Role of roots in root confinement culture of citrus

温州蜜柑的根围栽培是一种较可靠的矮化树势、结出优质果实的方法。该栽培体系的矮化和品质改良机制尚不清楚。本研究的目的是：1)确定根围自由土中干物质和矿质元素的分布，2)限制根的组织学和生理变化，3)阐明植物生长调节剂在顶端和根生长之间存在的关系。在3种土壤体积上种植的三叶柑橘，随着土壤体积的减小，营养生长更加缓慢。在根围处理中，冠根比、细根/总根比值增加，矿质元素含量降低。根限制自由条件下，大叶树叶片水势迅速降低。封育树的导水率、蒸腾速率和TTC还原活性降低，细根皮层比例较高。这些结果表明，根围对果实品质的矮化和改善可能与根系的组织学和生理变化有关。嫁接18个月后，健壮砧木顶端干物质含量最大。在新梢和须根中测定了内源IAA和ABA。健壮砧木的IAA含量最高，矮化砧木的ABA含量最高。根中的含量还不清楚。健壮的砧木在新梢中的Th和IAA/ABA比值最高。

Root confinement culture of satsuma mandarin is a more reliable way of dwarfing tree vigor and producing high quality fruits. The mechanisms of dwarfing and improvement of quality with this culture system were not yet defined. The objectives in this studies were to 1) identify distribution of dry weight and mineral elements in the root confinement frees, 2) histological and physiological changes of confined roots, and 3) clarify the relationship existed between top and root growth by plant growth regulators.In trifoliate orange grown in 3 soil volumes, vegetative growth was more retarded as soil volume were smaller. In the root confinement trees, ratio of shoot to root, and fine root to total root were increased but the content of mineral elements were decreased. In okitsu-wase frees, water potential of leaf was decreased rapidly in root confinement frees. In the confinement trees, hydraulic conductivity transpiration rate and TTC reducing activity were decreased, and the ratio of cortex of fine root was high. These results indicate that the dwarfing and improvement of fruit quality by root confinement may be due to histological and physiological changes of root. Eighteen months after grafting, the dry matter of top was the greatest on vigorous rootstock. Endogenous IAA and ABA were measured in the new shoots and fibrous roots. The IAA level in shoots was highest in vigorous rootstock, and ABA level was highest in dwarf rootstock. The levels in roots ware not clear. The vigorous rootstok had the highest Th and IAA/ABA ratios in the new shoot.