Comparative temporal analyses of the <Emphasis Type="Italic">Pinus sylvestris</Emphasis> L. var. <Emphasis Type="Italic">mongolica litv.</Emphasis> apical bud proteome from dormancy to growth

Bud dormancy in perennial plants adapts to environmental and seasonal changes. Bud dormancy is of ecological interest because it affects forest population growth characteristics and is of economical interest because it impacts wood production levels. To understand Pinus sylvestris L. var. mongolica litv. bud-dormancy and bud-burst mechanisms, we characterized the proteomes of their apical buds at the four critical stages that occur during the dormancy-to-growth transition. Ninety-six proteins with altered expression patterns were identified using NanoLC–ESI-MS/MS. The majority of these proteins (57%) are involved in metabolic and other cellular processes. For 28% of the proteins, a function could not be assigned. However, because their expression levels changed, they may be potential candidate bud development- or dormancy-related proteins. Of the 75 non-redundant bud proteins identified, ascorbate peroxidase, pathogenesis-related protein PR-10, and heat shock proteins dramatically increased during August and November, suggesting that they may involved in the initiation of bud dormancy. Conversely, S-adenosylmethionine synthetase, abscisic acid/stress-induced proteins, superoxide dismutase (SOD), caffeoyl-CoA O-methyltransferase, actin, and type IIIa membrane protein cp-wap13 had greater expression levels during April, suggesting that they may be involved in the initiation of bud dormancy-release. Cell division cycle protein 48 and eukaryotic initiation factors 4A-15 and 4A had greater expression levels during May, suggesting that they may regulate cell proliferate and differentiation in the shoot apical meristem. These observations provide insights into the molecular mechanisms that induce or break bud dormancy.     

河北坝上樟子松人工林径向生长及其对气候因素的响应

利用树木年轮学方法测定了河北坝上地区樟子松逐年树轮宽度和胸高断面积增量,建立了樟子松树轮宽度差值年表并分析其对气候因素的响应以及生态弹性,为河北坝上地区利用樟子松开展退化杨树防护林更新建设的适宜性提供理论参考。研究结果表明,河北坝上地区樟子松树龄在28 a左右,其生长阶段可划分为快速生长期(0—10 a),生长下降期(11—20 a)和生长平稳期(21—28 a);樟子松树轮宽度在1992—2000年期间为快速增长期((4.49±1.15)mm/a),在2001—2010年期间呈现下降趋势((3.62±1.39)mm/a),而在2011—2019年期间樟子松生长呈平稳特征((2.21±0.68)mm/a),约为快速增长期增长速度的一半;樟子松BAI在1992—2000年间一直呈上升趋势((5.09±2.26)cm~2/a),2001—2019年期间呈平稳特征((10.46±0.67)cm~2/a),表现出稳定且持续的生长能力。樟子松差值年表与气候因素的相关性显示：樟子松径向生长主要与上一年生长季末期(9、10月)、休眠期(12月)及当年生长季(7月)平均温度和最高温度呈显著负相关,其中...     

Relative importance of nodal roots and apical buds in the control of branching in Trifolium repens L.

Clonal species are characterised by having a growth form in which roots and shoots originate from the same meristem so that adventitious nodal roots form close to the terminal apical bud of stems. The nature of the relationship between nodal roots and axillary bud growth was investigated in three manipulative experiments on cuttings of a single genotype of Trifolium repens. In the absence of locally positioned nodal roots axillary bud development within the apical bud proceeded normally until it slowed once the subtending leaf had matured to be the second expanded leaf on the stem. Excision of apical tissues indicated that while there was no apical dominance apparent within fully rooted stems and very little in stems with 15 or more unrooted nodes, the outgrowth of the two most distal axillary buds was stimulated by decapitation in stems with intermediate numbers of unrooted nodes. Excision of the basal branches from stems growing without local nodal roots markedly increased the length and/or number of leaves on 14 distally positioned branches. The presence of basal branches therefore prevented the translocation of root-supplied resources (nutrients, water, phytohormones) to the more distally located nodes and this caused the retardation in the outgrowth of their axillary buds. Based on all three experiments we conclude that the primary control of bud outgrowth is exerted by roots via the acropetal transport of root-supplied resources necessary for axillary bud outgrowth and that apical dominance plays a very minor role in the regulation of axillary bud outgrowth in T. repens.     

呼伦贝尔沙地樟子松林净初级生产力对气候变化的响应

以呼伦贝尔沙地樟子松人工林为研究对象,利用树木年轮学和解析木法,推算过去41年樟子松林的生物量和年净初级生产力,并分析年净初级生产力与气温、降水、湿度等气象因子的关系。研究表明：随着林龄的增加,樟子松林生物量变化符合逻辑斯蒂生长方程;樟子松林生物量从1977年的4.83 t/hm²到2017年的167.95 t/hm²。樟子松林净初级生产力年际差异较大,呈先增加后减小、最后趋于稳定的趋势,多年平均净初级生产力为4.08 t hm^-2 a^-1,最高达到6.13 t hm^-2 a^-1,最低为2.63 t hm^-2 a^-1。气候因子与樟子松林净初级生产力关系较为密切,并具有一定的"滞后效应";樟子松林净初级生产力与上一年8月、12月和当年3月的降水量显著相关;净初级生产力与上一年和当年8-9月的月均湿度极显著正相关;净初级生产力与各月温度均呈不同程度的负相关,尤其是上一年和当年的6-9月温度显著影响着净初级生产力。研究表明,樟子松林净初级生产力受温度和降水的综合影响,净初级生产力与气候因子的关系属于温度敏感型,未来该地区持续升温的条件下樟子松林净初级生产力可能会降低。     

Development and Growth Potential of Axillary Buds in Roses as Affected by Bud Age

The effect of axillary bud age on the development and potentialfor growth of the bud into a shoot was studied in roses. Ageof the buds occupying a similar position on the plant variedfrom 'subtending leaf just unfolded' up to 1 year later. Withincreasing age of the axillary bud its dry mass, dry-matterpercentage and number of leaves, including leaf primordia, increased.The apical meristem of the axillary bud remained vegetativeas long as subjected to apical dominance, even for 1 year. The potential for growth of buds was studied either by pruningthe parent shoot above the bud, by grafting the bud or by culturingthe bud in vitro. When the correlative inhibition (i.e. dominationof the apical region over the axillary buds) was released, additionalleaves and eventually a flower formed. The number of additionalleaves decreased with increasing bud age and became more orless constant for axillary buds of shoots beyond the harvestablestage, while the total number of leaves preceding the flowerincreased. An increase in bud age was reflected in a greaternumber of scales, including transitional leaves, and in a greaternumber of non-elongated internodes of the subsequent shoot.Time until bud break slightly decreased with increasing budage; it was long, relatively, for 1 year old buds, when theysprouted attached to the parent shoot. Shoot length, mass andleaf area were not clearly affected by the age of the bud thatdeveloped into the shoot. With increasing bud age the numberof pith cells in the subsequent shoot increased, indicatinga greater potential diameter of the shoot. However, final diameterwas dependent on the assimilate supply after bud break. Axillarybuds obviously need a certain developmental stage to be ableto break. When released from correlative inhibition at an earlierstage, increased leaf initiation occurs before bud break.Copyright1994, 1999 Academic Press Age, axillary bud, cell number, cell size, pith, shoot growth, Rosa hybrida, rose     

长期极端高温胁迫对樟子松幼苗生物量及非结构性碳水化合物的影响

采集东北地区(红花尔基、黑河、漠河)3个地理种群樟子松(Pinus sylvestris var.mongolica)的种子在温室进行育苗和培养,通过连续4年温室持续高温控制培育实验。研究了极端高温(+15℃,+18℃,+21℃)对不同地理种群樟子松幼苗的株高、基径、根冠比、生物量分配及非结构性碳水化合物(NSC)含量的影响,探明樟子松对高温的耐受程度。结果表明:不同地理种群间幼苗的株高、基径、生物量累积存在显著差异,株高、基径、生长速率和总生物量都表现为:黑河(He)(+15℃)红花尔基(Ho)(+18℃)漠河(M)(+21℃);根冠比大小依次为:红花尔基(Ho)(+18℃)黑河(He)(+15℃)漠河(M)(+21℃)。可溶性糖和淀粉百分含量在同种群不同器官,及不同种群相同器官间均有差异。可溶性糖与淀粉在不同种群间均表现为:黑河(He)(+15℃)红花尔基(Ho)(+18℃)漠河(M)(+21℃),可溶性糖与淀粉在不同地理种群的相同器官中均表现为:叶根茎。黑河樟子松种群的幼苗对高温胁迫表现出较强的适应能力,具有比红花尔基和漠河樟子松更强的抗高温胁迫的生理基础,意味着樟子松幼苗可适应升高15℃的高温环境,而升高20℃则对其产生严重胁迫,是东北地区适应未来全球气候变暖的理想樟子松种源。     

Roles for Auxin, Cytokinin, and Strigolactone in Regulating Shoot Branching

Many processes have been described in the control of shoot branching. Apical dominance is defined as the control exerted by the shoot tip on the outgrowth of axillary buds, whereas correlative inhibition includes the suppression of growth by other growing buds or shoots. The level, signaling, and/or flow of the plant hormone auxin in stems and buds is thought to be involved in these processes. In addition, RAMOSUS (RMS) branching genes in pea (Pisum sativum) control the synthesis and perception of a long-distance inhibitory branching signal produced in the stem and roots, a strigolactone or product. Auxin treatment affects the expression of RMS genes, but it is unclear whether the RMS network can regulate branching independently of auxin. Here, we explore whether apical dominance and correlative inhibition show independent or additive effects in rms mutant plants. Bud outgrowth and branch lengths are enhanced in decapitated and stem-girdled rms mutants compared with intact control plants. This may relate to an RMS-independent induction of axillary bud outgrowth by these treatments. Correlative inhibition was also apparent in rms mutant plants, again indicating an RMS-independent component. Treatments giving reductions in RMS1 and RMS5 gene expression, auxin transport, and auxin level in the main stem were not always sufficient to promote bud outgrowth. We suggest that this may relate to a failure to induce the expression of cytokinin biosynthesis genes, which always correlated with bud outgrowth in our treatments. We present a new model that accounts for apical dominance, correlative inhibition, RMS gene action, and auxin and cytokinin and their interactions in controlling the progression of buds through different control points from dormancy to sustained growth.     

樟子松人工林营建对土壤颗粒组成变化的影响

植被恢复是退化生态系统的主要恢复措施,也是人类改善区域生态环境较为重要和直接的活动。目前,针对不同植被恢复方式对干旱半干旱地区土壤理化性质及生物特征开展了大量研究。然而,关于科尔沁沙地樟子松人工林营建对土壤颗粒组成变化的影响却鲜有报道。因此,以辽宁省章古台地区不同生长阶段(包括幼龄林、中龄林、成熟林和过熟林)的20块樟子松人工林样地为研究对象(以临近的7块天然草地为对照),研究了沙地樟子松人工林营建对0—100 cm土层土壤颗粒组成变化的影响。结果表明:沙质草地营建樟子松人工林后,不同土层土壤细颗粒(0.05 mm)含量均呈增加趋势,并且在0—10 cm层增加趋势明显,随土层深度增加土壤细颗粒增加量逐渐降低(除幼龄林外),但樟子松林地土壤颗粒组成仍以砂粒为主,土壤粘粒和粉粒含量极低(仅占5%左右)。随着樟子松人工林林龄的增加,土壤细颗粒变化量在0—10 cm层逐渐升高,而在10—100 cm层并无显著变化趋势。土壤细颗粒含量的变化在10—100 cm层与土壤含水量呈显著正相关,在0—10、20—40 cm和80—100 cm层与土壤全钾极显著负相关,在20—60 cm层与土壤有机碳呈显著正相关,在10—40 cm和80—100 cm层分别与土壤全磷呈显著正相关和负相关。综上所述,樟子松人工林营建可有效提高土壤细颗粒含量且在土壤表层效果明显,但短期内并不会使土壤颗粒组成发生显著变化,樟子松林改善土壤颗粒组成的同时也会使其他土壤因子发生相应的变化。     

Strigolactone Acts Downstream of Auxin to Regulate Bud Outgrowth in Pea and Arabidopsis

During the last century, two key hypotheses have been proposed to explain apical dominance in plants: auxin promotes the production of a second messenger that moves up into buds to repress their outgrowth, and auxin saturation in the stem inhibits auxin transport from buds, thereby inhibiting bud outgrowth. The recent discovery of strigolactone as the novel shoot-branching inhibitor allowed us to test its mode of action in relation to these hypotheses. We found that exogenously applied strigolactone inhibited bud outgrowth in pea (Pisum sativum) even when auxin was depleted after decapitation. We also found that strigolactone application reduced branching in Arabidopsis (Arabidopsis thaliana) auxin response mutants, suggesting that auxin may act through strigolactones to facilitate apical dominance. Moreover, strigolactone application to tiny buds of mutant or decapitated pea plants rapidly stopped outgrowth, in contrast to applying N-1-naphthylphthalamic acid (NPA), an auxin transport inhibitor, which significantly slowed growth only after several days. Whereas strigolactone or NPA applied to growing buds reduced bud length, only NPA blocked auxin transport in the bud. Wild-type and strigolactone biosynthesis mutant pea and Arabidopsis shoots were capable of instantly transporting additional amounts of auxin in excess of endogenous levels, contrary to predictions of auxin transport models. These data suggest that strigolactone does not act primarily by affecting auxin transport from buds. Rather, the primary repressor of bud outgrowth appears to be the auxin-dependent production of strigolactones.     

Differences in tree and shrub growth responses to climate change in a boreal forest in China

Global climate change has led to rising temperatures and drought in boreal forests in Northeast China. In some areas, shrubs and trees coexist in high altitude and high latitude areas, and their differences with global warming may lead to significant changes in vegetation composition and distribution. Therefore, we compared the relationships between climate and growth for the most widely distributed dwarf shrub (Pinus pumila) and the two dominant tree species (Larix gmelinii and Pinus sylvestris var. mongolica) in boreal forests in the Daxing’an Mountains, China. A total of 340 tree-ring cores from 172 trees and 64 discs from shrubs were collected from four sites and compared the responses of shrub and tree growth to climate patterns using dendrochronological methods. The shrub and two tree species responded differently to interannual climate variance. The negative effect of growing season temperature was greater on growth of L.gmelinii and P. sylvestrisvar.mongolica than on P. pumila, and the promoting effect of winter and spring precipitation was greatest on P. pumila. Compared with the two tree species, P. pumila had a higher temperature threshold and grew over a shorter growing season. Our findings suggested that L. gmelinii and P. sylvestrisvar.mongolica are more susceptible to global warming than the shrubs that coexist with them. However, P.pumila should be studied from an individual perspective in the future due to the dwarf morphology of shrubs and their complex microenvironment.     

黄土高原樟子松和落叶松与其他树种枯落叶混合分解对土壤的影响

通过采集树木枯落叶与土壤进行室内混合分解培养试验,研究了黄土高原常见的樟子松和落叶松与其他树种枯落叶混合分解对土壤性质的影响及存在的相互作用,从而为不同树木种间关系的探索和该地区人工纯林的混交改造提供科学指导。结果表明:12种枯落叶单一分解均明显提高了土壤脲酶(54%—110%)、脱氢酶(85%—288%)和磷酸酶(81%—301%)活性以及有机质(29%—55%)和碱解N(12%—49%)含量,但对土壤速效P含量和CEC的影响存在较大差异。综合而言,樟子松分别与白桦、刺槐、白榆、柠条和落叶松枯落叶混合分解在对土壤性质的影响中存在相互促进作用,而分别与小叶杨、沙棘、紫穗槐、侧柏和辽东栎枯落叶混合分解在对土壤性质的影响中存在相互抑制作用;落叶松分别与刺槐、白桦、小叶杨和紫穗槐枯落叶混合分解在对土壤性质的影响中存在相互促进作用,而分别与柠条、侧柏、辽东栎、沙棘、油松和白榆枯落叶混合分解在对土壤性质的影响中存在相互抑制作用。     

珍稀濒危植物长白松(Pinus sylvestris var. sylvestriformis)天然种群生存压力

为了揭示珍稀濒危植物长白松（Pinus sylvestris var. sylvestriformis）天然种群生存压力状况,在全面调查长白山国家级自然保护区长白松分布的基础上,基于邻体干扰模型,引入树高、冠幅、方位等因子,提出3种生存压力指数：个体生存压力指数、种群生存压力指数和群落生存压力指数,分析天然长白松所处6种群落类型中的生存压力。结果表明：长白松承受群落生存压力（PI）从大到小依次为：白桦-臭冷杉群落（PI=21.532）、红松-长白松群落（PI=14.185）、白桦群落（PI=13.262）、臭冷杉-长白松群落（PI=8.752）、长白落叶松-鱼鳞云杉群落（PI=7.780）和蒙古栎群落（PI=5.440）。多重比较单向方差分析表明,6种群落类型中长白松生存压力总体上差异明显,白桦-臭冷杉群落中长白松生存压力最大,显著高于其他5种群落;竞争树种主要为长白落叶松、红松、长白松、山杨和白桦,这5个树种生存压力大小占群落生存压力的87%;红松-长白松群落和白桦群落中长白松生存压力无明显差异,但显著高于臭冷杉-长白松群落、长白落叶松-鱼鳞云杉群落和蒙古栎群落;臭冷杉-长白松群落、长白落叶松-鱼鳞云杉群落和蒙古栎群落中长白松生存压力相对较小,彼此无明显差异。长白松生存压力与其所处植物群落演替阶段及其龄级结构有关。目前,保护区采取严格保护和管理方式不完全有利于长白松种群的稳定发展。根据长白松种群所处的植物群落生境特点、种群生存压力状况并结合种群年龄结构特征,针对不同群落类型提出相应抚育措施建议以期为长白松天然种群的保护提供参考。     

CnFL,a FLORICAULA/LEAFY homolog in Chrysanthemum nankingense is dramatically upregulated in induced shoot apical meristems

A FLORICOULA/LEAFY (FLO/LFY) homolog CnFL gene was isolated from the flower bud of a short-day Chrysanthemum nankingense plant during the flowering induction period. The sequence of CnFL contained a 1236 bp open reading frame that encoded a putative protein of 412 amino acids, which shared 68.67% homology with FLO and 60.23% homology with LFY. The spatial expression patterns of CnFL were analyzed using quantitative real-time PCR in different tissues and the apical meristem during short-day flowering induction. The results indicated that CnFL was highly expressed in the flower buds while its expression was also detected in the stems, young leaves, and vegetative apical meristem. During the period of flowering induction, CnFL expression increased remarkably and reached its highest levels after 15 days of induction. The expression of CnFL in the apical shoot after short-day flowering induction indicates that CnFL regulation is controlled primarily by photoperiodicity.     

Axillary Bud Inhibition Induced by Young Leaves or Bract in Euphorbia pulcherrima Willd

In plants held under long days in the vegetative stage, youngexpanding leaves of poinsettia (Euphorbia pulcherrima Willd.‘Brilliant Diamond’) are the main source of axillarybud inhibition, while the apical bud, which includes the meristem,primordial leaves and small unfolded leaves, is a secondaryinhibition source. Removal of these expanding leaves resultedin rapid release and growth of axillary buds. Decapitation ofthe apical bud resulted in delayed axillary bud release. Inreproductive plants kept in short days, the pigmented bractsare the primary source of axillary bud inhibition and the cyathiaare the secondary source. Applications of NAA —substitutedfor both young leaves and bract inhibition — maintainedapical dominance. The concentration of endogenous auxin washighest in the apical bud. However, when calculated on wholeorgan basis the auxin level was greater in young developingvegetative leaves and in reproductive bracts than in the apicalbud. Euphorbia pulcherrima Willd, apical bud, apical dominance, auxin, correlative inhibition, cyathia, poinsettia, IAA, NAA     

Foliar-applied Dormex™ or thiourea-enhanced proline and biogenic amine contents and hastened breaking bud dormancy in “Ain Shemer” apple trees

The role of hydrogen cyanamide (Dormex?) or thiourea in the acceleration of dormancy breaking in buds of “Ain Shemer” apple (Malus sylvestris, Mill.) trees, and their effects on metabolic changes in the contents of proline and biogenic amines (BAs; tyramine, tryptamine, histamine, methylbutylamine and serotonin) in buds during bud break were assessed. The efficiency of bud break by these compounds was noticed to varying degrees. Breaking bud dormancy was correlated with the early date of bud break, the short duration of flowering, the high percentages of bud break and fruit set, and the high contents of proline and BAs. This finding was positively reflected in the tree’s yield. Dormex? was found to be more effective than thiourea; therefore, we recommend using Dormex? for early bud break, short period of flowering and high percentages of bud break and fruit set by regulating the contents of proline and BAs in buds.     

Expression of a ribosomal protein gene in axillary buds of pea seedlings

Axillary buds of intact pea seedlings (Pisum sativum L. cv Alaska) do not grow and are said to be dormant. Decapitation of the terminal bud promotes the growth of these axillary buds, which then develop in the same manner as terminal buds. We previously showed that unique sets of proteins are expressed in dormant and growing buds. Here we describe the cloning, sequencing, and expression of a cDNA clone (pGB8) that is homologous to ribosomal protein L27 from rat. RNA corresponding to this clone increases 13-fold 3 h after decapitation, reaches a maximum enhancement of about 35-fold after 12 h, and persists at slightly reduced levels at later times. Terminal buds, root apices, and elongating internodes also contain pGB8 mRNA but fully expanded leaflets and fully elongated internodes do not. In situ hybridization analysis demonstrates that pGB8 mRNA increases in all parts of the bud within 1 h of decapitation. Under appropriate conditions, growing buds can be made to stop growing and become dormant; these buds subsequently can grow again. Therefore, buds have the capacity to undergo multiple cycles of growth and dormancy. RNA gel blots show that pGB8 expression is reduced to dormancy levels as soon as buds stop growing. However, in situ hybridization experiments show that pGB8 expression continues at growing-bud levels in the apical meristem for 2 d after it is reduced in the rest of the bud. When cultured stems containing buds are treated with indoleacetic acid at concentrations ≥10 μm, bud growth and expression of pGB8 in the buds are inhibited.     

寒温带针叶林优势树种倒木分解真菌群落多样性及功能差异

为了揭示寒温带针叶林不同树种倒木分解中真菌群落的分布格局,探讨影响倒木真菌群落分布的养分驱动因子。采用Illumina MiSeq高通量测序技术和R语言等分析方法对微生物多样性数据进行信息挖掘,解析白桦(Betula platyphylla Suk.)、兴安落叶松(Larix gmelinii(Rupr.)Kuzen)、樟子松(Pinus sylvestris var. mongolica Litv.)倒木分解初期真菌群落的多样性及功能差异。研究发现,寒温带针叶林中白桦、樟子松倒木优势菌群为Basidiomycota(担子菌门)、Trichaptum(附毛菌属),兴安落叶松倒木优势菌群为Ascomycota(子囊菌门)、Acidea菌属。多样性分析表明,不同树种倒木真菌群落的Alpha多样性由高到低依次为兴安落叶松、白桦、樟子松,树种的差异极显著的改变了操作分类单元(OTU)、属水平上倒木真菌群落的Beta多样性。菌群生态分析表明,腐生型是3种倒木上优势真菌的主要生态类型,木质腐生为白桦、樟子松倒木上真菌的主要生活方式,土壤腐生为兴安落叶松真菌类群的主要生活方式。养分关联分析表明,pH、全碳(TC)、全氮(TN)、碳氮比(C/N)、半纤维素、木质素等养分指标在3种倒木间存在显著性差异,其中含水率(MC)、TC、TN、纤维素、半纤维素是影响倒木优势真菌群落分布的主要养分因素。不同树种对倒木真菌群落的富集具有差异性,这种差异带来的微生物多样性及功能变化对寒温带森林生态系统的物质循环具有重要的科学意义。     

A Developmental Pattern of Flowering in Colored <Emphasis Type="Italic">Zantedeschia</Emphasis> spp.: Effects of Bud Position and Gibberellin

The restricted flowering of colored cultivars ofZantedeschia is a consequence of developmental constraints imposed by apical dominance of the primary bud on secondary buds in the tuber, and by the sympodial growth of individual shoots. GA₃ enhances flowering inZantedeschia by increasing the number of flowering shoots per tuber and inflorescences per shoot. The effects of gibberellin on the pattern of flowering and on the developmental fate of differentiated inflorescences along the tuber axis and individual shoot axes were studied in GA₃ and Uniconazole-treated tubers. Inflorescence primordia and fully developed (emerged) floral stems produced during tuber storage and the plant growth period were recorded. Days to flowering, percent of flowering shoots and floral stem length decreased basipetally along the shoot and tuber axes. GA₃ prolonged the flowering period and increased both the number of flowering shoots per tuber and the differentiated inflorescences per shoot. Activated buds were GA₃ responsive regardless of meristem size or age. Uniconazole did not inhibit inflorescence differentiation but inhibited floral stem elongation. The results suggest that GA₃ has a dual action in the flowering process: induction of inflorescence differentiation and promotion of floral stem elongation. The flowering pattern could be a result of a gradient in the distribution of endogenous factors involved in inflorescence differentialtion (possibly GAs) and in floral stem growth. This gradient along the tuber and shoot axes is probably controlled by apical dominance of the primary bud. Online publication: 7 April 2005     

Dormancy and spring development of lateral buds in mulberry (Morus alba)

Patterns of spring development of lateral buds of mulberry (Morus alba L. cv. Shin-ichinose) coppice shoots on 11-year-old low-pruned stumps varied in response to girdling, pruning and arching. The erect controls showed a weak acrotonic (apex-favoring) growth habit, in which the majority of the buds, including the basal ones, sprouted and elongated in mid- and late April, and hence there was a prolonged imposition of dominance on the upper laterals in mid- and late May. In contrast, early spring girdling or pruning enhanced the activity of the upper buds of the proximal (lower) halves of the girdled stems or of the pruned stems, resulting in considerable dominance of the laterals from such buds in late April. Arching markedly inhibited buds on the under side of the arched stems, leading to poor shoots. By late April, the buds on the adaxial (upper) side readily grew into new vertical shoots, which dominated over the lateral ones. When studied by a multiple-node-cutting test, increased length of segments of post-dormant mulberry stems was accompanied by decreased bud activity of the segments and by decreased breaking ability of the lower buds within the segments, suggesting the importance of roots in the weak acrotonic habit of the erect stem in spring. By contrast, the acropetal influences of the attached stems can in part affect dominance relationships, perhaps mediated through competition for factors translocated from the roots. Continuous basal applications of abscisic acid inhibited bud break and shoot growth of the postdormant stem segments, but these inhibitory effects could be reversed by applied gibberellic acid A₃ (GA₃). Two phases of lateral bud dormancy in erect mulberry coppice shoots were identified. The first was characterized by a smaller breaking capacity in the upper buds than in the lower ones and hence by a basitonic (base-favoring) gradient in bud growth potential. The second phase corresponded to a restoration of these capabilities in the upper buds and to a change towards a linear gradient in bud growth potential, with disappearance of the dormant condition, in February and March. This gradient change during dormancy release may represent the physiological basis for the weak acrotonic habit of erect mulberry stems in spring.