磷素对甘薯生长前期源库关系建立和平衡的影响

通过2年盆栽试验研究不施磷P₀（P₂O₅ 0 g/kg）、适量施磷P_0.04（P₂O₅ 0.04 g/kg）和过量施磷P_0.08（P₂O₅ 0.08 g/kg）对鲜食型甘薯‘烟薯25’和‘普薯32’生长前期（栽后0~40 d）根系活力、根系形态分化、潜在块根重量、结薯数、薯块重量、根生物量、叶面积、茎叶生物量、根干物质分配比例、茎叶干物质分配比例及根冠比的影响。结果表明,在块根形成期（栽后0~30 d）,与不施磷处理相比,适量施磷显著提高了甘薯总根条数、根尖数、总根长、根系表面积、根系平均直径、根系体积和总根鲜重,并显著提高了根系活力,提高了潜在块根鲜重;显著提高叶面积、叶鲜重、茎鲜重、地上部总鲜重;显著提高甘薯茎叶干重、根干重和植株干重,显著增加干物质根分配比例,降低干物质茎叶分配比,显著提高根冠比,为块根形成提供良好的物质基础。而过量施磷抑制干物质在根中的分配比例,导致根冠比降低,不利于块根的形成。在封垄期（栽后40 d）,与不施磷处理相比,适量施磷可以显著增加单株结薯数（主要提高直径5 mm以上的块根数量）、单薯重和单株薯重,若继续增加施磷量将导致单株结薯数和单薯重显著降低。因此,适量施磷可以促进甘薯根系和茎叶发育,增加干物质根分配比例,降低干物质茎叶分配比,显著提高根冠比,增加甘薯单株结薯数和单薯重,提高单株薯重,促进甘薯生长前期源库关系建立和平衡,为甘薯丰产奠定基础。

Effects of Phosphorus Application on the Establishment of Source-sink Balance at the Initial Stage of Sweetpotato Root Development

A two-year pot-sand-culture experiment was conducted to investigate the root activity, root morphology, fresh weight and diameter of potential storage root, storage root numbers, single storage root fresh weight, root biomass, leaves area, stem-leaves biomass and both root and top dry matter allocation rate as well as root-top ratio (R/T) under phosphorus application P_0.04 (P₂O₅ 0.04 g/kg) on two sweetpotato varieties ‘Yanshu 25’ and ‘Pushu 32’. Compared with P₀ (P₂O₅ 0 g/kg), the total roots number, total roots fresh weight, length, surface area, mean diameter, volum and tips as well as root activity and the fresh weight and diameter of potential storage root at the early growth stage (0-30 days after planting) were significantly increased under proper phosphorus application (P_0.04). Further more, sweetpotato leaf area index, fresh leaf weight, fresh stem weight, above-part fresh weight and dry weight accumulation of root, above-part and whole plant as well as dry matter to root partition ratio and root-top ratio were also increased at significant level under proper phosphorus application (P_0.04). However, excessive P_0.08 (P₂O₅ 0.08 g/kg) inhibited the distribution of dry matter in roots, resulting in the decrease of root-top ratio, which was not conducive to the formation of storage root. At closure stage (40 days after planting), compared with P₀, appropriate amount of phosphorus P_0.04 (P₂O₅ 0.04 g/kg) significantly increased the number of single plant storage root number (the number of storage root with diameter more than 5 mm was increased) and single storage root fresh weight, thus increased the weight of single plant. If the amount of phosphorus continued to increase, the number storage root number and single storage root fresh weight decreased significantly. Appropriate phosphorus application is of great significance to sweetpotato storage root formation. It would be beneficial to the formation of adventitious root, the growth and development of stem and leaf, and the dry matter synthesis of stem and leaf, thus laying a good material foundation for the formation of storage root, it could promote the distribution of dry matter to the root, increase the ratio of root to top, and promote the harmonious growth of plant, beneficial to storage root formation and the increase of storage root number.