Single nodal cuttings at the 1st, 3rd and 5th positions from the shoot apex of in vitrocultured coffee (Coffea arabusta) plants were grown on half strength MS agar medium under photoautotrophic conditions. Three photoperiod/dark period temperatures were selected as follows: 28/22°C, 26/26°C and 22/16°C. The culture was exposed to a CO2concentration of 400-450 μmol mol-1and PPF of 120 μmol m-2s-1under a 16h photoperiod. The growth parameters of the coffee plants cultured in vitro from each nodal cutting were determined after 45 days. Under the 22/16°C regime coffee plant growth was obviously retarded, regardless of the position of the nodal cuttings. There were differences in growth between the 26/26°C and 28/22°C regimes, with the same daily average temperature. The increase in the fresh weight and leaf area of the shoots under the 28/22°C regime was significantly larger than that under the 26/26°C regime when the nodal cutting positions were compared. The shoot elongation was significantly greater under the 28/22°C regime for all the treatments. There was a gradual reduction in the leaf area depending on the position of the nodal cuttings from the apex. The value of the relative growth rate of the coffee plants cultured in vitrofrom the third nodal cutting under the 26/26°C regime was the highest on day 45. However, the value of the net photosynthetic rate of the plants cultured in vitro, Pn, was the highest under the 28/22°C regime for the 1st nodal cutting position and the lowest under the 22/16°C regime for the 5th nodal cutting position, when measured on day 20. Pnvalue of the plants grown under the 26/26°C regime was lower than that under the 28/22°C regime on both days 20 and 32.
The conditions for surface runoff generation, which is usually strongly related to the process of soil erosion, were analyzed in three plots at different cultivated sloping sites in North and Northeast Thailand using a runoff gauge connected to a data-logger. In most of the cases, the rainfall intensity and the surface soil moisture contributed significantly to surface runoff generation. The rainfall intensity in the Khon Kaen plot on sandy soils was higher than that in the other two plots with finetextured soils in the northern region, and surface runoff occasionally occurred throughout the rainy season with no clear seasonal trend, unlike in the other two plots, where surface runoff occurred more often during the latter half of the rainy season due to the higher rainfall intensity and/or capillary saturation of surface soils. The proportion of the surface runoff generated in relation to the amount of rainfall increased with the increase of the slope gradient of the plots. The proportion of the amount of soil erosion in relation to amount of surface runoff was, however, the largest in the sandy plot of Khon Kaen with the lowest slope gradient, indicating that the sandy soils were more easily eroded than the clayey soils presumably due to the weakly organized structure of the soil aggregates. Therefore, the conditions that enhance the risk of surface runoff and soil erosion were found to vary and should be taken into account for agricultural management in the respective regions.
An analysis was performed on chili pepper [Capsicum annuum (L.) cv. Huay Si Thon and Shishito] seed vigor and quality produced by plants grown under control and high temperature conditions (29±2/24±2 and 36± 2/27±2°C, mean day and night temperatures, respectively) after anthesis to elucidate the effect of high temperature during seed development on seed quality. High temperature significantly reduced fruit growth in both varieties. More than 20 % of the seeds produced under the high temperature regime were flat with a dark brown color and did not germinate. High temperature inhibited seed fresh and dry weight increase and the seed size was slightly reduced. Standard germination of Huay Si Thon and Shishito seeds occurring under the high temperature conditions was lower than that of the control seeds by 28 and 25 %, respectively. Similarly, seed vigor was reduced, as evidenced by the reduction in the accelerated aging germination rate and the higher value of the germination index. Protein content was maximal during the early stages of seed development and decreased afterwards continuously during the seed maturation stage, while no conspicuous reduction of the protein content by heat was observed. High temperature reduced the carbohydrate content of seeds by 40 % in Huay Si Ton and 50 % in Shishito, respectively. High temperature reduced the lipid content to less than half. These results suggested that high temperature during seed development reduced chili pepper seed germination and vigor, presumably due to the limitation in the accumulation of storage products, especially carbohydrates, and lipids.