Physiological Mechanism Of Soil Compaction On Transportation And Distribution Of Photosynthate In Sweet Potato

In order to research the physiological mechanism of soil compaction on transportation and distribution of photosynthate in sweet potato, we used two typical varieties of sweet potato,including Beijing 553 and Long 9. The treatments included loose soil treatment, control treatment and hard soil treatment. The study was carried out in Agronomy Experimental Station of Shandong Agriculture University. The main results were as follows: 1. Yield and its composing factors of sweet potatoCompared with control treatment, biomass and storage root lumps per plant of loose soil treatment had no difference, but fresh weight lump and harvest index of control treatment was significantly higher. Root tuber yield of control treatment increased by over 19%. Biomass, storage root lumps per plant, fresh weight lump and harvest index of hard soil treatment was significantly lower. Root tuber yield of hard soil treatment decreased by over 30%. 2. Dry matter accumulation and distributionAs soil compaction decreased,Dry matter accumulation was significantly higher,dry matter of over ground part increased rapidly in the early stage while declined slightly; the initial potential, the dry matter production potential, the mean dry matter accumulation rate and the max dry matter accumulation rate of storage root improved significantly;the time of the max dry matter accumulation rate was early; contribution rate to root tuber yield formation in early root tuber bulking stage improved significantly; photosynthate accumulate in storage root was faster. Loose soil treatment could significantly improve the photosynthate distribution rate of root tuber and rate of T/R, effectively prevent the excessive aboveground growth, and increase the harvest index. The higher soil temperature diurnal range of loose soil treatment maybe was the reason why loose soil was conducive to early-formation and early-development of root tubers. 3. Key effect of soil compaction on transportation and distribution of photosynthateLoose soil could extend the functional period of leaf, increase leaf area, and improve photosynthetic rate, stomata conductance, intercellular CO2 concentration and transpiration rate of functional leaves, and improve the deliverability of photosynthate in functional leaves. Compared with control treatment,loose soil treatment could improve SPS activity of functional leaves and reduce sugar and soluble sugar content of leaves, so the ability of photosynthate loading in functional leaves was improved significantly.As soil compaction decreased, sugar and soluble sugar content of petiole increased significantly, and sugar and soluble sugar content of stem declined significantly; sugar and soluble sugar content of top part of stem increased significantly, while sugar and soluble sugar content of middle and basal part of stem significantly declined. So the loose soil was conducive to photosynthate loading and unloading at the same time. Meanwhile, loose soil reduced the residence of carbohydrate of stem, so the effect of loose soil on photosynthate unloading was more significant that of loose on photosynthate loading.Loose soil could increase ATP and starch content of storage root significantly,and improve ATPase, SS and ADPGPPase activity of storage root significantly. So the loose soil was significantly conducive to photosynthate unloading. In conclusion, the loose soil was conducive to photosynthate loading and unloading at the same time, however, considering that stranded carbohydrate of middle and basal part of stem declined significantly, the effect of loose soil on photosynthate unloading was more significant that of loose on photosynthate loading.