1985 Volume 31 Issue 2 Pages 159-166
In order to evaluate the drought resistance of warm season forage species, Paspalum dilatatum cv. Kyushu 5 (dallisgrass), Chloris gayana cv. Katambora (rhodesgrass), Sorghum birolor cv. Sweet siox IV (sweet sorghum), Zea mays cv. Snowdent 1 (corn), Coix lacryma Jobi (job's tears) were grown on the pots, of which soil moisture was adjusted to pF 1.7-2.0, pF 2.3-2.5, pF 2.8-3.0 and their photosynthetic rates, leaf water potentials, leaf resistances were examined. And, rhodesgrass being the most tolerant, sweet sorghum and job's tears being sensitive species to water stress, were grown at the graded level of soil moisture, and the distribution of ^<14>C assimilated among their various organs and organic constituents were determined. The results obtained are summarized as follows ; 1) The apparent photosynthetic rates of species decreased by water stress, and especially, these decreases were remarkable in the sensitive species. 2) The disadvantage of root development of the sensitive species by water stress was particularly due to the lowering of translocation of assimilated carbohydrate from leaves to roots. 3) Under the water stress condition, species had enhanced incorporation of assimilated ^<14>C into low molecular constitutes such as amino acids, and soluble sugar fractions, but not much into high molecular constitutes such as starch, protein and lignin-cellulose fractions. 4) ^<14>C incorporation into lignin-cellulose and protein fractions of job's tears root was apparently suppresed by water stress, but that of rhodes-grass was not much as job's tears. It is concluded from these results that drought resistant species might maintain their dry matter production ability greater through maintaining higher photosynthetic rate, and also their root development well by the efficient distribution of assimilates into roots or high molecular root constitutes such as lignin-cellulose.
