Salinity is a major constraint to plant growth and development. Plants develop various organs such as salt glands to adapt to saline environments. Salt glands are located on the surface of shoots and excrete salts transported into the shoots. Almost all Poaceae plants, except for the subfamily Pooideae, possess bicellular trichomes called “microhairs”, and they act as salt glands in some species of the subfamily Chloridoideae. Salt glands in Poaceae contain distinctive structures that collect and excrete salts effectively. In addition to their contribution to salinity tolerance, these glands facilitate ion excretion, which plays a role in the circulation of elements and influences crop quality by altering the mineral concentration. This review describes diverse aspects of ion excretion via salt glands in Poaceae which includes many important crops and forage grasses, with a focus on recent findings.
Effects of temperature on yearly variation of rice thousand grain weight in 41 prefectures in Japan were analyzed for the last 19 years using the climate data published by the Japan Meteorological Agency and the statistical survey on crops published by the Ministry of Agriculture, Forestry and Fisheries. The temperature during the 4 weeks before heading in the 41 prefectures was from 20.6 to 28.8°C. In the 20 prefectures where the temperature during the 4 weeks before heading was less than 26.5°C , thousand grain weight tended to become smaller in the years when the temperature during the period was low. In the 6 prefectures where temperature during the 4 weeks before heading was less than 24.0°C, there was a high positive relation (p < 0.01) between temperature and thousand grain weight. This might be attributed to the small husk size due to the low temperature. On the other hand, in the 41 prefectures, the temperature during 4 weeks after heading was from 21.3 to 27.5°C. Then the relation between temperature during the 4 weeks after heading and thousand grain weight was not clear in most of these prefectures.
Production costs per unit area in rice cultivation can be lowered by reducing the number of seedling boxes either by increasing the seeding density per box or by decreasing transplanting density. The decrease in the number of seedling boxes, however, may lower grain yield and therefore may not reduce production costs per grain yield as much as expected. The objective of this study was to clarify the seeding density per seedling box and transplanting density that, when used together, minimize the production costs per grain yield in high-yielding cultivars “Ishikawa 65” and “Hokuriku 193”. In the 3 years from 2016 to 2018, we grew these cultivars at various seeding densities and transplanting densities, investigated their growth, yield and yield components, and calculated the production costs per grain yield based on the number of seedling boxes used. Grain yield was significantly smaller at the lower transplanting density but was not significantly affected by seeding density. The cost per grain yield was the lowest, when the density of seeding was 300 g per box and the density of transplanting was 21.2 hills per square meters, which required 9.2-9.8 seedling boxes per 10 a. The grain yield was highly correlated with the number of stems and growth index (the number of stems × plant height × SPAD Value) at the active-tillering stage in both cultivars.
The objective of this study was to clarify a vegetation index (VI) that could be the best measure for leaf nitrogen content of soybean canopy and identify the stages or periods at which the change in the VI positively correlates with seed yield. We investigated the relation between the nitrogen contents and VI in 2018 and 2019 and the relation between the VI and seed yield in 2019. In both years, plants were grown conventionally and in narrow rows, both at 2 or 3 planting densities. Soy fields were photographed with a multispectral camera and visible camera on an unmanned aerial vehicle. The images were reconstructed to generate ortho-images using the location information of the ground control points and VI maps of the fields were created. Nitrogen content of each organ, leaves, pods and others, were determined within 3 days after taking the photo. After seed maturation, we determined seed yield and VIs of the harvested areas. Among the VIs, GNDVI showed the highest coefficients of determination with the total nitrogen content and leaf nitrogen content but CIGreen was linearly related with those until the nitrogen content became high. Although CIGreen did not correlate with seed yield at any stage, we found highly significant positive correlations between seed yield and the change in CIGreen, delta CIGreen, in the periods of reproductive stages; the highest was the period between R1 and R5. Delta CIGreen (R1-R5) also showed highly significant positive correlations between the number of seeds and between 100-seed weight. These results suggest that seed yield of soybean could be speculated from delta CIGreen (R1-R5).
The dormancy of rice (Oryza sativa L.) seed varied by cultivar and year, and seed preparation using the conventional method often resulted in uneven germination. Therefore, we investigated the appropriate soaking conditions for securing uniformly germinated seeds by altering the temperature and duration of the soaking period. At the soaking temperature of 10°C or 12°C, the germination rate was 90% or greater when the accumulated temperature was 120°C or more for “Koshihikari” and 80°C or more for “Koshiibuki; and, the longer the duration of soaking, the higher was the germination rate of the deeply dormant “Gohyakumangoku”. When the soaked seeds were germinated in nursery soil, the longer the duration of soaking before sown in nursery soil, the percentage of normally germinated seeds was higher, and the length of the shoots was longer. However, at a soaking temperature of 5°C, the germination rate was less than 90% for “Koshihikari” and “Koshiibuki” and 50% for “Gohyakumangoku” regardless of the duration of soaking. The expression of α-amylase for each isoform was examined by western blotting after soaking at different temperatures and durations. AmyII-4 expression was observed at both 12°C and 5°C, but the transition of the expression during soaking varied with water temperature.
Crassulacean acid metabolism (CAM), the photosynthetic pathway that minimize water loss and the plants with CAM occupy hot and semi-arid regions. Recently, there has been increased attention to CAM plants that may serve as stable production under climate change and are cultivated for experiments. CAM plants live in variable environments on the earth as tropical epiphytes, halophytes, and aquatic macrophytes. Therefore, we would find them in variable environments in Japan. However, we have little information on the species and their habitats. In this study, CAM plants occurring in Japan are listed, especially the habitats, as a first step to understand the ecology of CAM plants by using domestic and foreign literature. There are 23 families, 83 genera, 237 CAM species in total in Japan. They are comprised of five submerged aquatic species of lycopodiophyte, Isotaceae, four epiphytic ferns of Pteridophyte, only one gymnosperm, Welwitschia mirabilis and in Magnoliophyta, one species of Piperaceae, 7 families 25 genera 86 monocots and 11 families 53 genera 140 eudicots. There are 185 cultivated species, which occupied about 80% of CAM species in Japan. There are also 56 native species in Japan, and almost of them live under water-limit condition such as on the rock or by the seaside. Although there are 33 naturalized species, CAM belonging to Rubiaceae and etc have not been found in Japan.
Aphanomyces root rot is a serious disease of sugar beet (Beta vulgaris L.) in poorly drained fields. This study was conducted to clarify the influence of cultivation methods on the disease intensity using a resistance cultivar cultivated by direct sowing or by transplanting in the Aphanomyces-infested field. As a result, there was no significant relationship between cultivation method and disease severity in 2018, because the root expansion was severely suppressed due to the high moisture condition. However, in 2019, the damage caused by disease in the plants cultivated by direct sowing was more severe than that in the plants cultivated by transplanting. In addition, root weight was significantly reduced in the plants cultivated by direct sowing compared to those cultivated by transplanting in both years. Hence it was suggested that the economical damage of Aphanomyces root rot was a more serious problem under direct sowing. On the other hand, the disease intensity of cultivars observed no significant differences under the two cultivation methods, the resistant cultivars “Hokkai_Mitsuboshi” and “Kachihomare” showed significantly superior disease indices and yield than the less resistant cultivars. These findings suggested that the damage caused by Aphanomyces root rot is serious in plants cultivated by direct sowing, and that utilization of a resistant cultivar would be an effective for its control.
Yukichikara’, ‘Ginganochikara’ and ‘Natsukogane’ are the wheat varieties most commonly grown in the cold regions of Japan. The characteristics of their spikes were compared in two locations: the Morioka and Joetsu. The spikelet number per spike was fewer for wheat in Morioka than that in Joetsu, whereas grain number per spikelet was larger in wheat of Morioka than in that of Joetsu. Although the wheat grown in both locations exhibited an increase in the grain number per spikelet from the base to the center of the spike and a decrease in number toward the top, the grain number per spikelet from the base to the center of the spike was larger in wheat of Morioka than in that of Joetsu. ‘Ginganochikara’ had fewer spikelets per spike than ‘Yukichikara’ and ‘Natsukogane’. However, ‘Ginganochikara’ was also characterized by a higher number of grains per spikelet than the other two varieties. The morphological differences noted among these varieties ware common to Morioka and Joetsu and the difference in the spike morphology between wheat from Morioka and Joetsu was considered to be due to the lower number of days and the lower effective cumulative temperature from seeding to completion of spike formation, in wheat of Morioka than in wheat from Joestu.
Nine Japanese paddy rice varieties were cultivated in a phytotron under a natural photoperiod with a day/night temperature regime of 30/22°C on Ishigaki Island which belongs to the subtropical climate, in the southernmost part of Japan. The sterility rates of all varieties were less than 10% when sown in June, but were higher for most varieties originating from the western region of Kanto when sown in September. September sowing accelerated the time to rice heading, resulting in shorter anthers and higher rates of sterility when anther lengths were less than 1.7 mm. Kyushu varieties (e.g., “Shinrei” and “Nishihomare”) had a short basic vegetative growth period and high photosensitivity. As these varieties generally have short anthers, when heading occurred noticeably earlier with September sowing, their anthers became even shorter and there was an increase in sterility. Tohoku and Hokuriku varieties (e.g., “Hitomebore” and “Fukuhikari”) have a long basic vegetative growth period and low photosensitivity. When sown in September, shortening of days to heading and anthers of these cold-resistant long anther varieties was negligible and their fertility remained high. The Kyushu varieties “Minaminishiki” and “Yumehikari,” which both have long anthers, maintained high fertility even when sown in September. Although both “Fukuhikari” and “Shinrei” were cultivated year-round, the sterility of “Fukuhikari” remained stable and low throughout the year, whereas that of “Shinrei” varied inversely with seasonal differences in the number of days to heading.
The sugarcane yield on Minamidaito Island is relatively low and unstable as it is highly dependent on climatic factors, particularly rainfall. In the present study, we calculated the water balance of ratoon-cane field on the island based on the meteorological data over the past 30 years and analyzed its relationships with sugarcane growth and yield. Water shortage was serious from July to September, with the insufficient water amount accounting for as much as 46% of that for a whole year, because the water consumption by sugarcane greatly exceeded the effective rainfall due to the low precipitation after rainy season. The insufficient water amount during the three months negatively correlated with stem elongation and cane yield, indicating that sugarcane growth and yield are significantly inhibited when exposed to drought at this stage. This trend was further clearer excluding typhoon years in which the maximum wind speed exceeded 25 m s-1. By using the regression equations in the non-typhoon years, it was found that each 100 mm increment in the insufficient water amount from July to September reduced stem elongation by 25.1 cm and cane yield by 14.1 t ha-1, respectively. The present study revealed that the water balance from July to September most strongly affects sugarcane growth and yield and that irrigation during this period is necessary to achieve high yields and stable production on this island.
This study was conducted to test a high yielding feed rice production system at a farmer’s paddy fields in the Nasu area of northern Tochigi Prefecture. This labor-saving and sustainable cultivation method uses sparse planting of “Oonari”, a high yielding indica cultivar, with cattle manure and controlled availability fertilizer. We applied manure at the rate of 2–2.5 kg m-2 and controlled availability fertilizer at the nitrogen rate of 12 g m-2, and obtained gross hulled rice yields of 879–920 kg/10 a. The numbers of spikelets per panicle were higher in the sparse planting than in the normal density planting. This increased the sink capacity, and likely increased the translocation of nonstructural carbohydrates to the panicles during the ripening stage, contributing to the high yields in the sparsely planted rice. The percentage of spikelets on primary and secondary rachis branches was not affected by planting density, which helped maintain the grain-filling ability. Vitamin E contents, including tocotrienol in the rice brans, did not vary with planting density. These results suggest that the sparse planting of “Oonari”, with cattle manure and controlled availability fertilizer, is an effective, labor-saving, and sustainable feed rice production system for the Nasu area.
In a cold climate region of Japan, we investigated the growth and yield of rice in Andosol by dry direct seeding cultivation using plowing and compaction (DS) compared with transplanting rice (TR). Leaf number and plant length were lower in DS than in TR at the early growth stage. SPAD value (leaf color) was lower in DS than in TR after the tillering stage. However, the aboveground dry weight in DS was not significantly different from that in TR. Although there was no significant difference in the number of panicles, the percentage of ripened grain was lower in DS than in TR and the number of spikelets per panicle was reduced in DS. The grain yield was lower in DS than in TR, and the grain yield per unit area was significantly correlated with the total number of spikelets. Moreover, the total number of spikelets was significantly correlated with the number of panicles. There were positive correlations between the number of spikelets per panicle and the SPAD value of the panicle formation and meiosis stages. These results suggest that to obtain a yield in DS similar to that in TR it is important to maintain SPAD values at the panicle formation and meiosis stages, as well as to maintain the number of panicles. Moreover, it is necessary to employ cultivation methods that increase the number of spikelets per panicle and the percentage of ripened grain.