The feasibility of near-infrared diffuse reflectance spectroscopic analysis (NIR analysis) for estimating the ratio of true seed weight to fruit weight (T/F) as well as water content was examined in sugar beet (Beta vulgaris L.) seeds of 61 F₁ hybrid lines and 4 standard cultivars. For the calibration, partial least squares (PLS) regression was carried out with second derivative spectra and the measured data using attached software (NSAS). For estimating T/F, calibration using 7 factors was the most valid with a correlation coefficient of calibration (R) of 0.943, standard error of calibration (SEC) of 1.26% and standard error of prediction (SEP) of 1.40%. By this calibration, sugar beet varieties could be classified into 4–5 levels according to the estimated T/F. For the estimation of the water content of sugar beet seed, calibration using 14 factors was optimal. The calibration was highly accurate since the R, SEC and SEP was 0.999, 0.23% and 0.27% respectively. Consequently, the true seed weight of sugar beet could be nondestructively and rapidly estimated by NIR analysis and weighing the air-dried seed. This technique should be useful in breeding selection for higher true seed weights, which would thereby improve the early growth of sugar beet varieties.

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Rice plants (Oryza sativa L.) were grown under normal (350 μL L^-1 CO₂) and CO₂-enriched (660 μL L^-1 CO₂) conditions, and ¹³CO₂ was supplied to the rice plants after heading to examine the translocation and partitioning of photosynthate at the early grain-filling stage. At 2 days after supplying ¹³CO₂, no difference in the ¹³C content of the whole plant was observed between the plants grown under normal and CO₂-enriched conditions, but translocation of ¹³C from the leaf blade to other plant organs seemed to be accelerated by CO₂ enrichment. Up to 9 days after supplying, ¹³CO₂ fixed into sucrose was mainly used to synthesize starch in the stem rather than translocated to the ear in plants grown under normal conditions. In contrast, the supplied ¹³C was rapidly translocated to the ear, and ¹³C stored as starch in the stem was also translocated to the ear in plants grown under CO₂-enriched conditions. Therefore, we concluded that CO₂ enrichment accelerated the translocation of carbohydrates to the ear.

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The adaptive responses of soybean and cotton to various irrigation levels were explored in terms of transpiration, stomatal role in transpiration, leaf temperature (T_L) and CO₂ assimilation rate (A_N). Compared with cotton, soybean showed a lower flow rate of stem sap (FRSS), transpiration rate (E), stomatal conductance (g_s), stomatal density and A_N and had a smaller stomatal area but larger leaf area, heavier root dry matter and higher T_L at all irrigation levels. Under water stress conditions, FRSS, E, g_s, and A_N decreased and T_L increased more in soybean than in cotton. Stomatal area decreased in response to water stress though nonsignificantly but stomatal density was not affected by water stress in soybean. Stomatal area decreased significantly in response to water stress in cotton. We concluded that soybean and cotton adapted to water stress differently. Soybean adapted to water stress by reducing transpiration while cotton adapted to water stress by maintaining higher transpiration as compared with soybean. Soybean reduced the transpiration rate by reducing g_s. Reduction of g_s in soybean was due to reduced FRSS, which might have resulted from the lower root moisture absorption efficiency. The higher transpiration in cotton was due to a higher g_s, which was supported by a higher FRSS, larger stomatal area, and probably the diaheliotropism. The higher g_s and transpiration rate suppressed the increase in T_L thus preventing the decrease of A_N in response to water stress.

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Leaf area of sago palm (Metroxylon sagu Rottb.) can not be estimated accurately from the whole leaf shape, and individual leaflet area must be measured for accurate estimation of leaf area. In this study we examined leaflet characteristics in detail and developed a method of estimating individual leaflet area. Shapes of all leaflets were similar regardless of their sizes. The leaflet width was maximal at the distal position around 30–40% from the leaflet base. Products of leaflet lengths and maximum widths (as the X-axis) showed almost a linear relationship with the leaflet areas measured with a leaf area meter (as the Y-axis). Moreover, the Y-intercept of the primary regression equation was very small compared to leaflet area values, and we can regard it as 0. We compared the measured leaflet area with the area of the ellipse with the leaflet length as the major axis and the maximum width as the minor axis. The difference between them was within±5% except for some leaflets at the base or tip of the leaf. These results suggested that the method of estimating leaflet area from the ellipse area calculated from the leaflet length and the maximum leaflet width as major and minor axes, respectively was simple and accurate. The estimation equation for the leaflet area is S(e)=0.785 L_Leaflet×W_Leaflet , where S(e) is the estimated leaflet area, L_Leaflet is the leaflet length, and W_Leaflet is the maximum leaflet width.

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Leaf senescence is slower in the soybean cultivar Tachinagaha (T) than in the cultivar Enrei (E). Reciprocal grafting of the two cultivars at the basal node showed that this difference was related to roots properties. However, roots had no effect on leaf senescence at a late stage of ripening. To investigate whether the properties of the above-ground parts of plants affect leaf senescence, we grafted the two cultivars at the internode between the 8th and 9th nodes of the stem. Regarding the effect of the scion on the stock, the chlorophyll content of leaves on the E stock was maintained at a higher level when the scion was T than it was E, and the chlorophyll content of leaves on the T stock decreased faster when the scion was E than when it was T. Regarding the effect of the stock on the scion, the chlorophyll content of leaves on the T scion decreased faster when the stock was E than when it was T, although the effect of the stock on leaf senescence of the scion were weaker compared with that of the scion on the stock. Differences in photosynthetic rate were similar to those in chlorophyll content. Thus, it was clear that leaf senescence was affected by the properties of both the higher and lower above-ground parts of plants, in addition to roots.

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The tolerance of three cultivars of rice (Oryza sativa L.) and three species of the genus Echinochloa to excess magnesium was examined in solution culture. In Echinochloa species, excess MgCl₂ or MgSO₄ in the culture solution (30 mM) reduced the growth to 33-42% of that in the control plants and caused symptoms resembling those of calcium deficiency. In rice cultivars, however, excess Mg in the culture solution reduced the growth only to 54-67% of that in the control and did not cause the symptoms like those of Ca deficiency. The effect of excess Mg on the mineral contents of plants differed between rice (Nipponbare) and Echinochloa oryzicola. The Mg content of the whole plants in rice increased in proportion to MgCl₂ concentration in the culture solution up to 30 mM, while that in E. oryzicola leveled off when MgCl₂ concentration exceeded 10 mM. The excess MgCl₂ treatment greatly reduced the calcium content of the whole plants in E. oryzicola and slightly in rice. In rice, the excess Mg treatment increased the Mg content of shoots and roots, and the potassium and chloride contents of roots, but slightly decreased the Ca and K contents of shoots. In E. oryzicola, the excess Mg treatment increased the K and Cl contents of shoots and the Mg and K contents of roots, and slightly increased the Mg content of shoots, but greatly decreased the Ca content of shoots. These results indicate that rice is more tolerant than Echinochloa to excess Mg and that the tolerance is related to Ca deficiency.

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The effects of day length on main stem growth, flowering, morphology of flower clusters and seed-set were examined in three buckwheat cultivars Shinanonatsusoba (summer eco-type), Miyazakizairai (autumn eco-type) and BLO 1999 (a long cluster line which usually develops DM clusters at Kade Research Ltd., Canada). Long-day treatment prolonged the stem elongation period, elevated the first flowering node, delayed the first flowering day, increased the numbers of nodes, flower clusters and flowers on the main stem, and decreased the increase rate of flowering-cluster number, the number of seeds and the seed-set ratio on the main stem. It also increased the frequency of DM clusters, the length of the flower clusters and the number of sub-flower-clusters per cluster in Shinanonatsusoba and Miyazakizairai as well as in BLO 1999. The effects of day length varied among the growth parameters and there were three types of responses to day length. The difference between the summer and autumn eco-type cultivars in the responses to day length was elucidated in four groups of parameters; (1) main stem elongation; (2) first flowering node and first flowering day; (3) increase rate of flowering-cluster number on the main stem; and (4) the number of seeds and seed-set ratio.

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The sink capacity (floret number per unit land area) is currently a serious constraint to grain yield production in japonica rice. The size and activity of the early reproductive shoot apex (incipient panicle) are potential determinants of the number of florets generated on the panicle. This hypothesis was tested using eight field-grown japonica rice cultivars (IR65598-112-2, IR65564-44-51, Nipponbare, Akenohoshi, Dobashi 1, Koshihikari, Kochihibiki and Nakateshinsenbon). Using morphometric microscopy, we found that the initial size of the reproductive shoot apex was highly correlated with the number of primary branches, but not with the number of florets per primary branch. The cell division activity of the early reproductive apex examined by in situ hybridization analyses using the histone H4 gene probe as a marker for DNA-replicating cells varied with the cultivar. Akenohoshi had twice as many DNA-replicating cells as Nipponbare and the cell division activity was highly correlated with the number of florets per primary branch, but not with the primary branch number. We concluded that the primary branch number was determined by the initial size of the reproductive apex, and that the floret number per primary branch was determined by the cell division activity in the following apex growth. This result provides the first evidence of a relationship between cell division activity and floret formation in the rice panicle.

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The variation in seed shape and husk color was investigated in 56 Japanese native cultivars of common buckwheat. Analysis of variance revealed highly significant differences among the cultivars in seed shape characteristics and husk colors. The 1000-seed weight (1000-SW) ranged widely, from 20.4 to 39.0 g, among the cultivars. The cultivars collected from the Kanto region of the mainland had a large length and width of seed and heavy 1000-SW. On the other hand, the cultivars from the Chugoku and Shikoku regions of Japan had a small length and width of seed. The length and width of seeds showed a high positive correlation. The cultivars with a high 1000-SW showed a slight difference between length and width of seed and were typically the triangular type in seed shape. The length/width ratio (L/W) depended on the width rather than the length of seed, though both were negatively correlated with the L/W. Highly positive correlations were found among the L*, a* and b* husk color value. The L* showed a highly positive correlation with growth duration, and the husk color of the cultivars became more deep black as growth duration decreased. The husk color of the cultivars from the Kyushu region (long growth duration) was grayish brown, but that of the cultivars from Nagano Pref. (the shortest growth duration) was characterized as typically deep black. The cultivars collected at lower latitude regions tended to have a lighter color of husk than those from higher latitude regions. The cultivars from the Tohoku region showed a smaller variation for seed size characteristics and 1000-SW, and the cultivars from the Kyushu region showed a smaller variation for husk color.

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This study clarified the effect of planting date on the growth and yield of potato (Solanum tuberosum L.) plants grown from conventional seed tubers (CT) and microtubers (MT). CT of about 50 g and MT of 1 to 3 g of early (Kitaakari) and late (Norin 1) maturity cultivars were planted at Hokkaido University, Sapporo, Japan, on May 13, June 4 and June 25, and their growth and yields were investigated. The linear increase in leaf area index started later, but thereafter was higher in MT plants than in CT plants, irrespective of cultivar and planting date. Tuber formation was later in MT plants than in CT plants of both cultivars, but this difference was smaller on the last planting date. The linear increase in tuber dry weight started later in MT plants than in CT plants, but the rate of increase was similar in MT and CT plants of both cultivars and on all planting dates. Delaying the date of planting reduced the tuber yield, mainly because of the shortening growing period in MT and CT plants. The reduction in tuber yield and growing period was greater for the late cultivar Norin 1 compared with the early cultivar Kitaakari of CT and MT plants. Despite the climatic variations among the planting dates, MT plants yielded 71 to 90% of tuber fresh weight relative to CT plants, suggesting that MT are a good alternative as propagules for potato cultivation in countries where seed production is difficult.

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Reduced tillage systems are gaining popularity but weed control is often a limiting factor in the adoption of such systems. Cover crops have become a viable option for sustainable agriculture because of its contribution to soil fertility and improved crop performance. However, the contribution of cover crops to weed management is not clearly defined. We compared minimum tillage (MT) and no-tillage (NT) with conventional tillage (CT) for their effects on wheat growth in an original paddy land clay soil in the presence of Chinese milk vetch as a cover crop. Cover crop biomass, weed emergence, main crop growth and yield and soil penetration resistance were examined. Chinese milk vetch was successfully established under MT and CT but not under NT, which retarded its growth resulting in a significantly large biomass of all weed species. Weed suppression was more effective when the cover crop was broadcasted than row seeded. The presence of milk vetch as a cover crop significantly suppressed weed growth under MT especially at the late stage of growth and resulted in a comparable grain yield to that under CT. Although soil penetration resistance under MT remained high throughout the period of wheat growth, milk vetch could be effectively utilized as a cover crop under MT and wheat grain yield under MT was comparable to that under CT without mulch treatment.

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Turmeric (Curcuma longa L ) plant species produces different sizes of daughter rhizomes (R) and mother rhizomes (MR), which are the only propagules (seed) for its cultivation. Here, we evaluated the effects of seed rhizome size on growth and yield of turmeric. Daughter rhizomes of 5-50 g (R-5 g–R-50 g) and mother rhizomes of 48-52 g (MR) were tested. The heavier the R up to 40 g, the better the plant growth, and the plants from the R-30 g, R-40 g, R-50 g and MR grew similarly well. The seed rhizomes with a greater diameter developed vigorous seedlings. The plants grown from R-30 g, R-40 g and R-50 g had a similar plant height, tiller number and leaf number, which were significantly higher than those from lighter R. The plants from R-30 g, R-40 g and R-50 g had a significantly larger shoot biomass and higher yield than those from smaller R in both the greenhouse and field experiments. R-50 g was easily broken at the time of planting, and had secondary and tertiary daughter rhizomes, which developed thinner plants and resulted in a lower yield. The shoot biomass and yield were highest in the plants grown directly from MR, and lower in the plants grown from daughter rhizomes attached to MR. This study indicates that the turmeric seed rhizome should be 30-40 g with a larger diameter, and seed mother rhizome should be free from daughter rhizomes.

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The effects of planting pattern and planting distance on the growth and yield of turmeric (Curcuma longa L.) were examined in Okinawa Prefecture situated in southern Japan. The dry weights of shoot and rhizome (yield) of turmeric planted in a triangular pattern were heavier than those planted in a quadrate pattern. A 30-cm-triangular planting resulted in the heaviest shoot and rhizome yield among the planting patterns examined. Dry weight of shoot per unit land area (m²) was significantly heavier when planted at a 20- and 30-cm spacing than when planted with a larger spacing, whereas the highest yield was obtained when planted at a 30-cm spacing followed by 20- and 40-cm spacing. When turmeric was planted at a 20-cm spacing, rhizome could not expand properly, which ultimately resulted in the smaller rhizome compared with that planted with a larger spacing. The highest turmeric yield coupled with the lowest weed biomass was obtained on the two-row ridge in a 75-100 cm width compared with a one- or two-row ridge in a larger or smaller width. This study indicates that for reducing weed interference and obtaining higher yield, turmeric should be planted in a 30-cm-triangular pattern on two-row ridge in a 75-100 cm width.

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