Fumitaka Shiotsu

Suppression of tillering in Erianthus ravennae (L.) Beauv. due to drought stress at establishment.

Abstract We investigated the effect of drought stress on biomass productivity of newly established Erianthus ravennae (L.) Beauv. This species has recently drawn great attention as a novel cellulosic energy crop because of its excellent tolerance against various environmental stresses, but the shoot dry weight of the newly established E. ravennae was significantly decreased under drought compared to irrigated condition. A significant correlation between shoot dry weight and stem number suggested that the drought-induced decrease in stem number was ascribable to the reduced shoot dry weight in the drought condition. Decrease in soil water content was coincident with mid-day decrease in stomatal conductance, suggesting that limitation of CO2 diffusion into leaf due to lower stomatal conductance in the drought condition caused decrease in photosynthesis followed by suppression of stem number. The present study suggested that E. ravennae was susceptible to drought, at least, in the first establishment year.

Effects of Reduction in Plant Height Induced by Chlormequat on Radiation Interception and Radiation-Use Efficiency in Wheat in Southwest Japan

Abstract The effects of reducing plant height by the growth retardant chlormequat on radiation interception and radiation-use efficiency in field-grown wheat were studied in southwest Japan. Chlormequat was applied to wheat cultivar Sanukinoyume 2000 at the beginning of jointing. The cumulative total solar radiation intercepted by the plant canopy (Si) was determined by continuous measurements of total solar radiation above the canopy with a dome pyranometer and below the canopy with tube solarimeters. Nondestructive measurement of leaf area index (LAI) and mean tip angle of the canopy (MTA) using a plant canopy analyzer was performed weekly. Chlormequat application shortened the culm length by 12.6% compared with the control, but did not affect the aboveground dry matter (AGDM), LAI, yield or yield components except for the harvestindex (HI). The extinction coefficient in canopy (K) was not affected by chlormequat, so that Si at heading and anthesis were not significantly different. Radiation-use efficiency (RUE) of chlormequat treated plants estimated from the slope ofalinearregression of Si vs AGDM was 1.34 g MJ-1 for the period up to heading and 1.57 g MJ-1 for theperiod up to anthesis. The RUE values were not significantly different between chlormequat-treated and control plants. Although the effect may be restricted to the duration from heading to the premature ripening stage, a higher MTA in chlormequat should provide a more even distribution of radiation within the canopy, which should increase the photosynthetic performance. These results suggested that shortening the culm length of this wheat cultivar by about 12% is beneficial in reducing the risk of lodging without affecting light interception characteristics or RUE.

Root-shoot relationships in four strains of field-grown Erianthus arundinaceus at seedling stage

Abstract The production of cellulosic bioethanol from non-edible plants is a potential countermeasure against global warming. Erianthus species provide cellulosic raw material for bioethanol because they have high biomass productivity and high tolerance to environmental stress, associated with their large, deep root systems. However, it is difficult to select Erianthus species for breeding by direct observation of their root systems because the roots are widely dispersed in the soil. Instead, we examined shoot morphological traits that could be closely related to root morphology to find effective reference indices for selection. The potential to evaluate root structure and function in Erianthus according to bleeding rate was also examined. An analysis of root–shoot relationships in seedlings indicated that root number and mean length were closely related to stem number and diameter, respectively. These results suggest that root–shoot relationships may provide useful criteria for selective breeding of root systems in Erianthus.

Effects of Partial Harvesting on Napier Grass: Reduced Seasonal Variability in Feedstock Supply and Increased Biomass Yield

Abstract The production of cellulosic bioethanol from non-edible plants is receiving increasing attention for its potential to avoid food–fuel competition. However, seasonal variability in feedstock supplies increases the costs of stockpiling and limits commercialization. The cellulosic energy plant Napier grass (Pennisetum purpureum) has conventionally been harvested three times per year (on a 4-month cycle) in Indonesia. To shorten this cycle, we examined an alternative system in which every four rows (rather than the entire crop) were alternately harvested every 2 months (partial harvesting). Results from a 20-month experiment indicated that partial harvesting was effective in shortening the supply cycle from 4 to 2 months. Moreover, partial harvesting significantly increased biomass yield, probably as a result of the border effect. Investigations into available light, atmospheric CO2 concentration, and soil volumetric water content suggested that partial harvesting allowed Napier grass to capture more light for biomass production.

Fate of 15N-labeled Inorganic Fertilizer in an Upland Soil Applied with Sweet Sorghum Bagasse and N Uptake Efficiency by Komatsuna Plants

Abstract Sweet sorghum bagasse (SSB) is a soil amendment with potential for biofuel production. This study was conducted to determine the appropriate techniques for application of SSB and the effect of incorporation of inorganic fertilizer (IF) on the production of komatuna (Brassica rapa) plants. SSB was applied to the surface of the plant or incorporated into soil. The N fate of IF was evaluated by using 15N-labeled IF. The combination of surface application of SSB and incorporation of IF to soil decreased the N uptake by komatsuna plants but increased dry weight, whereas the incorporation of IF and SSB gave lower komatsuna dry weight than IF treatment alone. Moreover, the application of SSB tended to increase the N distribution from IF to komatsuna with decreased N loss from the plant-soil system. These results showed that surface application of SSB is effective for increasing crop production due to reduction of N loss and improved N use efficiency.