A survey of soybean fields in Hiroshima Prefecture revealed that the incidence of purple stain caused by Cercospora kikuchii in soybean (Glycine max (L.) Merr.) seeds has been significantly promoted by sowing seeds in the middle of rainy season (early-sowing) . The progress of disease on leaves of plants from early-sown seeds was more marked during the rainy reason, especially when the disease has already established before the onset of the rainy season. This promotion of disease development was recognized not only on the leaves but also on seeds and lasted until harvest time. This effect of early sowing of seeds has been attributed to the longer exposure of plants to the rainy season. Late-sowing, which is done in early July, had afforded the plants some time to escape the rainy season and hence, enabled them to be less prone to the disease. In addition, seed maturation period in early-sowing field was longer than that in late-sowing, and thus, exposing the seeds to a longer infectious period. These results indicate that late sowing of seeds can be used as a cultural practice for the control of this disease.

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Purple stain of soybean is a seed-borne disease. In soybean (Glycine max (L.) Merr.) cultivation where diseased defoliated leaves serve as an inoculum source of purple stain (Cercospora kikuchii Matsumoto et Tomoyasu), the removal of infected leaves from the field remarkably suppressed the disease incidence on growing leaves compared to the ordinary cultivation where leaves are left in the field. This practice delayed the infection of newly developed leaves, decreased the number of diseased leaves per plant and the number of lesions per diseased leaf. Consequently, this reduction of inoculum potential in the field significantly depressed the incidence of the disease on pods and seeds.

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The effect of temperature (15, 25, 30°C and glasshouse as control) at different growth stages (stage-I: vegetative to tuber initiation, stage-II: tuber initiation to initial tuber bulking and stage-III: tuber bulking to maturity) on leaf nitrate reductase (NR) activity, carbohydrate contents and tuber yield were investigated in potatoes (Solanum tuberosum L. cvs. May Queen and Normn 1) as pot experiment in naturally lit glasshouse and phytotron. The high temperature treatment decreased the total dry matter production as well as tuber yield and degraded the tuber quality by reducing the specific gravity. NR activity of leaves was also decreased by high temperature treatment, whereas low temperature increased the activity. Water soluble carbohydrate (WSC) and starch content in leaves were sequentially decreased and as a result total nonstructural carbohydrates (TNC) were also decreased by high temperature. The inhibition of tuber yield by high temperature was due to the limited translocation of carbohydrates from leaves to the tubers, following the reduction of NR activity and the expense of carbohydrates for dark respiration. The maximum yield reduction was observed at high temperature treatment at stage-I which was most critical for tuber yield, and low temperature at stage-II produced the highest yield which was considered as more advantageous step towards yield improvement.

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The effects of cytokinins added to MS media on the growth of apical and nodal stem segments of axillary branches of Gloriosa superba L. were examined. Survival rates of explants were increased by the addition of BA and TDZ. The optimal responses were obtained by addition of TDZ at concentrations higher than 0.3μM. Thidiazuron was effective on shoot and tuber formation in both apical and stem segment cultures. The optimal shoot proliferation was obtained at 3 and 10μM TDZ treatments (average number: 1.6/segment) . Higher number and rate of tuber formation were obtained in stem segments with TDZ at concentrations higher than 3 μM. The tuber formation markedly increased on MS medium at 10μM TDZ (average number: 7.8/segment, formation rate: 96%) .

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Corn steep liquor (CSL) is an industrial waste from corn starch factories. It is a browncolored viscous liquid, which contains many kinds of organic materials and about 3% each of N, P₂O₅ and K₂O. We examined the use of CSL as a liquid fertilizer. Calcium should be supplemented, because its calcium content is not enough for vegetable production. Tomato growth was possible through the application of the immature organic material but only if it was applied in small amounts frequently, within the decomposition ability of the soil. When CSL was applied in appropriate concentrations, plants grew normally : Shoot weight was about 80%, but the root weight was similar to inorganic liquid fertilizer application. Liquid fertilizer caused the change of root distribution : Both types of liquid fertilizer made the roots shallower than the basal dressing in the whole layer of the soil. This caused more water uptake in the surface layer of plant cultivated by liquid fertilizer. Organic liquid fertilizer made the root thicker than that of inorganic fertilizer. Liquid fertilizer application method is effective to reduce residual ions, especially for sulfate, calcium and magnesium, from the soil.

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The effects of nutrient, NaCl and heat stresses on the major cation (K, Ca and Mg) contents were studied in tomato (Lycopersicon esculentum Mill. cv. House Momotaro) seedlings. The purpose of the present work was to explore the similarity of cation responses under the above-mentioned stress conditions. Nutrient stress was applied by splitting the seedling roots into two parts, one of which was grown in 1/2 strength Enshi standard nutrient solution (ESNS) and the other was immersed in tap water. NaCl stress was conducted by treating the seedlings with 1/4 strength ESNS containing 150 mM NaCl for 1 week (1/4 strength ESNS without NaCl as control) . Heat stress was imposed by treating the seedlings at light 38°C and dark 33°C for 1 week (light 25°C and dark 20°C as control) . It was found that leaf K content was significantly decreased under both nutrient and NaCl stresses, while it was significantly increased under heat stress. Leaf Ca content was unaffected under both nutrient and NaCl stresses, but significantly increased under heat stress. Leaf Mg content was significantly increased under nutrient, NaCl and heat stresses.

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The effects of different temperature (15, 25, 30°C and glasshouse control) and moisture (75% FC, 60% FC and 45% FC) treatments at three growth stages (stage-I: vegetative to beginning of tuberization, stage-II: tuberization to initial tuber enlargement and stage-III: tuber enlargement to maturity) on net photosynthesis (PN), stomatal resistance (RS), transpiration rate (TR), dark respiration (DR) and leaf chlorophyll (SPAD value) were studied in several potatoes (Solanum tuberosum L. cvs. May Queen, Dejima and Normn 1) in pot experiments. Temperature at 25°C increased PN at all growth stages whereas 30°C treatment decreased the PN at all stages of growth. However, a decrease in RS and increase in DR, TR and leaf chlorophyll (LC) were observed under high temperature conditions. Similarly higher moisture (75% FC) increased the PN at all growth stages. But lower moisture decreased the DR, TR and increased the RS and LC. On total average, 17 and 37% PN, 18 and 37% TR, 26 and 41% DR decreased with the decrease of moisture level 60% FC and 45% FC respectively, over control (75% FC) . In the temperature treatments, 16% PN decreased by 30°C treatments, and 4 and 13% PN increased by 15 and 25°C temperature over control. Twenty percent TR and 35% DR increased by high temperature (30°C) treatments. PN decreased maximum at stage-II in temperature and stage-I in moisture treatment. From this study it can be concluded that moisture stress decreased more in the PN than that of temperature and leaf PN, RS, TR, DR, and LC are moisture as well as temperature dependent properties, and temperature 25°C is optimum for potato PN.

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Endosperm culture of ‘Tosa-Buntan’ pummelo, which was pollinated by ‘Suisho-Buntan’ pummelo, was performed to breed triploid pummelo. Sampling time of the endosperm and conditions of the culture medium for callus induction, proliferation and regeneration were investigated. Successful culture was obtained when the endosperm was taken 85 to 95 d after pollination and subjected to the culture under the following medium conditions (75% callusing) : basic MS medium (1/2 N) supplemented with 1% sucrose, 1μM BA and 5μM NAA. Sucrose concentrations between 3 to 7% were suitable for calli proliferation. Embryogenesis and rooting were induced from the calli by adding 30μM GA₃ to the basic MS medium, though the best medium condition was still unclear. Endosperm callus was estimated to be triploid by the use of ploidy analyzer. Chromosome numbers of the adventitious root tip generated from callus was confirmed as 2n=3x=27 under microscope. Therefore, it was considered that triploid plants would be generated through endosperm culture of ‘Tosa-Buntan’ pummelo.

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The objectives of this study were to estimate 1) the net photosynthetic rate of sweetpotato plants canopy (P_cn) using Monsi and Saeki's mathematical model, and 2) the increase in dry weight of plants in closed-type transplant production system. The P_cn 2, 6, 9, 12, 13 and 14 d after planting were estimated to be 2, 8, 10, 17, 18 and 17 μmol m^-2 s^-1, respectively. Measured and estimated values of increase in dry weight per plant for 15 d were 337 and 357 mg, respectively. The maximum light utilization efficiency (P_cn divided by photosynthetic photon flux (PPF) on the tray surface) 2, 6, 9, 12, 13 or 14 d after planting was found at the PPFs of 10, 191, 260, 321, 323 or 360 μamol m^-2 s^-1, respectively. Hence, the electric energy consumption for lighting was reduced by 35% when PPFs were set at 50, 200 and 300pmol m^-2 s^-1 O-4, 5-8 and 9-14 d after planting, respectively, as compared with a constant PPF of 300μmol m^-2 s^-1, under the present experimental conditions. These results indicate that the mathematical model for estimating growth of sweetpotato plants can be applied to the energy conservative control of the environment (e.g., PPF) in the closed-type transplant production system.

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Sweetpotato plants were grown for 15 d under stepwise photosynthetic photon flux (PPF) and two levels of constant PPF conditions. In stepwise PPF condition, the PPFs were set at 100, 200 and 300μmol m^-2 s^-10-4, 5-9 and 10-14 d after planting, respectively. PPFs of 200 and 300μmol m^-2 s^-1 were chosen as the constant PPF conditions. Under same integrated PPF (PPF×photoperiod×experimental period), dry weight per plant 14 d after planting was 1.1 times higher in stepwise PPF condition than in constant PPF condition. The increase in dry weight per electric energy consumption of lamps was 1.1 times higher in stepwise PPF condition than in constant PPF conditions. Therefore, stepwise PPF control is a useful method for reducing electric energy consumption and increasing electric energy utilization efficiency (chemical energy contained in plants/electric energy consumption of the system) of the closed-type transplant production system.

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The purpose of this paper is to clarify quantitatively the effects of pH and available chlorine concentration (ACC) of electrolyzed anode-side acid water on powdery mildew (Erysiphe cichoracearum de Candolle) infection (PMI) and occurrence of a leaf burn-like physiological disorder (LBLPD) in tomato (Lycopersicon escukntum Mill. cv. Momotaro) . For this purpose, the following three types of pH-ACC-regulated water were sprayed once every 3rd or 4th day, 5 times in total at 3 to 4 d intervals, to expanded leaves of tomato plants grown in a glasshouse, and then the severity of PMI and the percentage of leaves with LBLPD were investigated : pH regulated water (pH 2.1, 2.3, 2.5, 2.7 or 7.0; ACC 0 mg L^-1), ACC-regulated acid water (pH 2.5; ACC 0, 20, 30, 40 or 50 mg L^-1), and ACC-regulated neutral water (pH 7.0; ACC 0, 20, 30, 40 or 50 mg L^-1) . The pH and ACC of the regulated waters were adjusted with HCl or NaOH and NaClO solutions, respectively. The severity of PMI was evaluated as the increment in severity (severity increment, ΔS) from immediately before the first spray treatment. The PMI investigation showed that compared to the control (no spray) and distilled water spray treatment, each of the following three conditions significantly contributed to controlling PMI on tomato leaves : 1) pH of 2.7 or lower (more effective at lower pH) ; 2) the combination of pH of 2.5 and ACC of 20 mg L^-1 or higher (more effective at higher ACC) ; and 3) ACC of 50 mg L^-1. The LBLPD investigation showed that compared to the control and distilled water spray treatment, each of the following two conditions significantly contributed to causing LBLPD on tomato leaves : 1) pH of 2.7 or lower (more sever at lower pH) ; and 2) ACC of 20 mg L^-1 or higher.

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The incidences of overgrowth and unmarketable fruits were compared between tomato autografts planted with 50 mL plug and those with 800 mL pot (control), and the regulation of such incidences were tried with Solanum rootstocks. Planting with plug promoted the early growth of tomato plants and the growth was regulated by Solanum rootstocks. S. melongena rootstock suppressed the overgrowth and kept vigor similarly to that of the control autograft, whereas S. integrifolium and S. torvum rootstocks decreased the growth more than S. melongena. Thickening and aerial rooting at scion base, phenomena of graft incompatibility, were observed in the heterograft on S. torvum. Marketable fruit weight was lower in planting with plug than that with pot in tomato autografts, but unmarketable fruit weight, especially cracking fruits, markedly increased by planting with plug. Among grafts on various rootstock species, marketable fruit weight was the largest in S. melongena rootstock and the smallest in S. torvum rootstock. The marketable fruit weight of the heterograft on S. melongena planted with plug was similar to that of control plants. Planting of the tomato plugs decreases marketable fruit yield through cracking of the fruits. However, such deteriolation is ameliorated by S. melongena rootstock.

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The effects of NH₄⁺ : NO₃^- in culture medium on growth and nutrient absorption of Phalaenopsis seedlings in vitro were investigated. Leaf number decreased at 8 : 2 and 10: 0 of NH₄⁺ : NO₃^- (N ratio), and leaf area increased at 0 : 10 and 2 : 8 N ratios. Root number and root length were linearly decreased with increasing NH₄⁺ ratio. Consequently, possibility to control root growth by incubating on the medium with 2 : 8 N ratio without suppression of leaf growth was indicated. Although nitrogen absorption was not affected by N ratios between 0 : 10 and 4 : 6, P, K, Ca, and Mg absorption were remarkably decreased with increasing NH₄⁺ ratio. NH₄⁺ antagonistically inhibited Ca and Mg absorption. Thus, growth and nutrient absorption of Phalaenopsis seedling in vitro were promoted by incubating in culture medium containing NO₃^- as sole nitrogen source.

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