Field Evaluation of Cocksfoot,Tall Fescue and Phalaris for Dry Marginal Environments of South‐Eastern Australia. 2. Persistence

Perennial grasses provide forage and environmental benefits in the agricultural systems of southern Australia, but persistent cultivars are lacking for the lower rainfall inland margins (<600 mm average annual rainfall). Potential new cultivars of cocksfoot (Dactylis glomerata L.), tall fescue (Festuca arundinacea Schreb. = syn. Lolium arundinaceum (Schreb.) Darbysh.) and phalaris (Phalaris aquatica L.) have been developed in response to this need. These and older cultivars were evaluated for persistence at five sites in south‐eastern Australia from 2009 to 2013. A wide range in rainfall was experienced, but survival was principally reduced by a severe spring–summer–autumn drought in the final year in which all species began to decline in persistence once the spring 2012 to autumn 2013 cumulative climatic moisture deficit became higher than about 700 mm and declined very severely at deficits over 1000 mm. The highly summer‐dormant cocksfoot ssp. hispanica control cultivar Kasbah showed outstanding survival of this event in the cropping zone of southern New South Wales, but not at the drier of two sites with acidic soils in central Victorian where all cocksfoot cultivars showed similar survival. Potential new summer‐active tall fescue cultivars survived well at the higher rainfall Victorian site and under high rainfall in northern NSW. All tall fescue cultivars experienced high mortality during a period of high moisture stress in the spring of the establishment year in southern NSW, but the Mediterranean cultivar Grasslands Flecha MaxP gradually recovered. Differences among phalaris cultivars were not large with new cultivars of North African origin being marginally more persistent at the drier site in southern NSW. Comparisons with results from the Mediterranean Basin are discussed. Although there was no clear evidence of differences in persistence between the new and old cultivars, some of the new cultivars were considered to show potential for commercial release.     

Effects of contrasting seasonal growth patterns on composition and persistence of mixed grass‐legume pastures over 5 years in a semi‐arid Australian cropping environment

Perennial grass‐based pastures are uncommon in phased cropping rotations in south‐eastern Australia, where rainfall often limits production and persistence. The high reliance on pure legume‐based pastures limits overall pasture productivity and has adverse effects on environmental parameters such as weed incursion and ground cover. A field experiment was monitored over 5 years to examine the relative productivity of the temperate perennial grasses, phalaris (Phalaris aquatica) and cocksfoot (Dactylis glomerata) and determine whether contrasting seasonal activity enhances their persistence when grown in mixtures with lucerne (Medicago sativa) and annual legumes. Phalaris swards were shown to increase cumulative aboveground biomass by up to 96% and 32%, and in year 5 reduce annual grass emergence by between sevenfold and threefold compared to annual legume and lucerne/annual legume mixed swards, respectively. Only swards that included phalaris maintained ground cover above 70% in each autumn of the experimental period. Swards based on the highly summer dormant cocksfoot cultivar, Kasbah, were generally less productive over all, despite the cocksfoot showing a high level of persistence and good recovery following drought. Grass‐based swards that included lucerne were observed to produce ~35% greater legume biomass than a sward sown only to annual legumes. Cumulative legume biomass was greatest in lucerne swards in the absence of perennial grasses. The experiment was unable to demonstrate a consistent benefit in production and persistence associated with contrasting seasonal growth patterns. However, mixtures containing a range of functional types were consistently shown to enhance productivity over the duration of the experiment compared to less diverse swards. The potential to substantially increase forage productivity and ground cover, while reducing incursion by annual grass weeds, by including well‐adapted perennial grasses in mixtures with lucerne and annual legumes should be utilized.     

Preliminary evaluation of turfgrass (perennial ryegrass and red fescue) cultivars for resistance to red thread disease using artificial infection

Selection of main cool‐season turfgrasses (perennial ryegrass and red fescue) for resistance to red thread disease caused by Laetisaria fuciformis has not progressed during the last 30 years because of low reproducibility of experiments carried out under natural infection. In this study, evaluation of a set of the turfgrass cultivars, including non‐host fodder grasses as control, was performed in a climatic chamber, a cold house and in the field using three types of artificial inoculum, and correlations between trials were analysed. In general, cultivars of Festuca rubra were more susceptible to the disease but differentiated better than cultivars of Lolium perenne. Significant interactions between cultivars of L. perenne and F. rubra and isolates of L. fuciformis were found. The fungus was also able to colonize leaves of sow thistle and wheat seedlings. In field conditions and in the glass cold‐house Dactylis glomerata was found to be relatively resistant to red thread disease. A possible selection programme is proposed.     

Field Evaluation of Cocksfoot,Tall Fescue and Phalaris for Dry Marginal Environments of South‐Eastern Australia. 1. Establishment and Herbage Production

Newly developed candidate cultivars of cocksfoot (Dactylis glomerata L.), phalaris (Phalaris aquatica L.) and tall fescue (Festuca arundinacea Schreb. = syn. L. arundinaceum (Schreb) Darbysh.) were evaluated over four years for persistence and productivity against current commercial cultivars in small plots at five locations selected for lower and less reliable rainfall and difficult soils (low pH and high Al) in south‐eastern Australia known to be marginally too dry for these grass species. The five locations were ‐ representing summer dominant rainfall, Inverell, in northern New South Wales (NSW); ‐ representing uniform rainfall; Trungley Hall, (medium rainfall), and Beckom (lower rainfall) both in southern NSW; and; representing a winter dominant pattern ‐ Eversley, (higher rainfall), and Bealiba, (lower rainfall), in central Victoria. The objective was to determine if the new candidate cultivars were more likely to persist and to be productive than current commercial cultivars. The study showed that most phalaris and cocksfoot treatments were highly productive in high rainfall years at one or both sites in southern NSW. However, all treatments had become much less productive by the end of the experimental period due to plant loss under hot, dry conditions in the final summer. At Bealiba in central Victoria, cocksfoot was the most productive species with several cocksfoot treatments of both subsp. hispanica and subsp. glomerata still present at the final harvest despite a hot and dry final summer‐autumn. Tall fescue was the most productive species in the two higher rainfall environments (Inverell, Eversley) although most treatments of all species performed well at those sites. Continental tall fescues were more productive on average than Mediterranean tall fescues at the strongly acidic Eversley site. As a result of this work, two of the new cocksfoot candidates (Moroccan Fine and AVH48 Selection) and one of the tall fescue candidates (Summer Active 1) have been licensed for commercial development and release.     

Seasonal Changes in Carbohydrate and Protein Content of Seeded Bermudagrasses and Their Effect on Spring Green‐Up

The widespread use of warm‐season turfgrasses in transition zones of Europe, such as northern Italy, has been hampered by the long dormancy periods. To encourage the conversion from cool‐ to warm‐season grasses, research is needed to identify cultivars that exhibit early spring green‐up. A 2‐year study was conducted at the agricultural experimental farm of Padova University from November 2006 to October 2008 to compare water‐soluble carbohydrate and protein content in stolons of four bermudagrass [Cynodon dactylon (L.) Pers.] cultivars and determine their effect on spring green‐up. Samples of ‘La Paloma’, ‘NuMex Sahara’, ‘Princess 77’ and ‘Yukon’ were collected monthly, and water‐soluble carbohydrates (WSC) and crude protein (CP) content of stolons were measured. Dry weight values of WSC and CP for each cultivar were regressed against days needed to reach 80 % green cover in spring (D80). ‘Yukon’ exhibited the highest rhizome dry weight and WSC content during the winter months and was the fastest to reach 80 % green cover. Conversely, ‘Princess 77’ was the slowest cultivar to green‐up in both years. Regression analysis revealed a stronger relationship between D80 and WSC than between CP content and D80.     

Einfluß von Hauptbestandsbildner (Lolium multiflorum Lam., Lolium X boucheanum Kunth, Lolium perenne L. und Dactylis glomerata L.), Narbendichte, N-Düngung und Zeit auf Ertrag, Energiedichte, P/E-Quotient und Nitratgehalt

The influence of main species (Lolium multiflorum Lam., Lolium X boucheanum Kunth, Lolium perenne L. and Dactylis glomerata L.), sward density, nitrogen and time on yield, energy content, crudeprotein/energy ratio and nitrate content The aim of this investigation was to determine the influence of different rates of nitrogen fertilizer and of varied sward density on yield and chemical composition of some non-perennial (Lolium multiflorum, Lolium X boucheanum) and some perennial species (Lolium perenne, Dactylis glomerata) in a field experiment. Excepted 600 kg N ha^?l - yr^?1 the non-perennial species produced the highest energy yields. At a fertilization level of 400 kg N ha^?1 yr^?1 had sward density an influence on energy yield of Lolium multiflorum. It appeared that almost the energy content of the Lolium species was higher than in Dactylis glomerata. In most cases there were little differences between the Lolium species. There was a positive correlation between the NFEcontent and the content of water soluble carbohydrates and the energy content which was depressed by applying increasing rates of fertilizer. Generally at the lowest rate of nitrogen used (200 kg N ha^?1 yr^?1) there were positive effects on crude protein/energy ratios. The crude protein/energy ratio was higher of Dactylis glomerata than that of the Lolium species. The nitrate content increased to critical values when applying 400 kg N ha^?1 yr^?1. Dactylis glomerata had the highest and Lolium perenne the lowest nitrate content. At high rate of fertilizer, plots with high sward density sometimes had higher nitrate contents than open swards. The results of the experiment indicate that there are differences in quality even between species with high performance. Regarding the quality of grass swards, future attention should be focused on the main species and on sward density.     

Canopy Architecture and Leaf Nitrogen Distribution of Rice (Oryza sativa L.) under Chronic Soil Water Deficit

The development of vertical gradients of specific leaf nitrogen (SLN) in accordance with light gradients within a canopy is important for maximising resource‐use efficiency. In this study, we aimed to clarify the effect of chronic soil water deficit on the SLN gradient in rice. In a series of field experiments, SLN gradients of an indica cultivar and a tropical japonica cultivar were investigated under chronic soil water deficit. As a result, SLN gradient of an indica cultivar tended to be more uniform than that of a tropical japonica cultivar during the recovery period after dry spells under aerobic conditions: an indica cultivar distributed much N in shaded leaves while a japonica cultivar enhanced the SLN in the upper layers. We conclude that vertical gradient of SLN of indica cultivars becomes less optimal for photo‐assimilation under chronic soil water deficit, although they can take‐up sufficient amounts of N. This would be attributable to the rapid increase in tiller number upon rainfall or irrigation and prolonged tillering period for their recovery growth, leading to a more compact canopy architecture. The tillering habit in the current indica irrigated rice cultivars would be associated with the response of SLN gradients to chronic soil water deficit.     

Ecotypic variation of water-soluble carbohydrate concentration and winter hardiness in cocksfoot (Dactylis glomerata L.)

The variation of the water-soluble carbohydrate (WSC) concentration in foliage and stubble and winter hardiness among cocksfoot (Dactylis glomerata L.) ecotypes originated from diverse countries were studied in the field in order to find a breeding material for the improvement of WSC. The total WSC concentration of foliage was found to be highest in Japanese cultivars and lowest in ecotypes from northern Europe in summer and autumn. The variation of fructan concentration in stubble among ecotypes was larger than the variation of mono and disaccharide concentrations in stubble and that of total WSC concentration in foliage in both winters over which this study was conducted. The total WSC and fructan concentrations in the stubble of ecotypes from Spain and southern Europe, derived from the Mediterranean region, were highest in summer. Ecotypes from Japan showed the highest concentration of total WSC in stubble, and were especially high in fructan concentration in autumn. Ecotypes from France, central Europe and central Asia, like Japanese cultivars, also showed a high fructan concentration. The latitude of origin was negatively correlated with WSC concentration and plant vigor in autumn. The altitude of origin was negatively correlated with plant vigor in autumn and positively correlated with fructan concentration in stubble, winter hardiness and snow endurance. Typhula snow blight resistance was related with the amount of the increase in fructan in the plants and with their growth habits in autumn. The fructan concentration of foliage and stubble in autumn was found to be closely related with winter hardiness in cocksfoot ecotypes. A breeding material which has a high WSC concentration in the foliage could not be found among the ecotypes in this study. However, some ecotypes that showed disease resistance, good winter hardiness and plant vigor would be useful as breeding materials for Hokkaido.     

Etiolated growth in relation to energy reserves and winter survival in three temperate grasses

The role of energy reserves in development of winter hardiness was examined in timothy (Phleum pratense L.), orchardgrass (Dactylis glomerata L.) and perennial ryegrass (Lolium perenne L.) through periodically measuring etiolated growth (EG; shoot growth of crown under dark, warm and humid conditions following defoliation) and determining sugar profiles at critical stages of hardening and wintering. Seasonal changes in weight and duration of EG were monitored by sampling once or twice a month from September to the following April. In all species, total etiolated growth (TEG; total shoot production at each sampling time as determined by weekly or biweekly harvests until exhaustion of reserves) increased from September to reach peak levels during the second hardening stage in mid-November. Thereafter, TEG remained high until the following spring in orchardgrass while it declined linearly in timothy, which had the lowest TEG. The decline in TEG was intermediate in perennial ryegrass. Changes in the duration of EG were most marked in orchardgrass, as it required six weeks to produce about 150 mg g^-1 TEG in early November but only one week in March. The results indicated occurrence of dormancy in apical meristems of orchardgrass at the end of the first hardening stage with temperatures above 0 ^°C, which roughly corresponded with the phase of dormancy in woody plants. Dormancy was weak in timothy and largely undetectable in perennial ryegrass, as measured by the EG technique. A positively significant correlation between total nonstructural carbohydrates (TNC) content and TEG was found in all species. Detailed analysis, however, showed that direct estimation of TNC content using TEG was difficult because TEG production per unit TNC was negatively correlated with TNC level, and the amount of TNC unused in early autumn was more than in the rest of the season. Changes in sugar profiles occurred at transition from the first to the second hardening stage with subzero temperatures and varied with wintering strategy of each species. Simple sugar content dramatically declined while fructan content increased in both timothy (cv. ‘Senpoku’) and orchardgrass (cv. ‘Wasemidori’), which were selected at sites covered with snow for more than 120 days. In contrast, a cold tolerant perennial ryegrass cv. `‘éveille’ selected in the Netherlands retained high amounts of simple sugars. The results suggest that EG technique is suitable to monitor physiological status (amount and rate of mobilization of energy reserves, intensity of dormancy and bud development) of plants expressing winter hardiness. This revised version was published online in July 2006 with corrections to the Cover Date.     

Temperature Before Cold Acclimation Affects Cold Tolerance and Photoacclimation in Timothy (Phleum pratense L.), Perennial Ryegrass (Lolium perenne L.) and Red Clover (Trifolium pratense L.)

The expected temperature rise in late summer/early autumn can change the conditions for acclimation and affect the winter survival of perennial crops. This study examined the effect of the temperature just before the onset of cold acclimation (pre‐acclimation) on freezing tolerance of timothy (Phleum pratense L.), perennial ryegrass (Lolium perenne L.) and red clover (Trifolium pratense L.) populations (both cultivars and breeding populations) adapted to either northern or southern parts of Norway. Using phytotron experiments, we studied whether increasing pre‐acclimation temperature delays growth cessation, affects photoacclimation and reduces freezing tolerance. Furthermore, we assessed whether these effects were related to the latitudinal adaptation of the plant material. The results showed that a rise in pre‐acclimation temperature decreased both cold acclimation capacity and photoacclimation in these species. This affected the freezing tolerance, which was reduced significantly more in northern‐adapted population of timothy and perennial ryegrass compared with southern‐adapted populations. Red clover was less affected by temperature changes than the grasses.     

Summer Dormancy in Phalaris aquatica L., the Influence of Season of Sowing and Summer Moisture Regime on Two Contrasting Cultivars

A series of trials to increase understanding of the summer dormancy trait in Phalaris aquatica was conducted. Autumn‐sown and younger, spring‐sown plants of two cultivars (cvv), known to contrast in expression of summer dormancy, were established and then tested over the following summer under three moisture regimes: long drought; drought + mid‐summer storm; or full irrigation. The autumn‐sown plants of cv. Atlas PG expressed substantial but incomplete summer dormancy under all moisture regimes and exhibited the characteristic responses including significant growth reduction and herbage senescence. The summer‐dormant cv. Atlas PG used 31 mm less soil water over the summer and also began to rehydrate its leaf bases from conserved soil water before the drought broke. The non‐dormant cv. Australian grew whenever moisture was applied and also responded to the mid‐summer storm with a decline in dehydrin expression in leaf bases, whereas no decline occurred in Atlas PG, presumably because it remained dormant. The irrigated, younger, spring‐sown swards of cv. Atlas PG had restrained growth and produced only about 37 % of the herbage of cv. Australian. Drought reduced activity and growth of young plants of both cultivars but while Australian regrew in response to the storm, cv. Atlas PG, grew much less (59 % of Australian) indicating that dormancy, although only partially expressed after spring sowing, was reinforced by summer drought. Australian used more soil water over summer than Atlas PG, and it is suggested that this is why cv Australian is limited to the higher rainfall zones of south‐eastern Australia, particularly where soil water holding capacity is limited.     

水分胁迫对水稻叶片气孔频率,气孔导度及脱落酸含量的影响

试验结果表明，在水分胁迫条件下，水稻新生叶片的气孔频率增大，气孔频率最大值的出现推迟；土壤水分充足（对照）或水分胁迫３天的处理在叶片上有两个气孔频率的高峰，水分胁迫５天的处理仅有一个；随着水分胁迫的加重，保卫细胞长度变短，但叶片顶部和基部保卫细胞长度变化较小，中部的变化较大；水分胁迫后，气孔导度变小，复水后迅速上升，上升的速度因品种不同而有较大差异；在较高叶片水势下，品种盐粳２号叶片的脱落酸（ＡＢ     

Successful hybridization between Lolium and Dactylis

In order to test crossability of Lolium and Dactylis, a total of 4126 florets of six different varieties and ploidy levels of Lolium multiflorum Lam. and L. perenne L. were pollinated using a blend of pollen from two cultivars and three ecotypes of Dactylis glomerata L. Additionally, reciprocal pollinations were carried out on 363 florets of two D. glomerata cultivars with pollen of L. multiflorum. Both pre- and post-zygotic cross barriers were strong. Auxin application was effective in overcoming post-zygotic barriers. One viable hybrid plant arose from 16 embryos. The hybrid between L. multiflorum and D. glomerata showed characteristics of both parents. The symmetric character of the hybrid was confirmed by genomic in situ hybridization. Backcross pollinations with pollen of both parents yielded two plants from five embryos with L. multiflorum only. Both the production of allopolyploid hybrids having characters of both species and the transfer of useful characters of D. glomerata into L. multiflorum should be possible.     

不同物候型茶树内源GA3和ABA的变化及其对腋芽萌发调控的影响

运用酶联免疫吸附分析法(Enzyme Linked Immunity Absorb Assay, ELISA), 研究5个不同物候型茶树栽培品种在2003年3月至2006年3月生育周期及春季腋芽萌发前后茶梢叶片内源GA₃(gibberellic acid)、ABA(abscisic acid)的动态变化。结果表明, 在2003年3月至2006年3月期间, 各品种成熟叶片GA₃的含量在各年度均随着茶树生长呈现“快速降低—略有上升—下降—快速升高”两度上升、两度下降的变化趋势, GA₃含量第一次上升的时间呈早生种早、晚生种迟的趋势; ABA最低值出现的时间呈早生种早、晚生种迟的趋势。5个供试品种成熟叶片GA₃的年平均含量总体为早生种高于中生种, 中生种高于晚生种。冬季茶树休眠期间, 成熟叶片GA₃的含量处于整个生长周期的最低点, ABA的含量处于整个生长周期的最高点。11月至翌年1月, GA₃的平均含量和GA₃ /ABA值与其越冬芽的萌发期呈显著相关。春季茶树腋芽萌发进程中, 嫩梢GA₃的含量总体高于成熟叶片, ABA的含量总体低于成熟叶片。     

The effects of cis-trans ABA on embryo germination and seed dormancy in wheat

Pre-harvest sprouting of wheat grain can cause economic losses especially in cultivars with low levels of seed dormancy. The aim of this study was to determine genotype differences in embryo sensitivity to germination in response to exogenous (+/–) cis-trans ABA treatments at different concentrations. Six white and four red seed-colored bread wheat genotypes that differed in dormancy were grown in a field near Swift Current, Saskatchewan in 2000 as a randomized complete block design with four replicates. The seed samples from this experiment were germinated in a controlled environment at 20 °C without light. The exogenous ABA treatments were 0 μM – whole seed (control), 0 μM-embryos, 25 μM – embryos and 50 μM – embryos. The ABA experiment was a factorial design with four randomized complete blocks with four ABA treatments in all combinations with the ten genotypes. A weighted (by day) germination index (WGI) was calculated for each genotype in each ABA treatment. Genotypes differed in response to ABA. The genotypes, ABA concentration and genotype by ABA concentration interaction effects were significant (p ≤ 0.05). Excised embryos showed significantly decreased dormancy in most of the experimental genotypes. The addition of exogenous ABA enhanced embryo dormancy of most genotypes. This revised version was published online in August 2006 with corrections to the Cover Date.     

Old and New Cultivars of Soya Bean (Glycine max L.) Subjected to Soil Drying Differ in Abscisic Acid Accumulation,Water Relations Characteristics and Yield

Two old (Huangsedadou and Longxixiaohuangpi (LX)) and two new (Jindou 19 (JD) and Zhonghuang 30 (ZH)) soya bean (Glycine max (L.) Merr.) cultivars were used to investigate the influence of soil drying on the abscisic acid (ABA) accumulation in leaves, stomatal conductance (g_s), leaf water relations, osmotic adjustment (OA), leaf desiccation tolerance, yield and yield components. The greater ABA accumulation was induced by soil drying, which also inducing g_s decreased at higher soil water contents (SWC) and leaf relative water content (RWC) significantly decreased at lower SWC in the new soya bean cultivars than in the old soya bean cultivars. The soil water threshold between the value at which stomata began to close and the RWC began to decrease was significantly broader in the new cultivars than in the old cultivars. The new cultivars had significantly higher OA and lower lethal leaf water potential than old cultivars when the soil dried. The old cultivars had greater biomass, but lower grain yield than the new cultivars in well‐watered, moderate stress and severe stress conditions. Thus with soil drying, the new soya bean cultivars demonstrated greater adaptation to drought by inducing greater ABA accumulation, stomatal closure at higher SWC, enhanced OA and better water relations, associated with increased leaf desiccation tolerance, greater water use efficiency and higher yield.     

15%石灰氮催芽后巨峰葡萄芽内激素以及有机物质变化研究

用石灰氮对巨峰葡萄(Kyoho grapevine)进行催芽试验,对休眠解除过程中芽体内源激素和有机物质含量以及淀粉酶活性的变化进行了测定。结果表明:随着ABA含量降低IAA含量升高,冬芽逐渐解除休眠而最终萌发;在药剂处理后淀粉酶活性加强,淀粉降解为可溶性糖供的速度加快,蛋白质含量则先下降后升高,最后诱导大部分的芽都能萌发。该试验进一步证明了GA3、ZRI、AA和ABA含量可能是引起巨峰葡萄休眠的关键原因,而ABA含量水平则应该是引起巨峰葡萄冬芽休眠的最关键因素。ABA含量低则有利于冬芽解除休眠。     

水分胁迫对不同抗旱性小麦品种芽根生长过程中IAA、ABA含量的影响

用30%的PEG-6000模拟干旱条件, 对抗旱性强的北农2号和抗旱性弱的921842萌发期的小麦 幼苗根系进行水分胁迫处理, 分别在处理后0、 3、 8、 20、 32、 45h测定了IAA、 ABA 含量及芽、 主胚根的长度、 含水量。 结果发现： 水分胁迫引起两个品种根、 芽中ABA含 量大量增加, 抗旱性强的北农2号ABA反应较抗旱性弱的921842快。     

外源ABA和6-BA对不同持绿型小麦旗叶衰老的影响及其生理机制

为深入认识植物激素在小麦抗氧化和调控衰老中的作用机制,以持绿品种汶农6号和非持绿品种济麦20为材料,在盛花期后喷施脱落酸(ABA)和6-苄基腺嘌呤(6-BA),考察外源激素对旗叶衰老过程中生理生化指标动态变化以及籽粒产量的影响,并探讨了激素与衰老的关系。结果表明,汶农6号旗叶的超氧化物歧化酶(SOD)和过氧化物酶(POD)活性、叶绿素含量及籽粒千粒重和产量均大于济麦20,且丙二醛(MDA)含量低于济麦20,表明持绿型品种抗氧化能力强,衰老进程较慢,进而获得较高产量。外源ABA和6-BA处理显著提高花后7~28 d旗叶叶绿素含量,提高花后21~35 d可溶性蛋白含量,显著降低花后28~35 d旗叶MDA含量。外源ABA降低两品种旗叶玉米素(ZR)含量,但提高生长素(IAA)和赤霉素(GA)含量,降低了其在花后28~35 d的ABA含量。6-BA处理提高旗叶ZR含量及花后7~14 d IAA含量,降低济麦20花后21~35 d旗叶ABA含量。外源ABA显著提高汶农6号花后7~21 d旗叶SOD活性,喷施ABA对汶农6号旗叶POD和过氧化氢酶(CAT)活性影响没有显著性影响,但显著提高了济麦20花后7~28 d POD活性,喷施6-BA提高了两品种7~28 d SOD、POD和CAT活性。总之,ABA和6-BA处理改变了旗叶内源激素水平,提高抗氧化酶活性,降低MDA含量,延缓旗叶衰老,从而提高了籽粒产量。     

Characterization of a green non‐dormant sunflower (Helianthus annuus) mutant NDG

A sunflower (Helianthus annuus L.) mutant was observed in the progeny of a cross between the sunflower cultivar ‘HA 89’ and an amphiploid of a Helianthus divaricatus L. × P21 cross that exhibited loss of dormancy induction in the developing embryo. Seeds of this mutant frequently germinate on the head about 40 days after pollination. The cotyledons of this mutant remain green, whereas some other non‐dormant mutants exhibit loss of pigmentation. The objectives of this investigation were to compare levels and activities of abscisic acid (ABA), a plant hormone that induces dormancy in developing embryos, in the non‐dormant green mutant (NDG) and ‘HA 89’ from which NDG was derived. Immunoassays showed that abscisic acid was present in NDG and the levels were not significantly different from those in ‘HA 89’. Exposure of excised NDG mutant embryos to 40 μm abscisic acid failed to prevent germination, suggesting that non‐dormancy could result from impairment in ABA receptors or from a defect in other proteins participating in the subsequent signalling pathway that normally induces dormancy.