The effects of applied nitrogen (N) doses on crude protein and amylose accumulation in rice grains on primary and secondary rachis branches and their palatability were examined. The crude protein content of rice grains on both primary (PRB) and secondary rachis branches (SRB) increased with the increase in N supply showing a strong negative correlation with palatability. The correlation coefficient between protein content of the grains on PRB and SRB was –0.92 and –0.98, respectively. Although the amylose content also decreased with increasing N supply, the change was not significant on either PRB or SRB. However, it showed a good correlation with palatability; i.e., the correlation coefficient on PRB and SRB was 0.93 and 0.84, respectively. Analysis of protein by SDS-PAGE showed that the contents of protein bodies PB-I and PB-II, were correlated with palatability, but the latter had a higher correlation. The grains on PRB showed a higher palatability than those on SRB due to the difference in the accumulation pattern of proteins and amylose. These results suggest that when breeding for varieties with good palatability, the plants with more grains on PRB should be selected and by maintaining the nitrogen level in the field, we can control protein accumulation and thus can improve the palatability of rice crop.
Transpiration from rice (Oryza sativa L.) panicles can help lower the temperature of the panicle (Tp), which is the susceptive organ for high temperature-induced spikelet sterility (HISS). By increasing the transpiration, the heat damage to the panicle predicted to occur due to global warming may be avoided. To examine the possibility of genetic improvement in transpiration conductance of intact rice panicles (gpI), we measured gpI at the time of flowering in the open field in 21 rice varieties of widely different origins. We observed a difference in gpI among the varieties and three series of experiments, ranging from 0.15 to 0.67 cm s-1. We also estimated its impact on the difference between Tp and air temperature (Ta) (ΔTp,Tp - Ta) using a micrometeorology model, where Ta was given as 28ºC or 35ºC. The varietal range in gpI was estimated to correspond to the range of 2.1ºC in ΔTp under a humid atmospheric condition and the range of 3.5ºC in ΔTp under a dry atmospheric condition. The estimated ΔTp ranges due to varieties may be useful for improving heat avoidance capacity under excessive heat at the critical stage. The sensitivity analysis of ΔTp to ranging gpI suggested that gpI higher than the highest gpI observed in this study may not be effective for additional cooling of Tp. Thus, the target of improvement in gpI against HISS should be set at the level of the existing varieties with the highest gpI.
The relationship between nitrogen efficiency (NE), defined as seed yield per unit nitrogen (N) application, and seed quality was examined in two oilseed rape (Brassica napusL.) varieties at 5 N application levels, 0.6, 3, 6, 12, 15 mmol L-1, N1, N2, N3, N4 and N5, respectively. Seed yield, oil yield and protein content were increased with the increase in N application level, but NE and oil content were decreased, and the fatty acid composition in seed was hardly changed. Analysis of seven fatty acids revealed a slight decrease in the contents of erucic acid and arachidonic acid with the increase in N application level, but no obvious change in the contents of palmitic acid, stearic acid, oleic acid, linoleic acid and linolenic acid. Compared with the low NE variety H29, the seed yield and contents of erucic acid and arachidonic acid in the high NE variety bin270 were more markedly increased with the increase in N application level, and the oil content was hardly changed. The seed yield, oil content and oil yield were higher in the high NE variety than in the low NE variety at all 5 N application levels. There were no significant differences in protein, palmitic acid, stearic acid and oleic acid contents between the varieties at any of the 5 N application levels, but there were slight differences in the linoleic acid and linolenic acid contents between the two varieties. In brief, N application improved oil yield more greatly in the high NE variety than in the low NE variety, but hardly affected the fatty acid composition. Therefore, the seed quality and oil content of oilseed rape may not be decreased by breeding of a high NE variety with a high N absorption efficiency and high N use efficiency.
The F1 plants of crosses between indica andjaponica rice cultivars often have black hulls during ripening, even though both of the parental cultivars have yellow hulls. Complementary genes are suggested to be necessary for the black hull phenotype, and one of them is predicted to be Phr1, which encodes polyphenol oxidase. On the other hand, Bh4, which encodes a tyrosine transporter, is known to cause the black hull phenotype in wild rice species, Oryza rufipogon. However, the relationship between Bh4 and Phr1in the black hull phenotype has not been elucidated. In this study, a genotype analysis of the segregating populations from the cross between an indica cultivar, Habataki, and a japonica cultivar, Arroz da Terra, indicated that only those plants that had both functional genes, Bh4and Phr1, showed the black hull phenotype, suggesting that a complementarity ofBh4and Phr1was necessary for the black hull phenotype.
We verified the effect of high-temperature stress applied to the root on the occurrence of white immature kernels (WIKs) in order to breed rice (Oryza sativa L.) cultivars tolerant to the high temperature during the ripening period. The plants were grown in control and warmed pools after the heading date. The WIK percentages in the warmed pool were higher than those in the control pool. This suggests that high-temperature stress applied to the root increases the occurrence of WIKs. On the other hand, the WIK percentages correlated positively and significantly with the 1000 kernel weight and kernel width, suggesting that rice cultivars with high-temperature tolerance might have a smaller and/or thinner grain.
The aims of this study were to detect plasma-membrane intrinsic protein type 2 (PIP2) genes of soybean (cv. Enrei) and to analyze mRNA levels of these genes under normoxic (control) and hypoxic conditions. A sequence similarity search with cDNA sequences in soybean genome revealed three putative aquaporin genes with high homology to GmPIP2;2. The genes were designated GmPIP2 genes. The mRNA levels in roots of soybean seedlings were measured at 3, 6, 12, and 27 hr after hypoxic stress onset. The mRNA levels of all GmPIP2s showed clear diurnal changes in the control, meanwhile, those under hypoxic conditions were significantly down-regulated even at 3 hr after stress onset. These results suggest that the fourGmPIP2 genes are transcriptionally co-regulated by the diurnal change and oxygen concentration in the surrounding environment, and the transcriptional regulation may be involved in adjustment of water-transport in roots of soybean seedlings.
The suitability of anaerobically-digested manure (ADM) from a biogas plant, as an alternative to chemical fertilizers for rice cultivation was evaluated by a long-term study. At the standard nitrogen (N) application rate (10 g m-2), the aboveground biomass, N uptake, and grain yield in rice plots with ADM application (MF) were not significantly different from those in the plots treated with chemical fertilizer (CF). Split application of ADM improved the apparent N efficiency. The N application rate corresponding to maximum grain yield was approximately 15 g m-2 by a split application, and more N application by using ADM saturated grain yield due to decrease in ripened grain ratio and individual grain weight. On the whole, the soil total-C, total-N and available N in the MF plot were not significantly different from those in the CF plot. The available phosphate (P) levels was lower in the MF plot than in either the CF plot or plot without N application (NF), mainly due to lower content of P in ADM. However, the P level remained much higher than the fatal threshold level for the growth of paddy rice. These findings suggest that under appropriate fertilization conditions, ADM is a valuable organic resource, and can be used continuously as an alternative to chemical fertilization for rice cultivation, without substantial changes in soil C and N fertility.
A narrow-band dual camera system demonstrated a new close-range sensing technique to seasonally track trends in leaf greenness in rice paddies. A weatherproof digital imaging system for the visible red (RED, 620—650 nm) and near infrared band (NIR, 820—900 nm) was positioned 12 m above a 600-m2 rice field. During the 2009 and 2010 paddy rice seasons, the system automatically logged images at 10-min intervals throughout the day. Radiometric corrections for the images utilized solar irradiance sensors and prior calibration to calculate 0900-1500 JST daily-averaged reflectance factors (DARF). The DARF in RED (DARF-RED) and NIR (DARF-NIR) values were transformed to provide a daily-averaged normalized difference vegetation index (DA-NDVI). The DA-NDVI increased more rapidly in the vegetative growth period, and reached an asymptotic plateau earlier than the DARF-NIR. From transplanting to harvest, leaf greenness values (measured by the SPAD index) were measured for the central part of the uppermost leaves of targeted canopies weekly with a chlorophyll meter. We developed a leaf greenness index (LGI), the ratio of DA-NDVI to DARF-NIR, and a simple calculation method for area means to reduce the background effect. The modified area means of LGI followed the seasonal trend in SPAD value well; its pattern was inherently different from the patterns of any of the original three parameters: DARF-RED, DARF-NIR or DA-NDVI. Throughout the paddy seasons in the two years, a regression equation for estimating SPAD values using the LGI, daily solar radiation, the cosine of angle between the view and the meridian directions and the cosine of culmination solar zenith angle performed favorably (R2=0.815). The nitrogen concentration per dry plant hill (g kg-1) had a close relation to the SPAD values estimated using the equation.
The growth and yield potential of soybean and the effects of mulching on desert sand were evaluated in relation to N accumulation in nodules. The experiment was conducted in concrete framed plots filled with sand obtained from the Dzungar desert or the normal field soil in Shihezi, Xinjiang, China. Drip irrigation with or without mulch was adopted for the experimental plots. The mean soil temperature in the sand plot with mulch was the highest among the plots during the early growth stages. The relative ureide-N content in the soil plots varied from 23.2% at the full flowering stage (R2) to 37.6% at the beginning of the maturity stage (R7). The sand plots showed higher values than the soil plots ranging from 48.7% at R2 to 80.5% at R7, indicating active N2 fixation by nodules. Seed yield did not show a significant difference between the soil and the sand plots. It ranged from 394 g m-2 in the soil plot without mulch to 472 g m-2 in the sand plots with mulch. The results suggested the possibility of extending soybean cultivation into marginal areas of deserts, provided that adequate water was available for drip irrigation and there was active nodulation.
Hand-held SPAD meter can be used to evaluate the leaf nitrogen status of potato. For practical use, it is necessary to select a proper compound leaf, a proper leaflet within compound leaf and position of leaflet suitable for measurement. Therefore, field experiments were conducted in northern China in 2009 and 2010. The SPAD values, plant growth, N uptake of potato plants at tuber initiation and tuber bulking stages under different N supply levels, and final tuber yields were examined. The criteria for determining the most suitable leaf, leaflet and position within a leaflet are that the SPAD values show less variation at a given N supply level, and show a more sensitive response to different nitrogen levels. Our results showed that the coefficients of variance of SPAD values ranged from 8.7 to 25.9% with a leaf N concentration range of 2.1 to 3.8 gN 100 g-1 at tuber initiation stage, and 7.2 to 21.6% with leaf N concentration range of 0.96 to 1.26 gN 100 g-1 at the tuber bulking stage. The SPAD values of the 4th compound leaf from apex were more stable and more sensitive to the nitrogen level than those of other leaves, suggesting that the 4th compound leaf is suitable for estimating the leaf N status using a SPAD meter. Within a compound leaf, the SPAD value of the top leaflet was more sensitive than the other leaflets to nitrogen supply, whereas it was less stable, making it difficult to chose the leaflet for measurement. However, the top leaflet emerges and expands much earlier than the side leaflets, and should be better for SPAD value measurement. The SPAD measurements at the top point of the top leaflet of the 4th leaf demonstrated both less variation and higher sensitivity to nitrogen supply. Therefore, we conclude that the top point of the top leaflet of the 4th compound leaf is the best position for potato N status diagnosis using a SPAD meter.
Seeds of Panicum miliaceum, P. sumatrense, Setaria glauca and S.italica were raised in polyvinylchloride (PVC) tubes filled with sandy soil in a greenhouse to determine the effect of pre- and post-heading water deficit on growth and grain yield. Water stress treatment was initiated 25 days after sowing. The grain yield of S. italica and S. glauca decreased 80 and 70%, respectively, under water stress; and that of P. miliaceum and P. sumatrense decreased 36 and 20%, respectively. The reductions were ascribed to smaller number of grains per panicle, smaller number of panicles and lighter total dry weight. The grain yield decreased when water stress was imposed before heading in S. italica andS. glauca, but both before and after heading in P. miliaceum and P. sumatrense. Mild water stress decreased the leaf water potential of all millets. Osmotic adjustment of the leaf could not explain the interspecific difference in drought tolerance. Water stress increased the root growth of S. italica, S. glauca and P. sumatrense at deeper soil layers at heading. At harvest, it also increased root growth at deeper soil layers in S. italica and S. glauca. There was a significant correlation between grain yield and root dry weight among the millets except S. italica. The drought tolerant millet showed greater drought tolerance to water deficit not only at the vegetative stages but also at the reproductive stages than two susceptible millets.
The spikelet number (SPN) is an important wheat yield component decided before anthesis. Our objective was to determine the effect of nitrogen (N) from urea and ammonium sulfate split-applied at different rates before anthesis on the SPN in the recent Egyptian cultivars Sakha93 and Sakha94 and two commonly used cultivars in pots. The response of SPN to applied N from ammonium sulfate was higher than that from urea in all four cultivars used. However, there was no difference in the responses of SPN to absorbed N from the two fertilizers in any of the cultivars. The SPN per applied and absorbed N was the highest in Sakha94 among the four cultivars. These cultivar differences in the SPN were due to the difference in the spike number. The results suggested that the N from ammonium sulfate has a greater effect on SPN than that from urea in recent Egyptian cultivars.