枝梢环剥对荔枝新梢生长和叶片矿质营养的影响

环剥处理中断韧皮部光合产物向下运输及抑制枝梢生长的效应已经明确,但对不同矿质营养运输的影响则有待进一步揭示。研究以妃子笑荔枝为试材,揭示了枝梢环剥处理对新梢生长和叶片矿质营养的影响。结果表明,枝梢环剥处理可强烈抑制枝梢上的新梢发生;环剥17 d后,叶片叶绿素指数明显下降;同时,环剥口上端的叶片不同的矿质营养发生不同的变化。其中对钾和镁影响微弱,而氮、磷、钙、铁、锰、铜、锌等矿质营养含量发生不同程度降低,其中微量元素铁、铜、锰的含量下降较为明显,这表明,中断韧皮部运输也会导致叶片摄取这些矿质元素的减少。     

土壤氮异质性与种间地上竞争对玉米和马铃薯生长的影响

由于不均匀施肥、有机质分解和群体结构复杂化等因素,氮在间作农田土壤中的分布具有异质性。因此,间作作物的生长同时受到种间竞争和异质性氮的影响。然而,人们对作物种间关系(特别是地上竞争)与异质性氮在影响作物生长中有何关系还知之较少。本研究以玉米与马铃薯间作模式为试验对象,在盆栽条件下采用控释性氮肥构建异质性,利用根管分隔去除地下竞争后,通过目标植物法设计地上竞争处理,探讨作物的觅养精确度、生物量生产、功能性状、竞争能力和总相对生产力对氮分布和地上竞争的响应。结果表明:异质氮处理的总相对生产力高于均质氮处理,这可能是因为与无竞争相比,地上竞争提高两作物的觅养精确度。但在地上竞争下异质氮抑制马铃薯的生长,玉米生长得以提高,而在无竞争下异质氮处理提高两作物的生长;这些生长变化在功能性状上得到进一步体现,包括根冠比、根叶比、叶重比和根重比;从竞争能力来看,相对于均质氮处理,异质氮处理促进玉米但降低马铃薯的竞争能力,故马铃薯在均质氮条件下有竞争优势,而玉米则在异质性氮条件下具有竞争优势。总之,地上竞争改变作物对异质性氮的觅养行为,而异质性氮提高作物生长,改变玉米和马铃薯的相对竞争能力,因此地上竞争和氮异质性在调控作物生长过程中存在相互影响,这一发现可增加对间作体系中氮利用特征的认识,也有助于理解农田间作系统中作物生长变化的复杂性。     

用加热四环素治疗柑桔黄龙病芽条的试验初报

从甜橙、蕉柑和化州橙的病树上取具有典型黄龙病症状的芽条,分别用不同温度的1000ppm盐酸四环素溶液处理一定时间。试验结果表明:用44,46,48和50℃处理15min,45℃处理10,20和25min,47℃处理10和20min,49,50和51℃处理10min的病芽条,嫁接于无病红桔实生苗上,经连续3年观察,均未见发病。而用20℃1000ppm盐酸四环素溶液浸20min或20℃清水浸15和20min,以及分别用44,45,46和47℃热水处理15min,则有31.1％～95.1％的植株发病。柑桔芽条用45～48℃的四环素溶液处理10～15min,既保证治疗效果,又有较高的成活率,可在生产上推广应用。     

木本植物诱导发育阶段逆转的研究——桑树茎尖嫁接砧木对嫁接效果的影响

在无菌条件下将桑籽播种至1/2MS无机盐及0.2%凝胶剂(Gelrite)的培养基上,在26℃1000lx、16h/d光照下培养2周后,以激素处理茎切段,转至蛭石培养基,在26℃暗培养10～14天,苗茎围粗达8mm时,以长2cm的切段为钻木.以707桑品种的1～2mm茎尖作接穗,嫁接成功率达75%～80%.     

苹果茎尖培养中无菌繁殖系建立的研究

试验以苹果品种新红星、奥查金、美铃７为试材，对影响无菌繁殖系建立的两个主要因素即污染率和分化率进行了研究。结果表明：在４月下旬，各品种均已展叶４￣５片时接种生长点，污染率较低，成活率较高，且易于生长分化。并发现不同品种间分化难易程度有很大差异，新红星是一个较难分化的品种，通过研究，其较适的组培条件是：改良Ｃ１７＋ＢＡ０．５ｍｇ／Ｌ＋ＩＢＡ０．２ｍｇ／Ｌ＋ＣＨ３００ｍｇ／Ｌ＋蔗糖３０ｇ／Ｌ为起始培养     

干旱对夏玉米根冠生长的影响

利用大型活动式防雨旱棚,人工严格控制不同的土壤含水量,全生育期系统研究了夏玉米根冠生长对水分的响应,结果表明:干旱并不影响夏玉米根系、冠层干物质累积、株高增加、茎(基)粗增大等过程的总趋势。但随胁迫的增强,根、冠干物质累积速率、干物质累积总量降低,根条数变少、株高降低、茎(基)粗变细,但它们并不呈线性相关关系;水分供应量的减少延长了夏玉米的生育周期,随胁迫的增强,根系生物量最大值、最大根条数、冠层最大株高出现的时间延后;根冠比(R／S)随土壤水分的改变而改变;不同水分处理的夏玉米,R／S值影响最小的时期是开花-灌浆盛期,最大的时期是在拔节-抽雄,此阶段充分供水处理H的R／S是严重水分胁迫处理L的125.77％。充分供水的处理则有最大的根冠比(R／S=0.173)。在干旱条件下,协调夏玉米根冠平衡,最大程度发挥根系和地上部叶片的功能,才有利于提高产量。     

不同浓度IBA和NAA对蓝莓组培苗瓶外扦插生根的影响

[目的]探索蓝莓组培苗瓶外扦插生根的适宜条件与技术方法。[方法]以北高丛蓝莓"雷戈西"组培苗为材料,研究不同激素处理对蓝莓组培苗瓶外扦插生根条件的影响。[结果]在吲哚丁酸(IBA)、萘乙酸(NAA)和混合植物生长激素(NAA+IBA)3种不同组合中,IBA生根效果最明显为61.11%,其次为NAA的53.47%,最差的为NAA+IBA的40.87%。[结论]蓝莓组培苗扦插生根用800mg/L的IBA最为适宜。     

Response of aerobic rice growth and grain yield to N fertilizer at two contrasting sites near Beijing,China

In the system of “aerobic rice”, especially adapted aerobic rice varieties are grown under non-flooded conditions in non-puddled and aerobic soils with supplemental irrigation and moderate external inputs. Limited research has been done so far on optimizing nutrient management to produce high yields. In this study, we investigated yield formation and dry matter translocation of aerobic rice cultivar HD297 in response to N application, grown under different irrigation regimes at two sites close to Beijing, North China. At the “experimental farm”, the groundwater table depth was 0.2–1 m; at the “experimental station”, it was deeper than 2 m. Fertilizer-N rates were 0, 75, and 150 kg N ha⁻¹ applied in split dressings according to regional recommendations for lowland rice, with 30% being applied at sowing, 40% at tillering, and 30% at panicle initiation.     

魔芋茎尖组织培养及快速繁殖技术研究

以魔芋茎尖为外植体,进行愈伤组织诱导、芽分化及植株再生的研究。研究结果表明,最佳茎尖剥取材料是无菌试管苗。刚剥离的茎尖需要预培养30d,然后将膨大的茎尖四周给予伤口后再转接到MS 6-BA 0.6 mg/L NAA 0.1 mg/L上进行愈伤组织诱导;芽分化最适培养基是MS 6-BA 2.0 mg/L NAA 0.5 mg/L;切割后的芽在生根培养基1/2 MS NAA 0.1 mg/L上能100%形成完整植株。     

Establishment,survivorship, and growth of yellow birch seedlings after site preparation treatments in large gaps

The occurrence of yellow birch (YB) in the northeastern forests of North America is a source of concern. Several guidelines suggest ways to favor the regeneration of this species, including creating openings from small gaps to large clearcuts, coupled or not with a variety of soil preparation treatments. However, it is not clear if soil preparation treatment favors YB establishment by simply increasing the availability of good seedbed types, or by also altering competition pressure exerted by interfering species during the period of seedling establishment. For this study, large gaps (900 m²) were created in a 70-year old YB dominated forest, to which three treatments differing in soil disturbance intensities were applied (i.e., soil scarification (i) using a rake [raking]; or (ii) by dragging slash out to the edges of the gap [slash drag]; and (iii) limited to the passage of the harvesting equipment [control]). The proportion of seedbed types reportedly most favorable for YB establishment (i.e., mineral-dominated) increased as the severity of the site preparation increased. The opposite was observed for organic-dominated seedbeds. As a result, the stocking of YB seedlings increased with the severity of site preparation. However, YB stocking was deemed sufficient in all gaps to ensure future canopy dominance, even in the control treatment. Although YB seedlings generally achieved greater heights as site preparation intensity increased, it was clear that this did not reflect vigorous growth as, on average, greater heights coincided with greater seedling height–diameter ratios. At the seedbed level, height–diameter ratio was associated with an increase in surrounding competition pressure and an increase in the incidence of stem apical death (SAD), which in turn decreased height differences among seedbed types by the end of the study. At the gap level, this blurred the advantages of site preparation over a laisser-faire strategy. The incidence of SAD was greatest in the slash drag and the rake treatments. Consequently, we cannot say that intense soil scarification is worth the expenses, especially in stands where YB seed sources are abundant.