Uptake and translocation Calcium ions are not transported effectively y the symplast. The typical pathway for b Ca2+ uptake of involves initial movement into the free space of the root apoplast and then further movement through apoplastic pathways The movement of Ca2+ in the xylem vessels can not be explained simply in terms of mass flow as Ca 2+ is absorbed by adjacent cells and also absorbed to indiffusible anions in the xylem walls The cell wall is as reservoir for supply to acropetal 向顶的) growing centre
Uptake and translocation ◼ Calcium ions are not transported effectively by the symplast. The typical pathway for Ca2+ uptake of involves initial movement into the free space of the root apoplast and then further movement through apoplastic pathways. The movement of Ca2+ in the xylem vessels can not be explained simply in terms of mass flow as Ca2+ is absorbed by adjacent cells and also absorbed to indiffusible anions in the xylem walls. The cell wall is as reservoir for supply to acropetal (向顶的)growing centre
Uptake and translocation In growing plants Ca2+ is translocated preferentially towards the shoot apex even though the transpiration rate here is much low lower than in the older leaves The rate of Ca2+ downward of plant is very low due to the fact that ca2+ is transported in only very small concentration in the phloem, tissues supplied by the phloem sap (such as fruit) has less Ca+ than leaves Once it is deposited in older leaves it cannot be mobilized to the growing tips
Uptake and translocation ◼ In growing plants, Ca2+ is translocated preferentially towards the shoot apex even though the transpiration rate here is much low lower than in the older leaves. ◼ The rate of Ca2+ downward of plant is very low due to the fact that Ca2+ is transported in only very small concentration in the phloem, tissues supplied by the phloem sap (such as fruit) has less Ca2+ than leaves. ◼ Once it is deposited in older leaves it cannot be mobilized to the growing tips
1: 2nd Root segment. 3 cm 3rd Root segment. 4th Root 17 5th Root segment, 3 cm 6th Root segment, 3 cm ca-45 Treated segment, 3 cm 2nd Lower segment, 3 cm Fig. 11.4 Distribution of Ca-45 in a maize seedling following application to a specific of the root (after MARSCHNER and RICHTER [1974))
The factors affecting calcium uptake 1. The other cations such as K and NH4 2. Transpiration steam Calcium transport controlled by humidity Blossom end rot caused by drought water logged soil high salt concentration poor aeration low temperature
The factors affecting calcium uptake 1. The other cations such as K+ and NH4 + 2. Transpiration steam Calcium transport controlled by humidity Blossom end rot caused by drought, water logged soil, high salt concentration poor aeration low temperature
The forms of calcium in plant Free Ca2+ Absorbed ca 2+ by carboxylic phosphoryl(磷酰基) and pheno|ic hydroxyl groups Precipitated as Ca oxalate, carbonate and phosphate in vacuoles, or pectins n cell walls, or phytate in seed Calcium ions are also bound to membranes
The forms of calcium in plant ◼ Free Ca2+ ◼ Absorbed Ca2+ by carboxylic, phosphorylic(磷酰基) and phenolic hydroxyl groups. ◼ Precipitated as Ca oxalate, carbonate and phosphate in vacuoles, or pectins in cell walls, or phytate in seed. ◼ Calcium ions are also bound to membranes