树木复幼的研究概述

幼龄树木通常具有良好的生根能力、旺盛和通直的生长习性与较强的抗性,然而随着树木的成熟这些特性会逐渐丧失.复幼是使成熟树木重现某些幼态性状的过程.成熟树木的复幼和幼态保持是林木生产、无性繁殖、遗传改良和生物技术在林木中应用中十分重要的科学问题.本文对树木的组织和器官保持幼态的特性、顶端分生组织表达幼态的潜能、与复幼相关的生理、生化和分子生物学以及复幼方法等方面的研究进行了概述,并对今后的研究和需要解决的关键问题提出了意见和建议.     

叶异形水生植物不同发育阶段叶片的结构和无机碳获取策略

以睡莲(Nymphaea tetragona Georgi)、萍蓬草(Nuphar pumila (Timm) de Candolle)、条叶萍蓬草(Nuphar sagittifolia Pursh)、眼子菜(Potamogeton distinctus A. Bennett)、南方眼子菜(Potamogeton octandrus Poir)和泽泻(Alisma plantago-aquatica L.)6种叶异形水生植物为材料,对它们的叶绿素含量、气孔性状、解剖结构和HCO₃^-利用等指标进行分析,比较了两种不同发育阶段叶片结构和无机碳获取策略的差异。结果显示,幼态叶比成熟叶的叶片更薄,具有更少的细胞层数,幼态叶上下表面均不具备气孔,而成熟叶上表皮有气孔。说明幼态叶在结构上增加细胞比表面积,增加水下吸收无机碳的能力,而成熟叶的结构能更好地吸收大气中的CO₂。pH-drift分析结果证明,幼态叶具有更高获取水下无机碳的能力,以适应沉水环境。本研究还发现眼子菜和南方眼子菜的幼态叶可以利用水体中HCO₃^-为额外碳源,更有利于其在沉水环境中生长。研究结果阐明了叶异形水生植物不同发育阶段叶片结构和利用无机碳获取策略对水下和气生环境的适应性。     

幼态成熟学说与生物的形态演化

长期以来,生物学家通过比较形态学的研究,发现某个种类或其器官和另一个种类或其器官的幼年期很相象,因而推测这个种类或其器官就是从那个种类或其器官尚处于幼年期就成熟而发展起来的,这就是生物形态进化的幼态成熟学说。由于生物学家早就注意了这种现象,所以在文献上“幼态成熟”的概念出现了不少的同义语,现在多用neoteny这个词,一般翻     

复幼促进核桃不定根发生的DNA甲基化机制探讨

该研究以核桃的复幼和成龄插穗为材料,通过甲基化修饰依赖性内切酶测序技术(MethylRAD-Seq),在全基因组水平上检测成龄与复幼插穗中DNA甲基化位点分布特征,进一步对复幼处理前后插穗中差异甲基化位点相关基因的表达情况进行分析。结果显示:(1)复幼处理可显著降低核桃插穗的DNA甲基化水平。(2)功能富集分析结果显示,差异甲基化位点相关基因主要参与油菜素内酯信号转导、次级代谢产物生物合成和木质素生物合成等功能,参与光合作用、MAPK(mitogen-activated protein kinase, MAPK)信号通路、果糖和甘露糖代谢、cAMP(cyclic AMP, CAMP)信号途径和苯丙烷生物合成等代谢通路。(3)qRT-PCR分析结果显示,复幼处理前后,不定根发生的关键调控基因NAC1、ARF5、ARF6和WRKY22在复幼和成龄材料中具有不同的表达模式。研究认为,复幼处理降低了核桃插穗中基因组DNA的甲基化水平,进而影响不定根发生过程关键功能基因的表达,可能是复幼调控核桃不定根发生能力的重要途径。     

树木的冬态

一.掌握树木冬态的意义冬季来临,植物进入了休眠的时期,落叶树种绿叶脱落露出树干、枝条和芽苞,外观上呈现和夏绿季节完全不同的形态,一般称为树木的冬态。人们一般对于树木的花、果和叶的观察较多,而对树木的各态常较生疏,因而容易以为树木的枝条和冬芽的形态是大同小异,没有多大差别。实际上,如留心观察,它们不仅形态差异很大,而且有一定的特点,是冬季研究树木形态的好材料,树木冬态的研究还有下列几个方面的意义: 1.我国领土辽阔,各地冬季的长短不一,但最少有3—4个月(长江流域),多可达半年之久(东北,内     

影响籼稻体细胞胚胎发生几个因素的研究

以 IR36、IR50、IR52及 IR54等品种的幼穗及成熟种子为材料,研究了蔗糖浓度、2,4-D、NAA、激动素及脱落酸对体细胞胚胎发生、结构的保持及植株分化的影响。6%蔗糖有利于胚性愈伤组织的诱导;3%的有利于胚性结构的保持及植株分化。当培养基中不含2,4-D,而含激动素与 NAA 时,幼穗直接出芽;当不含激动素而含2,4-D与 NAA 时,外植体产生非胚性愈伤组织;当不含 NAA 而含2,4-D 与激动素时,外植体产生胚性愈伤组织。认为,2,4-D与激动素是籼稻体细胞胚胎发生的基本因素,而 NAA 的作用是不明显的。不同外植体(幼穗与成熟种子)的体细胞胚胎发生,对2,4-D 与激动素的反应略有不同,幼穗更为敏感。在继代培养基中,加入低浓度的脱落酸有利于胚性结构的保持。随着继代世代的延续,分化培养中愈伤组织所表现出的绿色生长点状物不能发育成完整植株。     

寡齿新银鱼同工酶及其与幼态持续的关系

采用聚丙烯酰胺垂直板状连续电泳方法,对幼态持续(neoteny)的寡齿新银鱼(Neosalanx oligodontis Chen)13种同工酶的18个位点进行研究,并进行乳酸脱氢酶热变性实验。结果表明ADH、GOT、α-GPDH、LDH、MDH、ME、POX和SOD表现出一定的幼态持续的特征,其中LDH由A、B两个位点编码,C位点不表达,是因为个体发育早期C基因尚未表达时发生幼态持续的结果。ES和IDH无幼态持续特征。α-AMY、FUM和CAT因数据不足,未进行分析。寡齿新银鱼同工酶基因表达中幼态特征的表现为研究鱼类幼态持续的产生机制和遗传基础提供线索。     

树木抗旱机理研究进展

干旱是树木成活与生长的重要限制因素之一。研究树木的抗旱性,有助于了解树木的干旱适应性机制,探求树木抗旱的适宜调控措施,对充分发挥森林的生态效益具有重要作用。本文从树木的水分关系、净光合速率与蒸腾速率、叶片的δ13C值、木质部导管空穴、光合机制与抗氧化保护机制、渗透调节、脱落酸和C4植物的抗旱机理及树木的抗旱基因与遗传特性(包括水通道蛋白、逆境信号转导、树木抗旱性的遗传基因工程)方面对树木抗旱机理研究进行了综述。     

含硝化抑制剂DMPP复合肥对日光温室芹菜生长和营养品质的影响

通过田间试验研究了含硝化抑制剂DMPP复合肥对日光温室芹菜生长和品质的影响. 结果表明,与普通复合肥相比,一次基施DMPP复合肥67.5和54.0 kg·hm^-2 氮处理分别使芹菜增产5.78%和10.14%; DMPP复合肥可降低芹菜可食部分硝酸盐含量,提高Vc、游离氨基酸、可溶性糖及氮、磷含量. 与分次施用相比,适当减少DMPP复合肥施用次数和用量可提高芹菜产量并改善其品质,降低生产成本.DMPP复合肥在施入土壤中后具有显著的硝化抑制作用,延缓了菜地土壤铵态氮向硝态氮的转化,降低了氮素向水体迁移的风险.芹菜收获后土壤中全氮、铵态氮、硝态氮残留较多,有利于保持地力.     

竹盲走螨对竹裂爪螨的捕食功能

在实验室模拟条件下,系统研究了竹盲走螨对竹裂爪螨的控制作用.结果表明,在25±0.5 ℃条件下,竹盲走螨对竹裂爪螨各螨态的功能反应均属HollingⅡ型.在同一温度条件下,雌竹盲走螨成螨对竹裂爪螨各螨态的处置时间依次为卵<幼螨<前若螨<后若螨<雌成螨.竹裂爪螨卵、幼螨、若螨、雌成螨共存时,竹盲走螨嗜食卵、幼螨和前若螨（Q>1）,但其对卵与幼螨及幼螨与前若螨无偏嗜现象.当竹裂爪螨密度低于9头时,竹盲走螨的产卵量随密度增加而增加;9～15头时,其日平均产卵量保持在每雌2粒左右;超过15头以后,产卵量反而下降,说明猎物密度过高对捕食者生存、繁殖存在干扰作用.     

IN VITRO REJUVENATION OF BETULA (BETULACEAE): MORPHOLOGICAL EVALUATION

The extent of rejuvenation that occurs during in vitro culture and propagation of Betula was determined. Comparisons were made between half-sib seedlings and micropropagated, grafted, and cutting-propagated mature-phase birch plants grown under similar conditions. To measure relative levels of juvenility, three clones were examined at 1, 4, and 8 mo postpropagation, for differences in stem and leaf morphology and the presence or absence of reproductive structures. Numerous morphological indicators of phase change in Betula were identified. Micropropagated plants are not initially morphologically identical to conventionally propagated mature plants and display many features characteristic of seedlings. Micropropagated plants that exhibited juvenile morphology developed mature morphology more rapidly than did plants grown from seed. However, some mature-phase morphological characteristics did not return to micropropagated plants during the time frame of the study. Rejuvenation of Betula appears to occur during in vitro micropropagation, but the level of juvenility that is regained may not be equivalent to that of a seedling. Not all morphological indicators of phase change are affected equally by in vitro rejuvenation.     

Rejuvenation of a 100-year-old Sequoiadendron giganteum through in vitro meristem culture. I. Organogenic and morphological arguments

True-to-type cloning of mature trees, especially when they do not sprout from their base, remains problematic. Special attention is focused on the shoot apical meristem, since it is an obvious choice for vegetative propagation. In Sequoiadendron giganteum a meristem removed during budbreak from a 100-year-old tree regenerated a truly rejuvenated line that exhibited the same juvenile characters as the juvenile clone used as control, especially in regard to morphological traits and organogenic capacity, and as manifested by the ability to produce adventitious roots in vitro. This rejuvenation has been maintained for 3 years in both in vitro and ex vitro conditions. This result is discussed in terms of inhibitory correlative systems acting within the donor tree in situ, especially as concerns miniaturization of the explant.     

Multiple adventitious shoot formation in Spanish Red Cedar (<Emphasis Type="Italic">Cedrela odorata</Emphasis> L.) cultured <Emphasis Type="Italic">in vitro</Emphasis> using juvenile and mature tissues: an improved micropropagation protocol for a highly valuable tropical tree species

Cedrela odorata L. is a valuable tropical tree widely appreciated for its wood. This species confronts serious problems due to both overexploitation of its natural populations and its susceptibility to the Meliaceae borer Hypsipyla grandella, which destroys the apical meristems and produces structural deformations. The rapid introduction of new varieties through clonal forestry has been demonstrated to be the most effective way to improve the production of perennial plantation species. In this work, we report both a protocol for the rejuvenation of elite mature trees of C. odorata and the optimization of an in vitro culture system to scale up micropropagation. Several media formulations and the use of temporary immersion culture in bioreactors were evaluated. The addition of 20% coconut water to TY17 medium increased the number of adventitious shoots from hypocotyl segments to an average number of 4.68 shoots per explant. To replace coconut water and to define the culture medium, several cytokinins were tested at various concentrations; however, none of them produced the effect of coconut water. Rejuvenation of elite mature individuals was investigated by ex vitro grafting of mature tree twigs onto 3-mo-old juvenile trees. Although the grafting had a positive effect on the micropropagation of mature material, the multiplication rate of 1.5 new shoots per explant did not compare to the organogenic capacity of younger materials. Shoot and root elongation as well as acclimatization to ex vitro conditions were carried out in a temporary immersion culture of juvenile material using BioMINT® bioreactors. A 3.5-fold increase in shoot elongation and a 4-fold increase in root elongation were achieved compared to material cultured on semisolid media. Furthermore, this culture system allowed for 98% effectiveness in the soil adaptation of the in vitro-grown plants. The scaled-up multiplication capacity over a period of 6 mo calculated for the system is above 16,000 plants per mother plant with young materials but is only 125 with mature materials.     

Small RNAs of Sequoia sempervirens during rejuvenation and phase change

In this work, the population of small RNAs (sRNAs) was studied in the gymnosperm Sequoia sempervirens during phase changes, specifically in the juvenile, adult and rejuvenated plants obtained in vitro. The potential target genes of Sequoia sRNAs were predicted through bioinformatics. Rejuvenation is a pivotal process in woody plants that enables them to regain their growth potential, which results in the recovery of physiologic and molecular characteristics that were lost when the juveniles mature into adult plants. The results from the five repeated graftings of juvenile, adult and rejuvenated plants in vitro showed that sRNAs could be classified into structural RNAs (Group I), small interfering RNAs (Group II), annotated microRNAs (Group III, and unannotated sRNAs (Group IV). The results indicate that only 573 among 15,485,415 sRNAs (Groups III and IV) had significantly different expression patterns associated with rejuvenation and phase change. A total of 215 sRNAs exhibited up‐regulated expression patterns in adult shoots, and 358 sRNAs were down‐regulated. Expression profiling and prediction of possible target genes of these unique small RNAs indicate possible functions in the control of photosynthetic efficiency and rooting competence abundance during plant rejuvenation. Moreover, the increase in SsmiR156 and decrease in SsmiR172 during plant rejuvenation suggested that these two microRNAs extensively affect phase transition.     

Rejuvenation of a 100-year-old Sequoiadendron giganteum through in vitro meristem culture. II. Biochemical arguments

The phenomena of phase change and rejuvenation are characterized mainly by morphological and physiological criteria. Thus far, biochemical assessments have been relatively limited. In Sequoiadendron giganteum , techniques of sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and miniaturized two-dimensional gel electrophoresis were applied to a meristem-derived line from a 100-year-old tree to attest the basic origin of the resulting rejuvenation observed from morphological and organogenic standpoints in vitro as well as after acclimation in outdoor conditions. The membrane-associated protein J16, which characterizes the juvenile status was detected in both the juvenile control and the rejuvenated line, while in the original mature form it was totally lacking. In addition, two-dimensional electrophoretic analysis of protein patterns of single meristems belonging to the mature and the rejuvenated form suggested that rejuvenation might involve a drastic modification of the protein content within the meristem itself.     

Adventitious Root Initiation In Reciprocally Grafted Leaf Cuttings from the Juvenile and Mature Phase of Hedera helix L

Reciprocal grafts involving leaf petioles and lamina of thejuvenile and mature phase of Hedera helix were prepared to determinethe relative importance of petiole and lamina on root initiationin leaf cuttings. The results indicated that root initiationwas mainly a function of the potential of cells in the petioleto respond in a specific morphogenetic pattern. Initially, rootinitiation was unaffected by the type of lamina. However, overtime, a factor translocated from the juvenile lamina promotedroot initiation in the mature petiole. This factor decreasedthe time taken for root initiation and increased the numberof roots per mature petiole. There was no evidence for an inhibitorfrom the mature lamina affecting root initiation in the juvenilepetiole. Key words: Rejuvenation, root initiation, rooting cofactors     

Rejuvenation of Sequoia sempervirens in Vitro: Changes in Isoesterases and Isoperoxidases

Rejuvenation, as evidenced by restored rooting competence, ofSequoia sempervirens by a series of repeated grafting of adultshoot tips onto juvenile rootstocks in vitro was confirmed.Complete restoration of rooting competence was achieved aftergrafting repeatedly five times. The rejuvenation was correlatedwith a disappearance of adult-associated esterase and peroxidaseisozymes and an appearance of isoesterases and isoperoxidasesthat were characteristic of juvenile-phase shoots. These esteraseand peroxidase isozymes could serve as markers to assist phasechangeinvestigations. (Received May 8, 1995; Accepted November 6, 1995)     

Gas exchange of juvenile and mature trees of <Emphasis Type="Italic">Alnus jorullensis</Emphasis> (Betulaceae) at sites with contrasting humidity in the Venezuelan Andes

The reduction of photosynthetic rates with tree age has been proposed as a major driver of the productivity declination along ontogeny. It is not clear, however, how environmental humidity affects stomatal conductance and biochemical potential of photosynthesis in trees belonging to different age-classes. We assessed daily cycles of gas exchange on leaves of juvenile and mature individuals of the tropical high-elevation tree Alnus jorullensis Kunth (Betulaceae), at two sites with contrasting precipitation in the Venezuelan Andes. Photosynthesis and stomatal conductance were higher in juvenile trees during the morning and at noon in the mesic site, and were in general similar between age-classes in the wet site. Under light-saturating conditions, the net photosynthetic rate was similar between the age-classes at the wet site and higher for juvenile trees at the mesic site, whereas stomatal conductance did not differ between age-classes and was higher at the wet site. Daily cycles of gas exchange and a type II regression model between photosynthesis and intercellular CO₂ concentration indicated that the better performance of juvenile trees at the mesic site was due to lower non-stomatal limitations. These results support the proposal that non-stomatal limitations—rather than stomatal ones—are involved in the decay of photosynthesis in mature trees, and suggest that such limitations may be evident only under drier conditions.     

江西九连山亚热带常绿阔叶林优势种空间分布格局

于江西九连山国家自然保护区设置4 hm2亚热带常绿阔叶林固定监测样地,用样方法对亚热带常绿阔叶林进行调查分析。应用点格局方法分析生境异质性是否影响树木分布并分析优势种红钩栲(Castanopsis lamontii)、米槠(Castanopsis carlesii)、罗浮柿(Diospyros morrisiana)和细枝柃(Eurya loquaiana)分布格局,对比存在生境异质性和排除生境异质性两种情况下优势树种不同生长阶段(幼树、小树、成年树)的空间分布格局以及不同生长阶段之间的空间关联性,探讨生境异质性之外的其它种群分布影响因子。结果表明:1)生境异质性效应显著影响九连山树木分布,4个优势树种在大尺度上存在明显的生境偏好;2)用完全随机零模型不排除生境异质性时,4个优势种总体及其不同生长阶段在0—30 m所有尺度上主要呈现聚集分布;3)用异质性随机零模型排除生境异质性后,4个优势种及其不同生长阶段的聚集程度显著下降,只在小尺度上(0—5 m)呈现聚集分布;4)4个优势种的幼树与小树均表现显著的正相关。红钩栲的成年树与幼树及成年树与小树总体表现不相关。米槠的成年树与幼树总体以无相关为主;成年树与小树之间总体呈正相关。小乔木罗浮柿的成年树与幼树之间在小尺度上(0—5 m)表现负相关或无相关,在较大尺度范围上总体表现正相关关系;小树与成年树在研究尺度上表现出正相关。灌木细枝柃的成年树与幼树,成年树与小树及小树与幼树之间在研究尺度范围内均呈现正相关关系;5)研究发现九连山优势乔木物种通过密度制约和Janzen-Connell效应释放空间,为其他物种共存提供条件,而优势灌木物种细枝柃没有表现出这两个效应。     

Phenylalanine ammonia-lyase,chalcone synthase and polyphenolic compounds in adult and rejuvenated hybrid walnut tree

Summary During the first growth phase of walnut (Juglans sp.) stump shoots, the concentrations of the two major phenolic compounds are not correlated with an increasing rate of shoot growth. The concentration of hydrojuglone glucoside (naphtoquinone) decreases as shoot growth rate increases, whereas the concentration of myricitrin (flavonol) remains constant. In contrast, phenylalanine ammonia-lyase (PAL, EC 4.3.1.5) activity is proportional to the growth rate of shoots. Rejuvenation, which induces a higher growth rate and vegetative propagation ability, results in an increase of both PAL and chalcone synthase (CHS, EC 2.3.1.74) activities and hydrojuglone glucoside/myricitrin ratio. Moreover, physiological ageing is characterized by an accelerated functioning of polyphenolic metabolism. Fluctuations in PAL activity are associated with changes in shoot growth rate and with rejuvenation, but PAL does not directly control the accumulation of flavonoid compounds during rejuvenation. On the contrary, mathematical correlation of CHS activity and flavonoid accumulation during annual shoot growth of both adult and rejuvenated trees, indicates that CHS is the rate-limiting enzyme of the pathway.