Abstract
The present study was made to clarify the relationship between the physical composition of a sand media and the growth response of cucumber seedlings under various temperatures. The night- and day-temperatures were set in combinations of 20°, 25°and 30°C.
1. Dry top weight between cucumber seedlings grown on two particle sizes of sand-very coarse sand media (particle size ca. 2-1mm) and fine sand media (ca. 0.2-0.02mm)-did not show any definite difference in the case of either a night-or day-temperature of 20°C. Such a difference was most notable at 30°C, in both night- and day-temperatures, dry top weight of the very coarse sand medium being only 60% of that of the fine sand medium. Leaf dry weight/leaf area was 2.07 mg/cm2 at 30°C in thevery coarse sand medium. In the fine sand medium at 20° or 30°C and the very coarse sand medium at 20°C, it was ca. 1.7mg/cm2.
2. The effect of irrigation frequency on the growth rate of cucumber seedlings was represented by dry top weight percentage, taking that in the very coarse sand medium with one irrigation a day as 100%. In the very coarse sand medium, the dry top weight did not increase until receiving 6 irrigations per day. By 13 irrigations, however, the dry top weight was 160%, and by 49 irrigations, 240%. These values showed a similar tendency in the fine sand medium with once a day irrigation. In the fine sand medium, on the other hand, the dry top weight decreased with frequency of irrigation. The value was 275% with one irrigation and 150% with 6 irrigations. Furthermore, leaf dry weight/leaf area which was definitely affected by irrigation showed 2.05mg/cm2 in the very coarse sand medium with once a day irrigation. This was quite thick as compared with 1.5 to 1.7mg/cm2 in the other media; and these thicker leaves showed rather prominent xeromorphism.
