Off-season floral induction in ‘Cat Hoa Loc’ mango by using paclobutrazol, potassium nitrate and “Chemical Compound Inducing Flowering”, a chemical product developed at Can Tho University (abbr. CTU) consisting of potassium nitrate, phosphoric acid and minor elements was carried out in Cao Lanh district, Dong Thap province, Viet Nam from May 1996 to May 1997. Paclobutrazol was applied at the rate of 5g per tree by collar drenching, while KNO₃ and CTU were used at a concentration of 15g/1 and applied twice as a foliar spray.
The results showed that the floral induction chemicals were able to induce flowering in ‘Cat Hoa Loc’mango in September except for the treatment of 6-year-old trees with KNO₃. Off-season flowering was extended until the end of December. Paclobutrazol was the most effective chemical compared with both KNO₃ and CTU. It induced flowering at 85 days after the treatment 4.3 times in about 15.6% of the total number of shoots per tree compared to less than 3 times and less than 6% of the total number of shoots per tree in the case of other chemicals and control treatments. Flowering of the control occurred in November.
Off-season harvest extended from December 1996 to March 1997. The fruits in which flowering was induced by paclobutrazol were harvested in early of December, 85 days after flowering (4 harvests) . The highest off season yield (35.3kg/tree) was obtained with the paclobutrazol treatment in 8-year-old trees. However, the chemical treatments did not promote flowering in 6 and 7-year-old trees.

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A multiple regression model was developed using statistical records for longan production and meteorological records in order to identify the factors that caused variations in longan yield in northern Thailand. Longan yield varied from year to year in both Lamphun and Chiang Mai provinces. Stepwise regression (forward selection) was used to find a good subset of variables for estimating longan yield. The variables generating the best fits were chilling degree-days, previous year's yield, and daily minimum temperatures in February and March in Lamphun province, while production year and previous year's yield in Chiang Mai province. For calculating chilling degree-days, 15°C was used as a base temperature because the multiple correlation coefficient was highest at 15°C. Standardized partial regression coefficients indicated that chilling degree-days in Lamphun province and yield trend with time in Chiang Mai province were more important factors in determining longan yield than the previous year's yield.

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Questionnaires were distributed to longan farmers in the Sarapee and Ban Aie districts of Chiang Mai province to identify the problems confronting longan growers in northern Thailand. The mean temperatures in December were lower in Ban Aie than in Sarapee. Longan growers considered that insect and mite pests caused the most serious damage to longan production in both areas. Judging from the response of the growers to the questionnaires, however, it appeared that insect and mite pests could be controlled when insecticides were sprayed two times per year in Sarapee and five times per year in Ban Aie. Longan growers in Sarapee considered that poor flowering was the next most serious problem after insect pest infestation, while growers in Ban Aie indicated fruit set instead. Longan growers who was confronted with poor flowering of longan, applied large amounts of nitrogen and carried out heavier pruning. These results indicate that poor flowering may be more serious in the southern districts than in the northern districts of Chiang Mai province.

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Growth of pollen tube in the pistil of white sapote‘Florida’flowers was observed using a fluorescence microscope. The number of hours required for a pollen tube to penetrate an ovule was investigated at 10, 15, 20, 25, and 30°C. Pollen tube penetrated an ovule within 8 hours at 30°C and the penetration took a longer time at lower temperatures. The effective pollination period (EPP) in white sapote was estimated from the results of fruit set brought about by hand pollination at different times after anthesis. The EPP was 15 days on flowers in March and the period was shorter in April when temperatures increased. Observations of the changes in the stigma coloration showed that the EPP appeared to continue until the stigma became brown.

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The time-course changes in respiration and ethylene production were investigated in‘Yellow’white sapote fruits stored at 1, 5, 10, 15, 20, 25, 30 and 35 °C. Increase in the respiration rate coincided with that of ethylene production at 30 and 35 °C. However, the ethylene production rate increased after the increase in the respiration rate at 5-25 °C. Within 5 to 25 °C ranges, the respiration rate and ethylene production rate at the respective peaks were higher and the ethylene production peak occurred earlier than the respiration peak at higher temperatures. No ethylene production and a low respiration rate were induced during storage at 1 °C.
The fruits became soft and edible at the time of peak ethylene production. The storage temperature did not affect the content of total soluble solids of the ripened fruits. Browning of the fruit skin was observed at 5 °C and above 30 °C, while browning did not occur under relatively warm conditions temperature ranging from 10 to 25 °C. At 5 °C, softening occurred only on the fruit surface, and the surface became water-soaked. All the fruits stored at 1 °C for 10, 20, 46 and 63 days could ripen after they were transferred to an environment at 25 °C. Since chilling injury occurred in the fruits stored for 63 days, it is suggested that the storage period could be extended to 46 days by storage at 1°C.

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The changes in the chemical composition and in vitro ruminal digestibility of components of different growth stages of saltwort (Salicornia herbaceaL.), a kind of halophyte growing in Japan, were analyzed and the yield of digestible components of the plants was estimated. Saltwort plants were cultivated (day of seeding is Day 0) in plastic cases and harvested at 3 vegetative stages (early, middle and late stages: Day 49, 79 and 110, respectively) and two reproductive stages (flowering and post- flowering stages; Day 131 and 160, respectively) . Saltwort contained high levels of crude ash (CA; 32.1-36.0 % DM) and sodium chloride (19.1-26.9 % DM), relatively high levels of crude protein (CP; 13.1-22.4 % DM) and a low level of neutral detergent fiber (NDF) . The contents of NDF, acid detergent fiber (ADF) and organic cell wall (OCW) of the plants increased with the progression of the growth stages (p<0.01 for each nutrient), while the contents of CP and digestible NDF (DNDF) decreased (p<0.01 and p<0.05, respectively) . Although the degradability of saltwort plants at 0 and 72 hr of incubation decreased with the progression of growth (p<0.01 at each time), the digestibility (difference between the degradablty at 0 and 72 hr) of the halophyte at each growth stage was relatively constant. The estimated yield of the maximum degradable OM (with 72 hr of incubation), digestible OM and DNDF of saltwort increased logarithmically with the progression of the growth stages (p<0.001 for each nutrient), and the yield of these nutrients increased remarkably at the later growth stage of the plants. These results indicate that the optimal harvesting period of saltwort for use as feed for ruminants should coincide with the post-flowering stage when the seeds are premature.

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Elephant foot yams are grown as ground-layer crops in home gardens because they are tolerant to low light intensities and low fertility. However, the cultural practices and use of elephant foot yams have not been studied. Therefore, field surveys and interviews of farmers were carried out in West, Central and East Java, and Yogjakarta. The number of home gardens in which elephant foot yams were cultivated was larger in Central Java than in West Java. Farmers use corms and leaves as staple crops and vegetables, respectively, as well as for feedstuffs. Some farmers harvest corms only when rice production is low. Although elephant foot yams play a minor role as food crops, they have a potential as industrial crop because they can be cultivated under the canopy of plantation crops.

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Groundwater pollution by nitrogen is a common environmental problem to the Southwest Islands of Japan where the geological substratum is covered with coral limestone under the subtropical climate conditions. Nitrogen loading factor, the ratio of nitrogen derived from each source and loaded into groundwater, is one of the most important factors in the analysis of nitrogen pollution. In order to estimate this factor, the nitrogen concentrations of groundwater in some sections of Okinoerabu Island were determined. The amounts of nitrogen derived from each source in the same sections of the island were calculated. The loading factor of nitrogen from each source into the groundwater was estimated by multiple regression analysis of the nitrogen concentration and the nitrogen loads in each section. The influence of the cultivation of various crops, livestock breeding and domestic wastes on the quality of groundwater was analyzed as follows:
1. The loading factors of nitrogen from the fertilizers applied for cut flower cultivation, fertilizers applied for other crops, livestock wastes and domestic wastes were estimated to be 71, 21, 24 and 110%, respectively by multiple regression analysis, R²= 0.979 (n =11) .
2. The proportion of nitrogen from all the fertilizers to the total amount of nitrogen loaded into the groundwater in each section ranged from 44 to 68%.
3. The amount of nitrogen loaded from each unit area of farm was 480 kg⋅ha^-1for cut flower cultivation and 40 kg⋅ha^-1for the cultivation of other crops. The amount of the former was more than ten times greater than that of the latter.
4. Study of land use in the area around the wells for municipal water supply in Wadomari-town showed that 6.6 ha of the farms in this area were converted into the farms for cut flower cultivation. The amount of nitrogen loaded from the flower farms increased the nitrogen concentration in the groundwater in this area by 1.8mg⋅L^-1.

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In a previous paper, we outlined how jasmonic acid (JA) and gibberellin-like substances participate in the initiation of tuber enlargement in water yams (Dioscoyea alata L.) . In this study, we examined the relationship between the initiation of tuber enlargement and the changes in the content of endogenous JA in water yams subjected to short day treatment and exposes to natural day length.
Synthesis of JA was activated by short day length. The time when the JA content became maximum varied in each strain and occurred earlier in the extremely early maturing strains than in the late maturing strains. In each strain, the peak of the JA content coincided with the initiation of tuber enlargement. However, the JA content decreased significantly after the initiation of tuber enlargement in each strain, even though vigorous growth and enlargement of the tuber continued thereafter.
The results of this study indicate that JA may be related to the initiation of tuber enlargement in water yam.
The JA content of the late maturing strains exceeded that of the extremely early maturing strains, suggesting that the sensitivity to JA varies with the earliness of each strain.

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