Seasonality of cropping in village homegardens was surveyed at Don Daeng, Northeastern Thailand, from July, 1983 to February, 1984. Chilli was the dominant crop, accounting for 40% of the garden land area in all seasons, though 156 useful plants were recognized there. The planting frequency of papaya, maize, yard long bean, greater yam declined from the rainy season to dry season. Cultivation of garlic, shallot and Brassica spp. predominated in the dry season. Crop yield was the highest in November and the lowest in August. Cultivation activity changed appreciably each month. This seasonality pattern was presumably related to the ecological traits of the crops, climatic conditions and rice cropping calendar. Removal of competition with rice cultivation may promote crop production in garden land and bring stability to rain-fed agriculture.

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The effects of pruning and harvesting treatments on the growth, leaf-yield and leaf-quality of three-year-old Plau-Noi trees were investigated.
The suitable pruning and harvesting systems in order to obtain a high leaf-yield and high plaunotol content in the leaves, as well as to keep a tree vigorous and healthy were as follows:
1. A suitable pruning system during the growth-resting period: The tall trees should be top-cut at about 2m above the ground. The stems with few branches should be thinned out and the branches with few buds should be cut back. Pruning to maintain health also included the removal of all crossing, immature, thin and weak shoots which frequently develop in the center of unpruned trees.
2. A suitable harvesting system during the growing period: Only the top part of branches with many leaves should be lightly cut back. We had better to avoid a heavy pruning in order to increase the leaf-yield and plaunotol content in the leaves in the next harvesting.
In conclusion, based on both methods of pruning and harvesting, it is possible for us to harvest the leaves of more than three-year-old Plau-Noi trees in the following time. (a) Early stage of growing period: 1st harvesting time; late May or late June. 2nd harvesting time; late July or late August. (b) Late stage of growing period: 3rd harvesting time; late October or late November.

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From Hokkaido to Okinawa Prefecture, 52 clones of Imperata cylindrica were collected and the data of sprouting of new shoots, heading and death of aerial parts were recorded. A total of 260 ramets (5 ramets×52 clones) were planted in clay pots (20 cm diameter, 19 cm depth) individually and plant height, number of shoots, number of rhizomes and dry weight of each organ were determined.
Principal component analysis based on the correlation matrix of the ten characters was applied using 47 clones except for five clones from Hokkaido, Akita, Amami and Ryukyu Islands for which the phenological characters could not be assessed.
The accumulated contribution from the first to the third components reached 84.4%. The first principal component (Z₁), the second (Z₂) and the third (Z₃) refer to plant height and phenology, rhizome length and number, and dry matter partitioning ratio to rhizomes, respectively.
The 47 clones were divided into three groups corresponding to the adaptive characteristics to their original habitats. Group A consisted of clones of I. cylindrica var. genuina from the northern part of the Tohoku district, which exhibited a low value for plant height and emerged late in spring. Group B which contained clones of var. koenigii from the southern part of the Tohoku to northern part of the Kyushu districts showed characteristics intermediate between those of groups A and C. Group C consisted of clones of var. koenigii from the southern part of the Kyushu district with a high value for plant height and in which the aerial parts died in late winter.

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Seasonality of chilli production in village home gardens was surveyed in Don Daeng village, in Northeast Thailand. The average weight of fresh fruit harvested was 3 kg/100 m²/month or 2 kg/100 plants! month, and the yield in September and October was higher than that in other months for the period of the survey from July 1983 to February 1984. Fruit yield/100m² was controlled definitely by the fruit yield/plant, and not by the number of plants/m². Production in July and August was restricted by the inhibition of flowering by rain, and labour competition with rice cultivation. Lower production after November was caused by the renewal of chilli plants.

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The current study was undertaken to determine the effects of the plant growth retardant; cyclohexandion (KUH833, Kumiai Chemical Co.) on the growth and ripening of sugarcane, as compared with the effects of the known plant growth regulator glyphosate. The study was carried out under high temperature and moist drip irrigation conditions in a greenhouse at the Tokyo University of Agriculture during the period July through September 1988. Forty sugarcane plants (variety NCO 310, grown in 1/2000a pots) were subjected to the treatment at the 21st leaf stage. Aqueous solutions of glyphosate at two concentrations were applied to four young leaves, No. 2 through No. 5 (the spindle leaf being designated as No. 1) . The treatment consisted of brushing the leaves of the test plants with 2 ml of a solution containing 2 mg of KUH833, 5mg of KUH833, or 4 mg of glyphosate. The growth of the apical and intercalary meristem of the stalk as well as the young leaf tissues of the upper leaf blades was markedly inhibited by KUH833 at both concentrations and by the glyphosate solution. Furthermore, no reduction of the chlorophyll content was detected by the treatment with these chimicals. Six weeks after the treatment, the average Brix percentage of the treated plants was 14.04% and 14.22% after the application of 2 mg and 5mg KUH833, respectively. The Brix percentage was 19.09% after the application of a 4 mg solution of glyphosate, and 11.0% in the control. Thus the application of both substances resulted in considerable increases in the Brix percentage compared with the untreated control plants. The growth inhibitory effects of KUH833 lasted only 2 to 3 weeks, in comparison with 6 weeks for the glyphosate treatment, thus resulting in a lower Brix percentage for the KUH833-treated plants. It was therefore concluded that the optimum concentration of KUH833 for the inhibition of growth in the sugarcane plant was higher than the maximum 5mg used in the present study.

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Internodal elongation and endogenous ethylene concentration were analysed in floating or deep water rice stem sections submerged at different water depths. The elongation rate of the internodes was independent of the water depth. Elongation rate and ethylene concentration of the internodes were high in the stem sections submerged completely in water, but they decreased when parts of the stem sections were above the water surface. In the stem sections previously submerged, in which the ethylene levels were high, internodal elongation continued after parts of the sections were exposed to ambient air even though the ethylene levels decreased. These results suggest that internodal elongation is independent of the water pressure and that the different concentrations of internodal ethylene partially reflect the difference in the diffusion rate of ethylene in water. They also suggest that ethylene acts as a trigger of internodal elongation.

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The effects of several plant hormones on the internodal elongation of stem sections and endogenous levels of gibberellin in submerged and ethylene-treated stem sections were investigated in floating rice (Oryza sativa L. cv Habiganj Aman II) . Gibberellic acid (GA₃) and ethylene induced internodal elongation of stem sections. Abscisic acid (ABA) and benzyl adenine (BA) at any concentration (≤ 1 mM) did not promote the internodal elongation of the sections regardless of the presence of GA₃. However, indoleacetic acid (IAA) (0.1 to 10 μM) promoted the internodal elongation induced by GA₃. Submergence increased the endogenous level of gibberellin in the stem sections unlike ethylene. It is suggested that gibberellin and ethylene as well as IAA may be involved in the internodal elongation of floating rice. Also, both gibberellin and ethylene may be involved in different processes of internodal elongation of floating rice under submergence.

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A few experiments were carried out to analyze the mechanism underlying the inhibition of tiller buds by submergence in deep water of the subtending leaf sheaths in floating rice. The growth of the tiller buds was inhibited by the deep water treatments. Air was supplied, under deep water, to the inner space between the leaf sheaths where the young 4th node or 5th node tiller bud grows (while inhibited by deep water) at the plant age of 5 or 6, respectively. The aeration treatment promoted the growth of the exposed tiller bud and of that immediately below it. A small window was made in the midrib of the basal part of the 5th leaf sheath in order to expose the subtended 5th node tiller bud to water and drown it under shallow water (deep enough to drown the tiller bud) conditions at the plant age of 6. The drowning treatment inhibited the growth of the exposed tiller bud to a similar extent to that of the deep water treatment, in spite of the shallow water conditions. Aeration applied to the tiller bud inhibited by the drowning treatment promoted the growth. On the basis of the results obtained it is suggested that gas exchange between the inner space and atmosphere may be inhibited by the submergence of the tips of leaf sheaths, and that the lack of oxygen required for respiration or accumulation of ethylene may be the cause of the inhibition of growth of the tiller buds. In future further studies will be carried out to analyze the role of ethylene in this function.

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In Plau-Noi plantations where root rot disease could not be eradicated, Plau-Yai, a closely related species of Plau-Noi, showed a high resistance to the disease.
We succeeded in grafting Plau-Noi, Croton sublyratus KURZ trees used as scion onto the rootstock of Plau-Yai, C. oblongifolius ROXB trees.
The characteristics of the Plau-Noi trees with Plau-Yai roots were as follows:
1. The stock of Plau-Yai did not affect the content of plaunotol in the leaves of the grafted Plau-Noi trees.
2. The stock of Plau-Yai promoted the vegetative growth of the grafted Plau-Noi trees.
3. The stock of Plau-Yai was useful in controlling the root rot disease of the grafted Plau-Noi trees.

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Over the 1982-85 period we have been going with the investigations into sago palm forest in the Sepik River Basin, East Sepik Province, where“sago eaters”live.
Acreage of sago palm forest in this area amounts to 400, 000ha, ranginjg from natural stands to semi-cultivated stands. The vegetation including sago palm are divided into three types: sago palm phragmites swamp, sago palm swamp and sago palm forest. Semi-cultivated sago stands in sago palm forest are utilized by natives in a limited area.
Many of sago growing lands are distributed in low-lying swamps of the basin of river. The soils of these swamps cinsist of hydraquents, fluvaquents, and a part of histsols which are more or less the poor-drained alluvial soils. The ground water level changes seasonally, ranging from 1-2 meters deep from the surface during the minor rainy season to 50-60 cm above ground level with river floodwater during in the main rainy season. Over a distance of 80-90 km along Sepik River, staring from mangtrove forest to the upstream, Chlorine ion content was almost 40 ppm or bleow at all the survey points, which can be regarede as a fresh water area.
There was a large difference in air and ground temperature between the sunny exposed ground and the forest inside. It was shown that crowns of tall sago trees work to supress the temperature rise.

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