α-Amylase Activity and Soluble Sugar Supply from Endosperm in Relation to Varietal Differences in Seedling Establishment under Low-Temperature Conditions in Rice (Oryza sativa L.)

Abstract

We examined 𰂱-amylase(EC 3.2.1.1) activity in endosperm in 6 varieties of rice (Oryza sativa L.), which showed different seedling establishment traits in field experiments, using seedlings grown in sterilized agar-bed at 16ºC. At the coleoptile elongation stage and the first leaf elongation stage, there were significant differences in 𰂱-amylase activity among the varieties investigated. However, the varietal difference in 𰂱-amylase activity at the coleoptile elongation stage did not correspond with that in coleoptile growth. Maltose, the immediate product of 𰂱 -amylase activity, accumulated in the endosperm at the coleoptile elongation stage in a greater amount in Fukuhibiki, which has a poor seedling establishment trait, than in Arroz da Terra, which has a superior seedling establishment trait. The concentration of glucose detected in the exudate from the endosperm adjacent to the scutellum at the coleoptile elongation stage was also higher in Fukuhibiki than in Arroz da Terra. The results obtained in sterileagar-bed conditions clearly demonstrated that neither deficiency in 𰂱-amylase activity nor glucose production in the endosperm were responsible for coleoptile growth retardation at 16ºC. Therefore, neither 𰂱-amylase activity nor sugar supply from the endosperm were responsible for the varietal differences seen in the rate of seedling establishment in paddy fields at around 16ºC.     

Analysis on Factors Affecting Seedling Establishment in Rice

Elongations of coleoptile and mesocotyl are related directly to rice seedling establishment in soil and height of plant is related to lodging in rice production.Twelve typical rice cultivars with different lengths of coleoptile and mesocotyl(long,medium and short)were selected by screening the lengths of coleoptile and mesocotyl in 1500 accessions.The seedling establishments of these typical cultivars were compared under the combinations of different sowing depths and flooding durations,and two semi-dwarf varieties(G140,Zhong 96-21)with good seedling establishments and optimum mesocotyl lengths were found.The length of mesocotyl was completely fitted negative binomial distribution and the length of coleoptile was nearly fitted lognormal distribution. Analysis of the relationships among mesocotyl,coleoptile,seeding depth,flooding duration,and their interactions to seedling establishment percentage showed that there existed significant relations among mesocotyl,coleoptile,mesocotyl×coleoptile, seeding depth,flooding duration and mesocotyl×sowing depth in the experiment for seedling establishment.     

Does Allelopathy Play a Role in Suppression of Mugwort (Artemisia vulgaris) by Alfalfa?

Abstract

Alfalfa suppresses mugwort growth in the field. In the present study, the allelopathic effect of alfalfa on mugwort was examined using the above-ground (AGAB) and under-ground alfalfa biomasses (UGAB), and their water extracts. The sprouting of mugwort rhizomes or seed germination, growth of seedlings and leaf color changes in mugwort seedlings were evaluated in pot experiments. AGAB mixed into soil highly inhibited sprouting of mugwort rhizome fragments and growth of seedlings. The inhibitory effect was increased, and gradual leaf discoloration (yellowing) was observed in response to a higher dose of AGAB. However, UGAB affected neither sprouting of mugwort rhizome fragments nor growth of seedlings. The growth of mugwort seedlings was not significantly affected by water extracts of either AGAB or UGAB applied after emergence. The seed germination and seedling growth were significantly reduced by water extracts of AGAB and UGAB in the petri dishes experiments. These results indicated that the allelopathic effect of alfalfa along with the competitive ability and harvesting regime may play an important role in suppressing mugwort growth.     

小麦种质资源耐深播性评价体系研究

为建立准确、简单易行的种质资源耐深播评价体系,以15份耐深播能力存在不同程度差异的小麦种质为材料,在大田环境下,研究6个播种深度(5 cm、7 cm、9 cm、11 cm、13 cm、15 cm)下小麦出苗率、出苗时间、苗高、地中茎长、胚芽鞘长、胚芽鞘横截面积及初生根长的差异,筛选小麦耐深播评价的最佳播种深度及其密切相...     

水稻出苗顶土动力源研究

在自然条件下,通过设计不同的出苗阻力（覆土深度2 cm、4 cm和6 cm）来测定中胚轴伸长潜力不同的水稻种质的出苗速度、成苗率和芽鞘节及中胚轴的长度,以分析影响水稻种子顶土出苗的动力源。结果表明,水稻种子的出苗动力主要来源于芽鞘节间和中胚轴的伸长。在不同阻力处理条件下,不同种质出苗动力差异较大,其中覆土2 cm的不同种质出苗率相差不明显,与室内发芽率结果比较接近,覆土4 cm和覆土6 cm的两个处理不同种质间出苗率差异明显,长胚轴种质出苗速度快,出苗率高,出苗率与室内发芽率相差不大;而短胚轴种质出苗速度慢,出苗率低,其中春江683的出苗率与室内发芽率相比分别下降了6.5和86.2个百分点。研究表明水稻中胚轴的伸长对覆土较深的种子顶土出苗起到关键作用,长胚轴种质顶土出苗动力来自于芽鞘节与中胚轴的共同作用,出苗动力强;而短胚轴顶土出苗动力主要来源于芽鞘节的伸长,出苗动力较弱。还对通过选育长胚轴直播稻品种解决直播稻易倒伏和出苗差等难题的可能性进行了探讨。     

The Development of Coleoptile Tillers in Relation to Seedling Vigor in Early-Maturing Varieties of Spring Type Wheat

Abstract

Increase in seedling vigor is necessary to improve the yield of early-maturing spring wheat with a limited growth period. The importance of coleoptile tillers in increasing seedling vigor has been suggested. However, most previous studies on the development of coleoptile tillers have been made with only a limited number of varieties and under controlled environmental conditions. In this study, we examined difference in the development of coleoptile tillers among early-maturing varieties of wheat under field conditions. We observed large differences among varieties in the percentage of plants with coleoptile tillers, ranging from 5.6% in Haruyutaka to 60.1% in Bandouwase. The percentage of plants with coleoptile tillers was closely correlated with the number of leaves developed on the main stem. The dry weight of the plants with coleoptile tillers was heavier than that without coleoptile tillers (by 34.8% in Fukuwase komugi). However, in some varieties, the dry weight of the plants with coleoptile tillers was similar to that of plants without coleoptile tillers. The increase in dry weight per plant seemed to be achieved by the production of either a few heavy tillers or many light tillers.     

Factors Relating to Seedling Emergence in Spring Wheat

Abstract

Spring wheat (Triticum aestivum L.) is cultivated in the northern part of Japan. Although the vigorous early growth of spring wheat is desirable, the rapid and uniform emergence of seedlings is reduced by adverse environmental effects, such as excessive soil moisture and low temperature. Analyses of correlations between field emergence day and germination traits under low temperature, after treatment with polyethelene glycol (PEG) and after flooding treatment of 44 varieties from Japan and other countries indicated a general absence of interrelationships. Moreover, there was no significant correlation between field emergence days in trials in 1996 and 1997. Small and large seeds of Haruyutaka harvested in 1994 and 1996 were hand-sown at depths of 3 cm and 10 cm without fertilizer and with standard fertilizer in brown forest soil in a field of the Tokyo University of Agriculture in Hokkaido. The superiority of large seeds over small seeds was demonstrated by the production of more shoot dry matter with sowing at a depth of 3 cm and by the number of emerged plants with sowing at a depth of 10 cm. Although the coefficients of correlation between field emergence day and germination traits of the wheat varieties were low, a sowing method that optimized seedling growth in the field was demonstrated in this experiment.     

Varietal Differences in Biomass Production of Rice Early After Transplanting at Low Temperatures

Abstract

Low temperature decreases biomass production and yield in rice through a number of physiological and morphological changes. We evaluated biomass production in 22 high-yielding genotypes and four commercial japonica cultivars early after transplanting under field conditions for 2 years. The seedlings were transplanted on 30 April or 1 May (early transplanting, ET) and 4 weeks later (late transplanting, LT). The mean air temperature during the 18 days after transplanting in ET was about 4ºC lower than that in LT in both years. The seedling length was greater in high-yielding japonica varieties than in indica genotypes, whereas the seedling character index (SCI), which is the product of plant age in leaf number and the ratio of the seedling weight to its length, was the highest in the indica genotypes. Varietal differences in biomass production were greater in ET than in LT in all rice genotypes. The biomass at 18 days after transplanting was largest in the japonica high-yielding varieties Kusayutaka and Beko-aoba in both ET and LT. The biomass production of the indica genotypes was found to decrease severely after transplanting at low temperatures although the indica genotypes with high SCIs showed faster leaf emergence than the high-yielding japonica varieties. There was a strong positive correlation between the varietal differences in biomass production and shoot length at 18 days after transplanting in ET in both years. Our study suggests that superior shoot elongation in the high-yielding japonica varieties with large biomass allocation to the stems may be advantageous in maintaining biomass productivity at low temperatures.     

Low Temperature Emergence in Crop Plants

Summary

In Canada, seeding of agronomically important crops takes place during the early months of spring when temperatures are well below the optimum. Low temperature reduces the rate and success of germination. This in turn can result in slow asynchronous emergence from the soil and poor stand establishment. As emergence is a function of both germination and early seedling growth, the effect of low temperature on these developmental processes is of great interest. This review examines how low temperature affects germination and early seedling growth in relation to biochemical and molecular processes. As Brassica napus L. cv. Westar, canola, does not exhibit primary or secondary dormancy, it serves as an ideal species in which to study low temperature emergence. First, emergence is reviewed by independent sections covering germination and early seedling growth. Germination is dissected into the three phases of germination. Early seedling growth is broken into sections covering storage reserve mobilization, the expression of gene sets related to developmental stages, and the role of ABA. Next, comparisons between chilling injury in seeds and chilling injury in plants, oxidative stress, and seed priming are discussed. Finally, the current state of experimental evidence and results are used to resynthesize low temperature emergence in Brassica napus with final thoughts on future directions.     

NADPH Oxidases Act as Key Enzyme on Germination and Seedling Growth in Barley (Hordeum vulgare L.)

Reactive oxygen species (ROS) play an important role in seed germination. Although hydrogen peroxide (H₂O₂), a type of ROS, enhances the germination rate of various plant seeds, little is known about the mechanism. NADPH oxidases catalyze the production of superoxide anion (O₂^-) that is one of the ROS and the enzymes regulate plant development. We, therefore, investigated the role of NADPH oxidases in seed germination and seedling growth in barley (Hordeum vulgare L.). The production of O₂^- was observed both in embryo and aleurone layers in barley seeds treated with distilled water (DW). However, it was suppressed in seeds treated with diphenylene iodonium (DPI) chloride, NADPH oxidase inhibitor. Moreover, DPI markedly delayed germination and remarkably suppressed α-amylase activity in barley seeds, indicating the importance of NADPH oxidases in germination of barley seeds. The gene expression and the enzyme activity of NADPH oxidases gradually increased after imbibition, and the enzyme activities were closely correlated with seedling growth after imbibition. Besides, DPI markedly suppressed the seedling growth. These results indicated that NADPH oxidases perform a crucial function in germination and seedling growth in barley. These facts clearly reveal that O₂^- produced by NADPH oxidases after imbibition regulates seed germination and seedling growth in barley.     

Varietal Differences of Flood Tolerance during Germination and Selection of the Tolerant Lines in Common Buckwheat

Abstract

We evaluated the varietal difference in the flood tolerance of germinated seed in 17 Japanese varieties of common buckwheat (Fagopyrum esculentum Moench), including both local varieties and bred varieties or lines of different agroecotypes. Germinated seeds were flooded for 1 day in a growth chamber in June, July and August. The mean rate of seedling emergence from the seeds sown on different dates varied with the variety ranging from 20.4 to 57.4%. The mean emergence rate of summer agroecotypes (29.9%) was significantly lower than that of intermediate and late-summer agroecotypes (42.8 and 40.1%, respectively), and that of local varieties (44.2%) was significantly higher than that of bred varieties or lines (31.2%). These results suggest that inherent variation in flood tolerance was decreased by breeding as a result of a bottleneck effect. The local variety ‘Kitou zairai’, which exhibited a high and stable seedling emergence rate, may be a suitable choice in breeding for flood tolerance during germination. We also attempted to select for flood tolerance under mild selection pressure. Mass selection after four generations increased seedling emergence rate in five of six selected lines (with the exception of ‘Kitawasesoba’) compared with those of unselected populations, although the results varied with the line. These results indicate the possibility of breeding for flood tolerance during the germination period.     

中国北方杂草稻深覆土条件下出苗动力源分析

 以盆栽的方式,采用不同的覆土深度,对中国北方杂草稻的出苗特性进行了研究,分析了杂草稻的出苗动力源。研究结果表明,在中国北方发现的部分杂草稻具有较强的中胚轴伸长特性和芽鞘节间伸长特性。在播种深度较浅时（3 cm）,杂草稻依赖于中胚轴的伸长顶土发芽;当覆土较深时（5 cm）,杂草稻中胚轴伸长特性更加明显,伸长长度加大,同时杂草稻的芽鞘节间也明显伸长,中胚轴和芽鞘节间的共同伸长为深覆土条件下杂草稻的出苗提供了动力基础。     

不同含水量条件下玉米种子包膜对自身吸水过程及幼苗生长发育的影响

在不同水分条件下种子包膜能有效地延迟种子吸水,且不影响出苗和幼苗生长。在盆栽逆境水分条件下,包膜种子能明显提高出苗率,与对照相比能有效地提高幼苗鲜重和干物重,增加叶面积、根系数量、茎基周长以及矮化幼苗以促进苗壮。     

Thermal time approach to predicting seedling emergence dates of red clover,white clover and lucerne in farm fields

A practical method for predicting seedling emergence dates of red and white clovers, and lucerne is proposed. The germination response at seven different constant temperatures ranging from 5 to 35°C was examined. Germination rate, which is a reciprocal of the duration for 50% germination of seeds, was linearly regressed against temperature to calculate the base temperature and thermal constant of seed germination. The calculated values were 3·9°C and 15·8 degree days for red clover, 4·2°C and 13·6 degree days for white clover, and 2·9°C and 17·7 degree days for lucerne. Using the base temperatures, thermal constants, and the daily mean air temperatures at the study site, the seedling emergence dates of the three forage legumes were predicted. At the same time, in an outdoor pot experiment, seeds of these legumes were sown approximately every 3 weeks and seedling emergence dates were determined. The predicted dates of seedling emergence generally fitted the observed dates. Another prediction was attempted using the base temperatures, thermal constants, and normal daily mean air temperatures recorded over more than 30 years in the study site. This prediction showed that the seedlings of the three forage legumes began to emerge at the beginning of April and could continue to emerge until the beginning of November when their non‐dormant seeds were present in the site, and that when the seeds were sown from mid‐November of one year to late March of the next year, the emergence of seedlings was delayed until the beginning of April.     

Calculation of Population Parameters using Richards Function and Application of Indices of Growth and Seed Vigor to Rice Plants

Abstract

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 reproducibility 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.     

Direct seeding as an alternative to transplanting for guayule in southeast Queensland

Guayule (Parthenium argentatum Gray) is a source of high quality rubber and low-allergenic latex. Commercial potential of guayule to produce high value latex products has increased due to the increased incidence of deadly diseases in humans. The objective of this study was to investigate the potential of direct seeding in southeast Queensland as an alternative to establishment by the current high cost transplanting method. Experiments were conducted for 2 years at Gatton, Queensland using physical and chemical seed treatments. NaOCl plus GA₃, osmo-priming with polyethylene glycol, seed pelleting and seed tape planting were tested. Planting depth had a significant influence on seedling emergence. Emergence at 18 mm depth (1.5 seedlings/m) was significantly reduced compared with 10 mm depth (2.9 seedlings/m). Osmo-priming was effective in increasing germination from 36 to 47%. It also improved seedling emergence and vigour. Osmo-priming significantly increased establishment (7.5 seedlings/m) compared with untreated seed (3.3 seedlings/m). NaOCl plus GA₃ did not have a significant influence on germination (38%) or seedling emergence (5.0 seedlings/m) but increased survival at 42 days after planting. Establishment as a percentage of emerged seedlings was high for both osmo-primed and NaOCl plus GA₃ treatments with 89 and 88% respectively, whereas untreated seed had only 70% survival. Osmo-priming also increased vigour as indicated by increased root length (101 mm), shoot height (123 mm), and seedling dry matter (379 mg/seedling) compared with the control (83, 107 mm and 206 mg/seedling, respectively).     

西南麦区小麦品种萌发期抗旱性的综合鉴定及评价

为筛选西南麦区小麦萌发期抗旱性强的品种,用20％ PEG-6000水溶液模拟干旱胁迫,测定41个小麦品种的发芽势、发芽率、发芽指数、苗高、胚芽鞘长度、胚根长、胚根数等性状,并通过加权隶属函数法对供试材料的抗旱性进行综合评价.结果表明,与正常条件相比,20％ PEG-6000胁迫下小麦种子胚根数均降低(西科麦5号和川麦104例外),发芽势、发芽率、发芽指数、苗高、胚芽鞘长度、根长均受到抑制,且不同品种降幅不同.通过加权隶属函数法分析,综合评价值(D值)较大的前五位品种分别是蜀万8号、绵麦228、绵麦37、川麦104和内麦316.利用聚类分析对41个品种的抗旱性进行分类,蜀万8号、绵麦37等5个品种为高度抗旱品种;川麦60、昌麦30等13个品种为抗旱品种;内麦9号、川麦43等10个品种为中等抗旱品种;绵阳26、蜀麦482等8个品种为对水分胁迫敏感品种;川麦55、川麦42等5个品种为对水分胁迫高度敏感品种.除根长外,其他鉴定指标与D值呈极显著正相关,发芽率和发芽指数与D值的相关系数最大(0.87).发芽率和发芽指数可作为小麦萌发期抗旱性快速鉴定的参考指标.强抗旱性品种蜀万8号、绵麦37、绵麦228等可作为西南麦区小麦抗旱育种种质资源.     

甘蓝型油菜秸秆水浸液对水稻萌发和生长的化感作用

为探究油-稻种植制度中甘蓝型油菜秸秆对水稻的影响,研究了不同浓度（0、25%、50%和75%）的3种油菜（沣油737、湘杂油553和中双11）秸秆水浸液处理下,五优308和C两优343两个水稻品种种子萌发和幼苗生长的情况。结果表明,与对照相比,秸秆水浸液总体增加了幼苗的苗高和鲜重,低浓度（25%）下会提高水稻种子的发芽率、发芽指数和幼苗的根长,高浓度（50%和75%）下则起抑制作用。随着浓度增加,湘杂油553的秸秆水浸液提高了五优308幼苗的可溶性蛋白含量,同时降低了其总超氧化物歧化酶（T-SOD）和过氧化物酶（POD）活力;但对C两优343幼苗表现相反的化感作用,显著降低了其可溶性蛋白含量,而提高了其T-SOD和POD活力,25%浓度下显著降低了其丙二醛（MDA）含量。75%浓度的中双11水浸液显著提高了五优308幼苗的MDA含量,并降低了POD活力。25%浓度的沣油737显著降低了C两优343的可溶性蛋白含量而提高了T-SOD和POD活力。综合结果表明,油菜秸秆水浸液浓度越高,对水稻的化感作用越强,且不同油菜品种水浸液对不同水稻品种的化感作用存在差异,本研究中沣油737和五优308...     

Emergence of cuphea seeds treated with different fungicides

Cuphea (Cuphea viscosissima Jacq. × C. lanceolata f. silenoides W.T. Aiton, Lythraceae) is an oilseed crop, with medium-chain fatty acids, being developed for the North Central United States for industrial applications in the manufacture of soaps and detergents. Seed germination and seedling emergence of cuphea is often low when compared to the commercial crops. Identification of seed treatments to optimize seedling emergence and stand establishment for cuphea are important for commercial production. The objective of this study was to determine the effect of several fungicide treatments on pure live seed emergence (PLSE) of cuphea. Pure live seed emergence is defined as total seedling emergence adjusted by the germination of the seed planted. Field experiments were conducted at Prosper, ND and Glyndon, MN, in 2005 and 2006. Previous crop rotations were soybean [Glycine max (L.) Merr.]/hard red spring wheat (Triticum aestivum L.), and soybean/hard red spring wheat/sugarbeet (Beta vulgaris var. saccharifera L.) at Prosper and Glyndon, respectively, for both years. The experimental design was a randomized complete block with six treatments and four replicates. Treatments were: no fungicide applied (check treatment), captan, mefenoxam, fludioxonil + mefenoxam, azoxystrobin, and azoxystrobin + mefenoxam. Plant stand was counted and PLSE was calculated 10 to 15 d after seeding at all locations by counting emerged seedlings in the center two-plot-rows and adjusting PLSE for germination. Greenhouse experiments were conducted with soil treatments (pasteurized and non-pasteurized) and the same fungicide seed treatments as the field experiment. Pure live seed emergence, vigor index, and percent of diseased seedlings were recorded. Plant stand and PLSE were significantly greater for the seed treatments that had mefenoxam at the Glyndon, MN, environments, in which the previous crop was sugarbeet. Soil treatment (pasteurization) increased PLSE and vigor index. All fungicide seed treatments improved PLSE and vigor index and reduced damping-off compared to the untreated check. Results suggest that seed treatments including mefenoxam would be beneficial for commercial cuphea production.     

多效唑对水稻的生物效应及其应用

 多效唑(Multi-Effect Triazole,MET)是一种新型植物生长延缓物质,对水稻(Oryza sativa L.)生长有明显的控制作用,主要表现于减缓稻苗生长速度和抑制节间伸长;其伴生效应有:促进秧苗分蘖与根系生长,减轻水稻移栽后败苗,增进稻株本田期早发增蘖以及防止水稻成熟期间倒伏。可应用于控制连作晚稻秧苗徒长,调节稻作茬口安排;以及减轻因倒伏引起的产量与品质的下降。多效唑对水稻生长的控制效应受气温、氮素施用量以及土壤水分影响;多效唑具有增强气孔抗阻、降低叶面蒸腾等生理作用,并增强稻苗吲哚乙酸氧化酶活性。