permeability(通透性)and diffusion gradient of a substance determined its penetration of the p Most biologically important molecules are not lipid soluble and must penetrate the plasma membrane through proteinaceous transport systems

Cell membranes(生物膜) • Unfortunately scientists inferred from this that the permeability（通透性） and diffusion gradient of a substance determined its penetration of the p.m. • Most biologically important molecules are not lipid soluble and must penetrate the plasma membrane through proteinaceous transport systems