The effects of soil amendment with oilseed-rape residue (OSRR) and chicken manure (CM) on the growth and nitrogen (N) uptake of faba bean (Vicia faba L.) were assessed in a pot experiments with Italian ryegrass (Lolium multiflorum Lam.) as a reference crop. A 15N isotope dilution method was used to estimate the amount of N derived from the residue (OSRR and CM) and from atmosphere through N2 fixation in the plants. Dry weights (DW) of shoots and whole plants were heaviest in the plants grown on the soil amended with CM (CM plants) followed by the plants grown on the soil amended with OSRR (OSRR plants) and control plants in this order. There were significant differences (p<0.05) in dry weight between CM, OSRR and control plants. DW of roots was also increased by amendment with either CM or OSRR in faba bean, but it was decreased in ryegrass. The amount of total N in both roots and shoots were increased by application of either CM or OSRR in both faba bean and ryegrass. The amount of N2 fixed by faba bean cultured on 1.2 kg soil amended with 10g residue (CM or OSRR) was 85.9 mg pot-1 but total N in faba bean derived from OSRR and CM was 192 and 374 mg pot-1, respectively. The percentage of N derived from atmosphere to total N in faba bean plants ranged from 15.9 to 26.5%. The amount of N taken up by faba bean and ryegrass plants from CM were larger than those from OSRR by 81.0 and 54.3%, respectively. Soil N balance was calculated as the difference between the amount of N applied (including fixed) and taken up by the plants. The N balance of soil amended with OSRR after cultivation of faba bean was 72.2% higher than that of the soil amended with CM, and that after cultivation of ryegrass was 89.9% higher.
The effect of growth under elevated CO2 on the capacity of photosynthesis was assessed in two cultivars of radish, Raphanus sativus L. cv White Cherrish and Kosena, with a large and small storage root, respectively. Plants were grown under ambient (ca. 350 mmol CO2 mol-1) and elevated (ca. 750 mmol CO2 mol-1) CO2 and the first leaf of the plants at various ages, were examined for chlorophyll fluorescence, the maximum photosynthetic rates under saturated CO2 (photosynthetic capacity) and the rates of transpiration simultaneously. Elevated CO2 did not significantly reduce the capacity of photosynthesis, transpiration, quantum yield of electron transport from photosystem II (ΦPSII), and the maximum intrinsic yield of photosystem II at any developmental stage in both cultivars. In other words, growth under elevated CO2 had no effect on the capacity of photosynthesis in either cultivar. These results suggested that not only the storage root but also vigorously growing young leaves play an important role as a sink in utilizing increased photosynthate under elevated CO2. The elevated CO2 accelerated ontogeny and caused a slightly earlier decline in the capacity of photosynthesis. The capacity of carbon metabolism and the photochemical capacity decreased coordinately with advancing age accompanied with the decline of photosynthetic activity under both ambient and elevated CO2.
The effects of elevated CO2 (approximate doubling of atmospheric CO2 concentration) on the rate of photosynthesis estimated from continuous monitoring of CO2 exchange in whole plants were investigated in radish cv. Kosena accompanied with simultaneous analysis of growth for 6 days from 15 to 21 days after planting (DAP). The elevated CO2 increased the dry weights of hydroponically grown radish plants by 59% at 21 DAP. The increase in dry weight was due to a combined effect of increased leaf area and increased photosynthetic rate per unit leaf area. Leaf area and the photosynthetic rate were increased by elevated CO2 by 18-43% and 9-20%, respectively, during 15 to 21 DAP. Namely, an increase in the rate of photosynthesis is accompanied by an increase in leaf area, both having a significant effect on biomass production.
Reflectance and polarized reflectance in the visible red band were measured for wheat canopies in a wide range of solar zenith angles to explore the relations among reflectance and polarization, view and illumination geometry, and crop canopy development. The reflected sunlight in a 10° field of view was measured with a radiometer at approximately 1.6 m in height. The view zenith angles were set from 0° to 75° at 15° intervals, and the observation azimuth was towards the sun. The relation between the polarization and solar zenith angle depended both on the view zenith angle and the growth stage. Multiple regressions were applied to estimate the polarization and reflectance at solar zenith 40°. Seasonal profiles of LAI, leaf inclination distribution, reflectance, and polarized reflectance indicate that polarization includes information for canopy structure such as leaf inclination distribution. Observations at solar zenith angles of more or less than 40° may also give similar results when the view zenith angle is appropriately set, corresponding to the solar zenith angle at the time of measurement.
Duration of the drought period is important for plant response during drought and after rewatering. We hypothesized that, if drought duration is extended, (1) high seedling vigor and rapid development of a deep root system will not be advantageous, and (2) osmotic adjustment will be more important. Six diverse rice (Oryza sativa L.) genotypes were selected from rainfed lowland germplasms to examine the development of a deep root system and osmotic adjustment, and their relationship with biomass production during drought and after rewatering, under two different drought durations (shorter and prolonged) in the greenhouse. NSG19 and KDML105 had greater seedling vigor (larger seedling biomass), developed a deep root system earlier in response to drought, extracted soil water more quickly, and their pre-dawn leaf water potential declined more rapidly during the prolonged drought period. These two genotypes showed superior drought recovery even after a prolonged drought period in which they suffered a greater reduction in transpiration, water use efficiency, and biomass production. The superior recovery ability was associated with larger plant size by the end of the drought period rather than with plant water status during drought, such as osmotic adjustment or leaf water potential. Osmotic adjustment was greater during prolonged drought periods (ca. 0.7 MPa) than during shorter drought periods (ca. 0.5 MPa), and lower osmotic adjustment was mostly associated with a higher leaf water potential. Genotypic variation in osmotic adjustment was observed, but there was no clear relationship between osmotic adjustment and biomass production during drought periods. These patterns of response of rice seedlings to drought and rewatering in the greenhouse should help to explain the patterns of adaptation of rainfed lowland rice in the field. Selection for drought recovery ability should be an advantageous strategy for early season drought.
The objective of this study was to clarify the changes in the contents of endogenous carbohydrates and proline in the stolons and leaves of centipedegrass (Eremochloa ophiuroides (Munro) Hack.), during the natural cold acclimation (hardening) and de-acclimation (dehardening) in relation to freezing tolerance in the field at the transition zone between temperate and subtropical areas in China. The contents of carbohydrates and proline, and freezing tolerance estimated by LT50, which is the temperature at which 50% of the electrolytes in the organ was measured in the leachate, were determined at 10-day intervals from October 1, 2001 to April 18, 2002. It was indicated that the freezing tolerance of stolons increased (LT50 of stolons decreased) quickly, as temperature dropped before winter, but that of leaves which senesced along with the drop in temperature did not. The freezing tolerance of stolons decreased gradually along with the rise in temperature above 5 °C in spring, when the overwintered plants started to grow. The contents of proline and soluble carbohydrates, including sucrose, fructose and glucose, increased as LT50 decreased when temperature dropped below 5 °C before winter, and decreased as LT50 increased in early spring. Correlation analysis revealed that the freezing tolerance of stolons of centipedegrass significantly and positively correlated with the contents of proline and soluble carbohydrates, and the ratio of the soluble carbohydrates to starch. Thus, the freezing tolerance of stolons, which are critical organs that determine the winter surviving ability, largely depended on the content of soluble carbohydrates and the ratio of soluble carbohydrates to starch in centipedegrass. The possible relationship between freezing tolerance and carbohydrate metabolism was also discussed.
Deep root penetration, which allows access to deep soil water and hydraulic lift, may help plants to overcome drought stress. The aim of this study was to evaluate the ability of sixteen food crop species to take up water from deep soil layers and the extent of hydraulic lift by the use of deuterated water. Plants were grown in pots consisting of two loose soil layers separated by a hardpan and a Vaseline layer. The lower (deep) layers were always kept wet (32%; Ψ= -5 kPa), while soil moisture in the upper (topsoil) ones was adjusted to 25% (Ψ= -7 kPa) and 12% (Ψ= -120 kPa) in the well-watered and drought treatments, respectively. The deuterium labeling of the deep soil water provided evidence that wheat, Job's tears, finger millet, soybean, barnyard millet, rice, and rye (in decreasing order of D2O increments) extracted more water from the deep layers under drought than well-watered in topsoil. These species showed significantly greater hydraulic lift under drought, except for soybean. Most of these species also showed increased root length density in deep soil layers and sustained high photosynthetic rates under drought. In contrast, pigeon pea, cowpea, common millet, pearl millet, foxtail millet, maize, barley, and oat did not show a significant increment in either deep-water uptake or hydraulic lift under drought. In summary, increased extraction of deep soil water under drought was closely related with the magnitude of hydraulic lift.
We investigated the effects of pretreatment with a low concentration of methyl viologen (MV) on the salinity-induced chloroplast degeneration in rice seedlings. The seedlings grown in hydroponic culture containing nutrient solution for 3 wks were treated with 100 nM MV mixed in the hydroponic culture for 3 days, and then with 200 mM NaCl without MV for 3 days. In the plants without MV pretreatment, the chlorophyll content drastically decreased during the NaCl treatment accompanied by swelling of thylakoids and destruction of thylakoid membranes. These damages were alleviated by the pretreatment with MV. The activities of CuZn-SOD and Fe-SOD, which localize in chloroplasts, increased under salt stress in both plants with and without MV pretreatment. In the plants under salt stress without MV pretreatment, ascorbate peroxidase (APX) activity did not differ from that of control. However, in MV-pretreated plants, APX activity under salt stress was about 1.2- to 1.3-fold higher than that of the control. Catalase (CAT) activity in NaCl treated plants was decreased to 52% of the control and the reduction in CAT activity was suppressed by MV pretreatment. These results suggest that MV reduced the damages by salt stress in chloroplasts by increasing APX activity and preventing the decrease in CAT activity.
We cultivated sweet sorghum cultivars –Wray, Keller and Rio – to confirm the feasibility of cultivation in dry land of Indonesia for monosodium glutamate (MSG) production. Stem yield of Wray was 4,790 – 6,593 g m-2. Sweet sorghum reached anthesis at 73 days after sowing (DAS) and was harvested 3.5 months after sowing. Stem length increased to 36 DAS, then rapidly to 320 cm by 80 DAS. Stem diameter reached 18 mm by 36 DAS. Stems enlarged for 1 month, then elongated. Thinning and weeding for 1 month after sowing produced heavy-stem plants with high yield because stem length and diameter determine stem volume and yield. Stem sugar weight increased after anthesis and reached a peak at 26–3 days after anthesis (DAA). Grain grew until 26 DAA and dried. It was harvestable after 30 DAA. Stem sugar content closely correlated with Brix indicating its value as an index of sugar in stem juice. Consequently, the optimum harvest time is determined by measuring Brix after 30 DAA (103 DAS). Yields were highest in cv. Wray: stems (4,790 g m-2) and sugar (286 g m-2). The juice extraction rate was ca. 50% by single-step milling without imbibition water. Using imbibition water and multiple milling steps can provide more than 400 g m-2 of sugar with a greater than 75% juice extraction ratio. Grain yield of other cultivars was similar to cv. Wray's 238 g m-2. Sweet sorghum could be cultivated on dry land in the rainy season.
To evaluate the growth capacity and some chemical characteristics of two Crotalaria species, C. incana and C. pallida, used as green manure, we conducted a field experiment at Osaka, Japan. Both Crotalaria species exhibited vigorous vegetative growth, and leaf area was expanded in C. pallida and branching was promoted in C. incan. Top dry weight and nitrogen content of C. pallida were twice as high as those of C. incana at 87 and 120 days after transplanting (DAT), and the lower values in C. incana were attributed to drastic defoliation of lower leaves due to earlier anthesis from mid-July. Several indicators for rapid decomposition of the plants used as green manure, such as C/N ratio, lignin (L) content and L/N ratio at 56, 87 and 120 DAT, were significantly higher in C. pallida than in C. incana. However, these values might not be critical for nitrogen mineralization after incorporation of the materials into soil. To evaluate the qualitative traits of the two species as green manures, the materials were mixed with soil at a rate of 20 g fresh weight per pot, and seeds of wheat were sown at 10 and 30 days after mixing the green manure (DAM). The growth and nitrogen uptake of wheat grown on the soil mixed with C. pallida were inferior to those of wheat grown on the soil mixed with C. incana on both sowing dates, and the difference between the effectiveness of the two species as green manure was larger in the wheat sown on 10 DAM than on 30 DAM. The possible increase in nitrogen supply and growth inhibition by incorporation of these materials to wheat plants were discussed.
The number and development of spikelets on a panicle directly affect the grain yield. In this study, we examined the differences among various rice cultivars in the number of spikelets per panicle (NSP-1) on the main stems (MS), primary tillers (PT) and secondary tillers (ST), and in the numbers of spikelets on the primary and secondary rachis branches. The difference among cultivars in the responses of these characteristics to the practice of nitrogen-free basal dressing accompanied with sparse planting density (BNo) was also elucidated. The results showed that NSP-1 varied with the tiller position on a plant, and it was highest on MS followed by PT and ST in this order in all cultivars. NSP-1 on all MS, PT and ST also varied with the cultivar, and was larger in the cultivars of the panicle-weight type than in those of the panicle-number type. The difference between MS and ST in NSP-1 was larger in the cultivars of the panicle-weight type than in those of the panicle-number type.NSP-1 was larger in BNo than in the conventional cultivation (CONT) in most cultivars. The difference between BNo and CONT in NSP-1 varied with the tiller position on a plant and with the earliness of the cultivar, but did not clearly vary with the plant type of the cultivar. It was larger in the panicle on ST than on MS or PT, and was larger in the late-maturing cultivars than in the early- and medium-maturing ones. The larger NSP-1 on MS or PT compared with ST, in the cultivars of the panicle-weight type compared with those of the panicle-number type, and in BNo compared with CONT was mainly attributed to the increased number of spikelets on secondary rachis branches.
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