Asymmetric distribution of acetylcholinesterase (AChE) activity has previously been demonstrated to occur in the lower side of the gravity-stimulated maize shoot. The localization of immunoreacted IAA-inositol synthase, AChE and safranin was detected in selected organs of gravistimulated dark grown maize seedlings using a light microscope. Immunoreacted IAA-inositol synthase was asymmetrically distributed in the lower side of the stele of coleoptile node and mesocotyl in maize seedlings placed horizontally. The positive AChE spots in the coleoptile node and mesocotyl were apparently localized in the lower half of the gravistimulated seedlings. Safranin was also asymmetrically distributed in the lower half of the endodermis and stele cells of coleoptile node and mesocotyl. Namely, transport of safranin in the upper half of the coleoptile node and mesocotyl was blocked by gravistimulation. Furthermore, the asymmetric distribution of immunoreacted IAA-inositol synthase was inhibited by neostigmine bromide, AChE inhibitor. These results show that an asymmetric environmental stimulus induces changes in AChE activity, affecting IAA-inositol synthase localization and safranin transport.
To characterize the protection effect of silicon against excessive transpiration in rice plants (Oryza sativa L.), we investigated the factors responsible for transpiration, such as cuticular conductance (gc), leaf surface wax content(WC), and stomatal movement in response to environmental stimuli, using leaves of plants grown in nutrient solution with silicon (+Si) and without silicon (-Si). The rate of transpiration of whole plants (E) under field conditions was clearly reduced by application of silica. The gc of -Si leaves under precisely regulated conditions was 33% higher than that of +Si leaves, reflecting higher adaxial gc. Silicon has little effect on WC, a factor responsible for regulation of cuticular resistance to water flux in rice leaves. These results suggest that silicon is one of the main factors responsible for regulation of gc, but that its effect was not due to an increase in the WC. Leaf conductance (gl) of -Si leaves tended to decrease more slowly than that of +Si leaves over time after changes from high to low light intensity. Moreover, it was always higher over the entire duration of the experiment, irrespective of irradiation intensity. The gl of -Si leaves was higher at lower relative humidity (RH) and the initial response to a subsequent increase in RH was slower than that of +Si leaves. A comparison of gl and gc between +Si and -Si leaves showed that the higher gl of -Si leaves was due to higher stomatal conductance. These results indicated that the reduction in E by application of silica was mainly attributable to reduction in the rate of transpiration through stomatal pores.
To evaluate the positive effects of silicon on the stress tolerance of rice plants, we measured the electrolyte leakage (El) from leaf tissue caused by desiccation with polyethylene glycol (PEG) and by high temperature to estimate the integrity of cell membranes. The El caused by 30% and 40% solutions of PEG decreased with the increase in the level of Si in leaves. In leaves of plants grown with 100 ppm SiO2, the level of polysaccharides in cell walls, which is one of the factors related to tolerance to desiccation, was 1.6-fold higher than that in leaves of plants grown without Si. Ultrastructural observations of leaves revealed that polymerized Si accumulated in the walls of epidermal cells but not in those of the mesophyll cells, which are probably the main sites of El. These findings suggested that silicon in rice leaves is involved in the water relations of cells, such as mechanical properties and water permeability and plays a role in preventing El through the synthesis and functions of cell walls. The El caused by high temperature (42.5°C) was also lower in the leaves grown with Si than in the leaves grown without Si, suggesting the involvement of silicon in the thermal stability of lipids in cell membranes. These results suggested that silicon prevents the structural and functional deterioration of cell membranes when rice plants are exposed to environmental stress.
The dark respiration rates (Rr;CO2 efflux rates per unit dry weight) in the whole plant, leaves, stems and panicles of rice, grown in the field, were measured in 1991 and 1992. In both years Rr in the whole plant was highest at the start of measurement (rooting stage), decreased rapidly thereafter until the heading time and then gradually during the ripening period. Rr in leaves after the end of leaf expansion and that in stems during the ripening period was nearly constant. This implies that Rr in the matured plant organs shows only a small variation. Although the temperature coefficient (Q10) of Rr was 2.06 on the average, it changed during the growth period and differed with the organ. The growth efficiency, GE=ΔW/(ΔW+R) (ΔW;increase of dry matter, R;respiratory loss) was above 60% during the early growth period, but decreased thereafter, and rapidly at the late ripening period. This decrease in GE is considered to have been caused by the increase in maintenance respiration which is not related to dry matter production. Although respiratory loss was almost the same in 199 1 and 1992, the GE at the late ripening stage was higher in 1992 (35%) with longer sunshine hours than in 1991 (5%). This means that decrease in GE was mainly caused by the decrease in gross photosynthesis. Translocation of large amount of carbohydrates was assumed to cause the decrease in GE of the whole plant.
Two Bupleurum falcatum cultivars, which originated from Jeongseon, Korea and Kumamoto, Japan were grown for two years to clarify the dry matter (DM) production, efficiency for solar energy utilization (Eu) and saikosaponin a, c and d contents in Fukuoka, Japan. Aerial parts, root and total DM production differed with the cultivar both in the first and second years. Generally, DM production correlated with leaf area index, and there was a significant relationship between total DM and Eu in the plants of the first year in both cultivars. High Eu was observed at the flowering stage in both cultivars in both years. The maxium Eu was 1.02-1.23% in the first year and 1.16-2.09% in the second year. Total saikosaponin content was higher in the first year than in the second year. Although the total saikosaponin content was higher in Jeongseon cultivar than in Kumamoto cultivar in the second year, no difference betweeen the two cultivars was observed in the first year. We concluded that annual cultivation with a high saikosaponin content was preferable for the high yield of saikosaponin.
Three pot experiments were conducted to investigate the effects of soil amendment with crab shell on (1) soybean (Glycine max Merr., cv. Akishirome) yield after 120 days outdoors, (2) soybean nodulation after 6 weeks in the greenhouse, and (3) soil chemical properties after 10 weeks in the greenhouse. The experimental treatments were addition of crab shell at rates of 0.1, 0.2, 0.3, 0.5, and 1% (w/w), standard fertilizer (NPK) treatment, and an untreated control with neither crab shell nor fertilizer application. The crab shell amendment treatment was applied either two months before seeding (incubated) or immediately before seeding (non-incubated). The soil used was a volcanic ash soil (Andosol) from Kakamigahara. Addition of crab shell just before seeding caused a significant increase in seed yield and 100-seed weight compared to the control, but similar yield to NPK treatment. However, seed yield and 100-seed weight did not differ with the crab shell application rate. Amendment by 0.1-0.3% crab shell without incubation lead to the formation of slightly more nodules than in the NPK and control treatments. Reduced numbers of nodules were observed in soil incubated at 0.5- 1%, and in non-incubated soil with 1% crab shell application. Nodule fresh weight and N2-fixation plant-1 were decreased in all incubation treatments and 0.3-1% non-incubation treatments as compared to the NPK treatment and the control. Both nodule fresh weight and N2 fixation were lower in incubated soils than in non-incubated soils, at corresponding rates of crab shell treatment. Dry matter production of soybean plants in soil given the crab shell treatment, especially when incubation was used, was found to be reduced after 6 weeks of plant growth. EC, N, and P availability increased with the increasing rate of crab shell treatment. However, there was a gradual decrease of soil pH following the crab shell treatment. In conclusion, although soybean nodulation and N2 fixation were not improved by crab shell application, seed yields were similar to those obtained with the NPK fertilizer.
The physicochemical and mochi-making properties of native red and black-kerneled glutinous rice (RKGR) and white-kerneled glutinous rice (WKGR) of japonica and indica varieties, were examined. In both the japonica and indica varicties, RKGR cultivars contained more protein than WKGR cultivars, the difference being 2.1% and 1.9%, respectively. In both varieties, no significant difference in amylose contents of RKGR and WKGR was observed. The amylographic characteristics of RKGR varied considerably with the variety. In the japonica variety, RKGR cultivars tended to have higher mean maximum viscosity and breakdown values than WKGR cultivars, although the difference was not significant. By contrast, in the indica variety, the mean maximum viscosity and breakdown values of RKGR cultivars were significantly (p<0.05, t-test) lower than those of WKGR cultivars. In both varieties, the difference in gelatinization temperature between RKGR cultivars and WKGR cultivars was not significant. Cooked RKGR cultivars had a higher hardness and a higher hardness/adhesion ratio than WKGR cultivars, although a significant difference between the adhesion of RKGR cultivars. The hardening speed of mochi made from RKGR cultivars tended to be lower than that of mochi made from WKGR cultivars. The hardening speed of mochi showed a significant positive correlation, with the atmospheric temperature during the ripening period. The palatability of mochi of RKGR cultivars in both varieties tended to be inferior to that of WKGR cultivars. The particularity of physicochemical and mochi-making properties of RKGR cultivars is considered to be excellent as the processing material and to develop new processed-rice products.
Unlike the parent line, the hybrid calli between C3 and C4 species of Amaranthaceae have poor division capability. Therefore, in this study the fine structures of hybrid callus derived from protoplasts of Celosia cristata L. cv. Pink Charm (C3 species) cell suspension and Amaranthus tricolor L. cv. Perfecta (C4 species) cotyledon callus were investigated by light and electron microscopy, and compared with the parental. All callus lines were composed of parenchymatous cells possessing a voluminous vacuole. Parental callus lines contained organelles with a relatively normal structure. The peculiar feature characterizing the C3/C4 hybrid callus was the presence of highly lobed nucleus with multinucleoli and numerous small vacuoles having autophagic activity scattered in the cytoplasm. The autophagic activity is apparently related to the existence of several inclusions such as cytoplasmic organelles in the central vacuole. It might also be related to the pronounced expansion of central vacuole and the reduced cytoplasm. The failure to sustain proliferation related to some atypical features of the organelles is discussed.