The effect of nitrate in the culture solution (0.7, 3.5, 7.0, and 14.0 mM N) on the growth, root nodule formation and nitrogenase activity of the peanut (cv. chico) inoculated with Bradyrhizobium sp. was examined at early developmental stages. The amount of nitrogen derived from fixation and its percentage to total nitrogen in the nitrate-fed plant were evaluated using 15N labeled nitrate. The dry weight and total nitrogen content of the plant at 40 days after transplanting (day 40) varied with the concentration of nitrate in the culture solution. Both of them were higher in the plants grown in the presence of nitrate at the concentrations above 0.7 mM. On the other hand, the number and fresh weight of nodules, and acetylene reduction activity per plant were the lowest in the presence of nitrate at 14.0 mM, relatively high at 0.7 mM, and the highest at 3.5 mM. The proportion of N derived from atmosphere to total nitrogen in the plants examined at days 18 and 33 was 23-31% in the presence of nitrate at 3.5 and 14.0 mM. However, the proportion examined at day 48 was as high as 57-58% at 3.5 mM, and it was only 22-24% at 14.0 mM.
The vigorous growth of tuberous roots of rooted sweet potato leaves caused not only the rapid increase in photosynthetic rate but also a considerable increase in leaf area. The rooted leaves of sweet potato can be an ideal source-sink model system to study physiological and biochemical control mechanisms of photosynthetic feed-forward effects on the source-sink balance.
Sucrose-phosphate synthase (SPS) activity in source leaves of potato plants (Solanum tuberosum cv. May Queen) transformed with maize SPS gene under the control of a modified cauliflower mosaic virus (CaMV) 35S promoter was two to four times higher than the endogenous activity found in the control. A negative correlation (r=0.82) between SPS activity and the ratio of starch to sucrose was observed. There were no significant changes in starch synthesis enzyme (ADGPase and QE) activities in the leaves. Photosynthesis did not differ significantly between control and transgenic lines. Aboveground (leaves and stem) and belowground (tuber) dry matter in three transgenic lines harvested during tuber development increased up to 15% and 20%, respectively, indicating that increased capacity for sucrose synthesis in potato leaves may lead to favorable growth. Moreover, the activity of this enzyme in source leaves of two transgenic potatoes increased when reaction temperature was elevated from 15°C to 35°C, a response similar to that of SPS in maize. Since temperature is a limiting factor for growth of potato, the transgenic plants will be useful for future studies under higher temperature growth conditions.
Ultrastructural changes of two different types of protein bodies Pb-I (spherical with concentric ring structure) and Pb-II (irregularly-shape without concentric ring structure), contained in rice endosperm during germination were studied with a transmission electron microscope and scanning electron microscope. Pb-I and Pb-II in rice seed endosperm began to decompose at the first day of germination. Protein bodies in the endosperm adjacent to the scutellum decomposed earlier than those at any other part of the endosperm. Rough and ditch-like holes were observed on the surface of the protein bodies at the second day of germination. According to transmission electron microscopic observation, Pb-I decomposed from the outside of each body, but Pb-II decomposed from the irregular parts of each body. Most of Pb-II had decomposed by the fourth day of germination, but the holes on the surface of protein bodies were not observed at this stage. After the fourth day, we observed few protein bodies remaining. According to transmission electron microscopic observation, vacuolated protein bodies were observed at the sixth day, and thereafter, each of the vacuolated protein bodies fused to develop large vacuoles.
The interaction between N application and water management (ordinary water (OW) and deep-water (DW)) in dry-seeded rice was studied in 1995 and 1996. Deep-water treatment increased the percentage of ripened grain and grain yield, and decreased panicle number per m2. The maximum number of tillers and the percentage of productive tillers was increased by increasing the amount of N applied (0, 70, 150, 220 kg ha-1) in both water treatments. More tillers was produced in OW than in DW. However, the percentage of productive tiller was higher in DW than in OW (78% in 1995 and 72% in 1996 for OW and 86% in 1995 and 83% in 1996 for DW). There were significant differences in yield components and yield between the amount of N applied, and between the two water treatments. The panicle number per m2 (r=0.904 in OW, r=0.921 in DW) was positively correlated with the amount of N applied. In DW, the number of panicles was lower than in OW, but the percentage of ripened grain was higher than in OW. The total nitrogen contents in the flag leaf was positively correlated with the amount of N applied and the concentrations of nitrogen in flag leaf was positively correlated with the grain yield. The partial factor productivity (PFP) of applied N was significantly higher in DW than in OW at all levels of nitrogen application. Agronomic nitrogen-use efficiency (ANUE) was not different between the two water treatments. These results imply that the suppression of tiller formation by elevated water level would improve the yield determinants and utilization efficiency of indigenous soil N, which consequently helps to increase yield production.
Growth and physiological characteristics of rice seedlings raised with long mat by hydroponics (SLH) were compared with those of young seedlings raised in soil (YSS). When SLH and YSS were raised under the similar environmental conditions, the dry weight of shoot in SLH was significantly lighter than that in YSS at the time of seedling harvest, whereas the shoot in SLH was as long as that in YSS. The increase of dry weight of shoot and the decrease of dry weight of grain were smaller in SLH than in YSS during the raising of seedlings. In addition, the content of soluble sugars in the grain of SLH was apparently lower than that of YSS, indicating that the supply of carbohydrates from endosperm to shoot was less in SLH than in YSS. Crop growth rate and mean leaf area index of SLH were lower than those of YSS, while net assimilation rate of SLH was similar to that of YSS. The size of leaf blades in SLH was markedly smaller than that in YSS, whereas no significant difference was observed in the rates of photosynthesis and dark respiration in leaf blades between SLH and YSS. The results suggest that the leaf growth of SLH is reduced by the insufficient supply of carbohydrates from endosperm, and this is the major cause of lower levels of dry matter production in SLH as compared with that in YSS.
Field experiments were conducted at the experimental field of Kyushu University, northern Kyushu in 1996 and 1997 to investigate the possibility of a double cropping of sorghum using early maturity cultivars. The effects of sowing date (early or late) and the cultivar on the yield were also examined. On the average, grain yield from double cropping was 556 g m-2 in 1996 and 746 g m-2 in 1997. Sowing date greatly influenced the major traits of the summer crop, but not significantly those in the spring crop, except for the days to heading. Late summer sowing decreased grain yield as much as 41.9% decreased 100-grain weight by 22.4% and extended days to heading. Early sowing, early in April and late in July or early in August, is recommended for spring and summer crops, respectively, in a double cropping system to obtain a high grain yield. SA 403, D12, C8, C9, D5 C10-1 F4 line and D5 × C8 (F1 hybrid) were considered to be suitable for a double cropping system.
Fifteen F1 hybrids derived from a six-parent diallel mating set (without reciprocal) of sorghum genotypes were used to investigate the combining ability for callus induction and plant regeneration. Anthers at a young stage were collected from the parents and hybrids, which were grown in a greenhouse, and cultured on a modified Murashige and Skoog medium containing 1.0 mg L-1 IAA, 2.5 mg L-1 2, 4-D and 2.0 mg L-1 kinetin. Calli of 2 to 5 mm in diameter were transferred to a regeneration medium containing 2.5 mg L-1 kinetin and 3.0 mg L-1 IAA for plant regeneration. The general combining ability (GCA) accounted for a larger proportion than the specific combining ability (SCA) for callus induction (179.83, mean square for GCA vs. 31.75, mean square for SCA) and for plant regeneration (1225.73, for GCA vs. 410.37, for SCA). Some parents and hybrids showed high callus induction ability accompanied with high green-plant regeneration ability. Thus, improvement of the rate of green-plant regeneration in anther culture through crossing and selection may be possible.
The Richards function, an asymmetric growth function, was fitted to germination data for several rice varieties, and functional parameters were transformed into stable population parameters that comprehensively characterize germination (viability Vi, time Me, dispersion Qu and skewness Sk). For practical purposes, the population parameters calculated using a symmetric logistic function were similar to those calculated using the asymmetric Richards function for the germination of rice plants. The reproduciblity of the calculated population parameters was so high that germination data can be measured at one-day intervals without replication. Therefore, population parameters can be applied as indices of the germination properties of a seed lot. Me was especially highly correlated with the establishment percentage, which indicates that it can be applied as a useful index of seed vigor. Although the emergence data could also be fitted to a logistic function, those for establishment should be fitted to the Richards function because the skewness becomes so large that population parameters can not be calculated exactly using logistic functions. Population parameters that show the properties of seedling growth are also available. For example, Qu of emergence shows the effect of seed soaking on the uniformity of emergence. In fields with fluctuating temperatures, the measured data fit better with the cumulative temperature than with time.
Banana shoots were cultured on the medium containing either one of the three gelling agents agar, gelrite and gellan gum for 13 weeks. The concentrations of the nutrient elements especially macro-elements, were higher in gelrite than in agar and gellan gum. Each of the three gelling agents had an optimal concentration for plant growth, but as a whole, shoot growth and multiplication was higher on the medium solidified with 0.9 g L-1 gelrite as compared with those on the medium solidified with 4-8 g L-1 agar or 2-6 g L-1 gellan gum. This may be attributed to the availability and uptake of water and mineral nutrients. Most of the shoots cultured on 0.7 g L-1 gelrite or 4 g L-1 agar and on the liquid medium showed poor growth and multiplication due to vitrification. The higher concentrations of gellan gum (6 g L-1) and agar (8 g L-1) did not support shoot growth and this was explained by reduced water and mineral salt uptake. At the concentration of each gelling agent that gave the best shoot growth and proliferation (gelrite 0.9, agar 6 and gellan gum 2 g L-1) the water potential of the medium was about -0.5 MPa and the medium with a water potential of about -0.6 MPa did not support plant growth. We concluded that the growth of banana plants in vitro was affected by the type and concentration of gelling agent mainly due to the difference in the physical properties of the medium.
In vitro direct shoot bud organogenesis from garlic (Allium sativum L. cv. White roppen) root tips was studied under a light microscope. In root tips cultured on the shoot induction medium that consisted of Murashige and Skoog basal salts and vitamins with 1 μM NAA and 10 μM BA, periclinal cell divisions were initiated in epidermal cells in the formative part or the distal elongation zone of the root apical meristem 6 to 8 days after the start of culture (day 6∼8). The periclinal cell divisions continued to form tiers of cells until day 12. Some of the cells divided anticlinally and formed protrusions of shoot primordia. Several shoot bud primordia developed within 16 days. Organized shoot apical meristems with leaf primordia were evident by day 20. The shoot bud formation in this study did not involve callus formation. The in vitro shoot bud formation from root tips could be efficiently used for the rapid clonal propagation of garlic without changing the genetic fidelity. The implications of developmental pattern in direct bud regeneration are relevant in developing suitable regeneration systems and conducting critical physiological experiments.