The Productivity of Cassava (Manihot esculenta Crantz) in Kagoshima, Japan, Which Belongs to the Temperate Zone

The cultivation period of cassava in Kagoshima, Japan, which belongs to the temperate zone, is limited by the low temperature in winter. To maximize productivity under this limited period, investigations were conducted on the gas exchange rate and production structure relating to light utilization in a plant community of cassava grown under different nitrogen fertilization conditions. Fertilization either at planting or three months after planting significantly increased stomatal conductance in the upper canopy and root dry weight compared to the control. In addition, the dry matter distribution to stem and root dry matter rate of initial fertilization treatment were significantly higher, and the dry matter distribution to root of the latter fertilization treatment tended to be higher than that of the control. However, light transmittance at 80 cm below the top of the canopy was almost the same as that at the ground surface, which was a common tendency among the treatments. In conclusion, it was revealed that the effects of fertilization on yield were mainly the increase in the gas exchange rate of individual leaves and the change of dry matter distribution rather than an improvement in light transmittance.

Physiological and biomass partitioning shifts to water stress under distinct soil types in Populus deltoides saplings

Aims Although soil environments exist extensive heterogeneity for many plants with a wide range of distribution, researches about effects of soil conditions on plants’ tolerance and adaptation are particularly inadequate. In our study, the aims are to reveal physiological strategies of Populus deltoides against drought stress under different soil conditions and to select the most suitable soil type for P. deltoides plantation. Methods Under controlled conditions, we used P. deltoides as a model species to detect differences in gas exchange rate, antioxidative capacity, nitrogen metabolism and biomass accumulation and partitioning in response to drought stress under three mineral soil types with distinct physicochemical characters, i.e. red soil (RS), yellow soil (YS) and yellow-brown soil (BS). Important Findings Exposure to 25% of field water holding capacity in soil for 3 months had significantly decreased biomass of all organs, photosynthetic rate, enzyme activities related to N assimilation, but increased H2O2, malondialdehyde and content of both NO3− and NH4+, when P. deltoides was planted in both RS and YS. In contrast, under BS, there are slightly negative effects exerted by water deficit on total biomass, gas exchange rate, activities of enzymes related to nitrogen metabolism and membrane damage caused by reactive oxygen species, which can be associated with a consistent increase in superoxide dismutase, peroxidase and catalase, and a higher ratio of root mass to shoot mass. It is concluded that, such higher capacity in tolerance and adaptation against drought stress under BS relative to both RS and YS could be accounted for more sufficient nutrient provision in soil parental materials and better soil aeration conditions which play a vital role in plant acclimation to water shortage. Our study also revealed that, distribution areas of BS might be preferable for cultivation of P. deltoides, when compared with those of RS and YS.