介绍了限根栽培措施和理论依据(地上地下的相关性、根系局部营养、生长冗余)、限根对植物生长发育的影响、限根的生理反应和作用机制以及限根技术的应用等间题。

Recently, research on Ca2+ transport in plants has been focused on cellular andmolecular level. But the uptake, transport and distribution are also very important for calcium to accomplish its function at whole plant level. There are many cells along the way of transport of Ca2+ from root to shoot, and Ca2+ passes either through the cytoplasm of cells linked by plasmodesmata (the symplast) or through the spaces between cells (the apoplast), which include Ca2+ uptake by root cells, Ca2+ transport from root cortex to and through the xylem, and then out of it into leaves or fruits. Ca2+ channels, Ca2+/H+ antiporter and Ca2+-ATPase play roles in the uptake and transport of Ca2+ in root cells. To be transported fromroot surface to xylem, Ca2+ needs to traverse endodermal cells and xylem parenchyma cells. Endodermal Casparian band, the main barrier for the apoplastic movement of ions into the stele, compels some Ca2+ to enter root symplast through Ca2+ channels in endodermal cells and then reach xylem parenchyma. Ca2+-ATPasemay drive Ca2+ into the stelar apoplast from xylem parenchyma. Some Ca2+ effuses from endodermal cell and then get to xylem through apoplastic pathway. Ca2+ is transported in plant xylem vessel in chelate form and the speed of water flow is the key factor Ca2+ transport via xylem in trunk. There are both apoplastic and symplastic pathways of Ca2+ transport in fruit or leaf tissue too.

The early-response of roots to water loss and the signal transduction of water loss to abscisic acid (ABA) biosynthesis were studied by polyethylene glycol (PEG 6000) treatments to apple rootstock (Malus hupenensis Reld) seedlings. The results show that the ABA content, the H2O2 production rate, the lipoxygenase (LOX) activity and the protein kinase (PK) activity all increase during water loss (30% PEG treatment) in apple roots. H2O2 content reaches a peak at 30～40 min, then drops and rises again at 180 min following treatment. Increase of H2O2 is the earliest and of ABA content is the latest among these events. The absorbance of H2O2 and inhibition of LOX reduce the ABA accumulation during water loss. Both exogenous H2O2 and soybean LOX are able to increase ABA content. The Ca2+ chelater (EGTA) and the inhibitor of PK and LOX all reduce the increment of ABA after water loss. The activity of LOX and PK increases after treatment by 1 mmol/L H2O2 in intact roots and a PK inhibitor reduces the increase of LOX activity by PEG and H2O2. The PEG treatment-induced increases of H2O2 content, PK and LOX activity all decrease after EGTA pretreatment. It suggests that the Ca2+, protein phosphorylation, active oxygen species and LOX are all involved in the ABA biosynthesis induced by water loss; the change of cytosol Ca2+ and H2O2 is the earliest event and LOX may be a key enzyme in some conditions. The pathway of the signaling cascade associated with water loss and ABA may be: PEG treatment → loss of cell water → loss of cell turgor → mechanical process → Ca2+ → H2O2 → PK → LOX → ABA accumulation.

The effect of plant growth substance and fertilizer on root formation was studied in new planted apple tree (Malus pumila Mill / Malus hupenensis Rhed). The results indicated that urea and IBA (Indolebutyric acid) and sheep dung all increased the total number and activity of new roots and changed the ratio of absorbing root to extensive root obviously. Urea increased the number of extensive root and decreased the ratio of root to shoot mostly. IBA lengthened the extensive root and increased the ratio of root to shoot obviously. Sheep dung increased the number of absorbing root and increased the ratio of absorbing root to extensive root, divided new root into mangy branches, increased the fresh weight of root and thicken extensive root. The fresh weight of root increased and the ratio of root to shoot declined after urea added to sheep dung. Both the ratio of absorbing root to extensive root and root fresh weight was increased after IBA added to sheep dung, then the ratio of root to shoot had no change obviously.

The uptake rate of Ca2+ and Ca2+-ATPase ultracytochemical localization were studied using Malus hupenensis Rehd seedlings and pot-cultured two-year-old apple trees (‘Starkrimson’/Malus hupenensis Rehd), after treatment with IBA. The results showed, IBA increased activity of roots and Ca2+-ATPase and rate of Ca2+ uptake. But Ca2+ uptake rates were inhibited by 2,4-DNP, the metabolic inhibitor, and the inhibition degree was higher under low Ca2+ concentrations (0 ～0.5 mmol/L) than high Ca2+ concentrations (0.5～5 mmol/L). The Km and Imax and the ratio (Imax/Km) all increased, and the inhibition degrees were higher in excised root than intact roots after roots were treated with IBA. The Imax and a (Imax/Km) increased but the Km after spraying IBA on leaves. 2,4-DNP inhibited the effects of IBA on Ca2+ absorption. Ca2+-ATPase was located on the cytoplasmic membrane and the vacuolar membrane. The activity of Ca2+-ATPase on the cytoplasmic membrane was increased significantly after treating by IBA.