Lateral bud development and shoot growth in low-pruned Morus alba as affected by stem orientation

Two phases of bud activity were identified in the new growth of one-year-old erect coppice shoots on 11-year-old low-pruned stumps of mulberry (Morus alba L. cv. Shin-ichinose) in spring, the sprouting phase in which the majority of the buds, including the basal ones, sprout and elongate, and the dominance phase (starting 4–5 weeks after sprouting) during which the upper laterals begin to assert dominance and suppress the growth of lower laterals, becoming new leading shoots. In contrast, arching before sprouting markedly inhibited buds on the under side, leading to poor shoots. By late April, the sprouts on the upper side grew readily into new erect shoots, resulting in considerable dominance over those from the lateral sides. Of these erect shoots, those located closer to the stem base grew more in May and June. The effects of arching made during the sprouting phase (late April) on bud activity and shoot lengths were generally similar to those of earlier archings before spring bud bursting. Separation of the shoots from the upper and under sides by longitudinal, horizontal splitting of the arched stems in late April did not affect the inhibited elongation of the shoots from the under side. These results suggest that in the response to arching before and in late April, the effects are related to spring bud bursting and gravimorphism. In contrast, arching during and after the dominance phase (May) had no gravimorphic effects on growth of the shoots on the upper side, although there was a stimulation of outbreak of the buds on the upper side, which remained dormant during spring bud bursting. Continuous basal applications of abscisic acid in aqueous solution inhibited bud break and shoot growth of the postdormant erect stem segments, and defoliation of the new shoots markedly. In contrast, similar applications of an ethylene-releasing compound, Ethephon, depressed shoot elongation slightly, but enhanced defoliation greatly. Gibberellic acid (GA₃) stimulated shoot elongation, but depressed leaf enlargement.     

六盘山东西两侧苹果物候期对气候变化的响应

利用六盘山东西两侧甘肃平凉市的崆峒、静宁站1971—2008年气温资料及1987—2008年在崆峒所设苹果观测点物候观测资料,分析了气候变化对苹果物候期的影响。结果表明:在全球气候变暖的背景下,甘肃平凉自1971年以来,气温呈现出明显的线性上升趋势,且以冬季和春季增温为主,气温稳定通过≥10℃的积温增加;受此影响,苹果叶芽开放、展叶、开花等成熟前的发育期提前14~18d,且六盘山东侧春季的苹果物候期提前的变化速率明显大于西侧;气候变暖增加了果树春季开花受冻的危险,通过苹果与霜冻灾害的相关分析,结果得到临界值:在4月11—20日、4月21—30日及5月1—10日苹果开花期,地面最低温度≤-2.0℃,且连续≥2d时,苹果受冻面积分别达到80%、90%和100%。     

Gravimorphism in Trees: 4. The Effect of Gravity on Flowering

Experiments with several varieties of fruit tree have shownthat, in apple, growing the whole tree horizontally had a markedstimulatory effect on flowering as compared with verticallygrown trees, but in similar experiments with cherry, plum, andblackcurrant the position of the tree relative to gravity hadlittle effect on flowering. Training of individual brancheshorizontally had no significant effect on the flowering of anyof the fruit tree varieties tested. By contrast, tying the upwardlygrowing branches of young Japanese larch trees into horizontaland downwardly directed positions led to pronounced increasesin the initiation of male cones, especially in favourable years.The male flower buds occur typically on all sides of trailingshoots and on the lower sides of horizontal shoots, and it isshown experimentally that the criterion is the physically andnot morphologically lower side. In birch there appears to beno increase in flowering when gravimorphic treatments are applied.     

Gibberellins in Diffusates from Shoots of Apple Trees

Excised shoot apices, leaves and internodes from shoots of apple trees (Malus×domestica) give off gibberellins by diffusion on agar. A methanol extract of the agar was prepared, the extract separated on thin layer plates, and the gibberellin activity estimated by means of Rumex and lettuce hypocotyl bioassays. The largest amounts of gibberellin are found in diffusates from the shoot apex, the two upper leaves and the two upper internodes. Several promotive fractions are found on the chromatograms as well as growth inhibitors. Removal of young leaves retards elongation of the internodes. Probably gibberellins produced in young leaves exercise some control over this process. The growth regulators Alar and CCC also retard internode elongation. Diffusates from shoots treated with these substances were also examined. Preliminary results suggest that the amount of diffusible gibberellins from treated shoots is not reduced.     

THE NATURE OF THE DIRECTIVE INFLUENCE OF GRAVITY ON THE ARRANGEMENT OF ORGANS IN REGENERATION

1. When leaves of Bryophyllum calycinum are suspended in moist air in a vertical plane and sidewise, roots and shoots are formed exclusively or predominate in the notches on the lower side of the leaves. When pieces of stems of the same plant are suspended horizontally in moist air, roots develop on the lower side of the stem, with the exception of the extreme basal end where they may develop on both sides. 2. The writer has suggested in a preceding paper that this directive influence of gravity on the arrangement of the regenerating organs may be due to the combination of two factors. The first factor is gravity, which causes a slightly greater collection of sap on the lower side of these organs, and as a consequence roots develop a little more quickly on the lower than on the upper side. The second factor is of an inhibitory character inasmuch as quite generally organs which grow out first, or which grow quickly, have a tendency to retard or inhibit the growth of similar organs in other places. 3. The writer was able to prove the action of this inhibitory factor by cutting off the lower edges of leaves suspended sidewise in a vertical plane or the lower halves of stems suspended in a horizontal plane (in moist air). In this case roots developed as abundantly on the upper side of these organs as they otherwise would have developed on the lower side. 4. It was, however, still necessary to prove the idea that gravity causes sap to collect in larger quantity in the lower parts of organs. This gap is filled by the present paper in which it is shown, first, that in the leaves suspended in moist air a red pigment is formed which has a tendency to collect gradually in the lowest parts of the leaf when the latter is suspended in a vertical plane. This red pigment serves as an indicator for the distribution of sap in the leaf and thus shows directly the tendency of the sap to collect in greater abundance on the lower edge of a leaf suspended in a vertical plane. Second, it is shown that when leaves or stems of Bryophyllum are suspended, in the way described, under water instead of in moist air, roots develop on the upper side as well as on the lower side. The directive effect of gravity upon the arrangement of organs disappears in this case since the abundance of the outside water makes the effect of a slight difference in the distribution of sap between the upper and lower side a negligible factor. Third, it is shown that the dry weight of the lower half of leaves suspended sidewise for several weeks in moist air in a vertical plane is greater than that of the upper half when roots and shoots are formed on the lower side only. This indicates that material from the upper half flows into the growing organs of the lower half. No such difference between upper and lower half of leaf is found when the leaves are suspended in the same way in water and roots and shoots are formed on both sides of the leaf. 5. It is shown that when a leaf connected with a piece of stem is suspended in moist air the red pigment goes into the stem instead of collecting in the lower part of the leaf, thus supporting the view expressed in a preceding paper that the inhibitory action of the stem on the root and shoot formation in a leaf of Bryophyllum is due to the fact that the material available in the leaf for organ formation is naturally sent into the stem.     

丛栽茶树树冠小气候及其对新梢生育和生化成分的影响

1 引言 为了获得优质高产的茶叶,需通过修剪养蓬等方法,使茶树形成宽广而整齐的树冠。丛栽茶树的树冠多呈馒头形,由于方位不同,形成了树冠内光、温、湿、风等因子的差异,因而影响了茶树的物候期及生理生化变化。因此,探讨树冠小气候特征及其对茶树新梢生育和生化成分的影响,在理论和生产实践上均有意义。有关这方面研究已有一些报道,但对茶树树冠小气候特征及其茶树新梢生育和品质成分的影响尚未见报     

WHITE PINE SHOOTS: ROLES OF GRAVITY AND EPINASTY IN MOVEMENTS AND COMPRESSION WOOD LOCATION

Pinus strobus L. trees were grown on a clinostat. Although elongating shoots moved in almost the reverse of the normal pattern, they reached a normal original angle. Compression wood (CW) formed only on the upper side of branches opposite where CW had previously formed. Neither treatments to remove epinasty (girdling branches, removing leaders and branches), nor treatments to bend branches out of position changed CW distribution. On trees grown off the clinostat, branches bending upwards after removal of the terminal formed CW on the upper side before reaching vertical. Main stems could form CW on the upper side after having been tipped to induce CW formation on the under side. It is suggested that epinasty is not involved in either early shoot movements or in compression wood location and that when gravity stimulates CW formation on the under side of a shoot it preconditions the upper side for CW formation, thus establishing an equilibrium position for the shoot.     

Morphogenesis and cell wall changes in maize shoots under simulated microgravity conditions.

Various plant organs show a spontaneous curvature on a three-dimensional clinostat. Changes in the cell wall metabolism underlying the curvature were examined in maize shoots. In coleoptile nodes, no differences were detected in either the level or the composition of cell wall polysaccharides between the convex and the concave halves. However, the convex side showed a higher activity of (1 --> 3),(l --> 4)-beta-glucan breakdown, which appears to be associated with the curvature. In the elongating region of coleoptiles, the accumulation of wall polysaccharides occurred in the convex side. There was no significant difference in the glucanase activity between both sides. Thus, the spontaneous curvature in different regions of maize shoots may be brought about through different mechanisms under simulated microgravity conditions.     

Effects of shoot bending of apple trees on accumulation and translocation of14C-labelled assimilates

The translocation of¹⁴C-labelled assimilates from a single leaf in bent and intact apple shoots was studied in varying stages of shoot development. In actively growing shoots¹⁴C-labelled assimilates translocated from the treated leaf and accumulated mainly in the shoot apex. In moderately growing apple shoots radioactive assimilates were translocated from the treated leaf in both directions towards and down the shoot. In apple shoots showing only slight growth activity the¹⁴C-labelled assimilates were transported from the treated leaf mainly to the base of the shoot, stem and roots. Bending shoots changed the pattern of distribution of radioactive assimilates. Bending actively and moderately growing shoots resulted in higher concentration of 14-carbon in the shoot apex than in controls. In slowly growing and non-growing apple shoots bending caused a higher accumulation of radioactive assimilates in the bent section than in an equal section of control shoots.     

苹果多酚氧化酶双链RNA干扰（RNAi）研究

以成熟苹果果实的RNA为模板,经RT—PCR扩增并克隆苹果多酚氧化酶(APPO)长度为710bp的反义、正义基因片段。以副球菌中类胡罗卜素合成有关的(crtW crtY)融合基因片段YYT为间隔区。将APPO反义基因片段、YYT和APPO正义基因片段串联,构成全长为2446bp的DNA并插入到植物双元载体pYPX145中,构成可表达苹果多酚氧化酶双链RNA的植物双元载体pYF7704。以根癌农杆菌介导的叶盘转化法转化苹果栽培品种红富士,通过50mg／L卡那霉素筛选和GUS检测,获得了转基因苹果抗性芽。荧光定量RT—PCR检测结果显示,转基因苹果抗性芽内多酚氧化酶基因的干扰效果达91．69％以上,研究结果证实多酚氧化酶双链RNA干扰在转基因苹果上是可行的。     

Sorbitol and other carbohydrates in dormant apple shoots as influenced by controlled temperatures

The influence of controlled temperatures on levels of sorbitol and other carbohydrates was determined to provide further information on dormancy of apple trees (Malus sylvestris Mill.). For 3 years, 2-year-old “Red Delicious” apple shoots were collected from mature trees in an orchard at intervals during the autumn and winter, and shoots were stored for 6 hr to 1 week at temperatures from 18 to ?60 °C. Sorbitol and other carbohydrates were estimated in the sap or wood by gas chromatography.Controlled temperatures had a marked influence on the carbohydrate content of excised 2-year-old apple shoots. Levels of sorbitol in the sap were maximum at ?0.6 °C. The increase was greatest at the earliest sampling before complete hardening had occurred in each of the 3 years tested. Total sorbitol in the wood was less influenced by storage at various controlled temperatures than sorbitol in the sap. Levels of fructose, glucose, and sucrose in the wood were higher at temperatures below ?0.6 °C than at warmer temperatures. Levels of starch were usually inversely related to soluble sugars.     

Architectural analysis of 1-year-old apple seedlings according to main shoot growth and sylleptic branching characteristics

Main shoot and sylleptic shoot growth characteristics were measured during and after the first year of growth of 255 Telamon x Braeburn apple seedlings. Although mean main shoot growth characteristics between branched and non-branched trees were significantly different, many non-branched trees expressed similar main shoot growth to branched trees. The variables describing length, number and position of the sylleptic shoots were used to classify branched trees into architecturally different groups. A continuum from trees with few and short shoots to trees with many long shoots is observed. The release of axillary buds from apical dominance is not under complete control by the apical meristem. Genetic seedling difference at the level of roots presumably plays an important role in sylleptic branching. Genetic variation in terms of number, position, and subsequent elongation of sylleptic shoots is clearly observed.     

Transgenic Tobacco and Apple Plants Expressing Biotin-binding Proteins are Resistant to two Cosmopolitan Insect Pests,Potato Tuber Moth and Lightbrown Apple Moth,Respectively

Tobacco (Nicotiana tabacum cv. Samsun) and apple (Malus x domestica cv. Royal Gala) plants expressing avidin or strepavidin were produced using Agrobacterium tumefaciens-mediated transformation. ELISA assays showed that avidin expression ranged from 3.1 to 4.6 microM in tobacco and from 1.9 to 11.2 microM in apple and streptavidin expression ranged from 11.4 to 24.5 microM in tobacco and from 0.4 to 14.6 microM in apple. Expressed at these levels, both biotin-binding proteins conferred a high level of insect resistance on transformed tobacco plants to larval potato tuber moth (PTM), Phthorimaea operculella (Zeller) (fam. Gelechiidae) and on apple plants to larvae of the lightbrown apple moth (LBAM) Epiphyas postvittana (Walker) (fam. Tortricidae). More than 90% of PTM larvae died on tobacco plants expressing either avidin or streptavidin genes within 9 days of inoculation. Mortality of LBAM larvae was significantly higher (P < 0.05) on three avidin-expressing (89.6, 84.9 and 80.1%) and two streptavidin-expressing (90 and 82.5%) apple plant lines than on non-transformed control plants (14.1%) after 21 days. Weight of LBAM larvae was also significantly reduced by feeding on all apple shoots expressing avidin and on apple shoots expressing streptavidin at levels of 3.8 microM and above.     

Comparative survival rates of oriental fruit moth (Lepidoptera: Tortricidae) larvae on shoots and fruit of apple and peach

Studies were designed to examine the effects of host plants on oriental fruit moth, Grapholita molesta (Busck) (Lepidoptera: Tortricidae), survival. G. molesta larval survival in the orchard was comparable between apple (Malus spp.) and peach (Prunus spp.) shoots, indicating that both host species can harbor large larval populations during the early season. G. molesta larvae used multiple shoots for feeding and development on peaches but usually only damaged single shoots in apple. Survival differences were present between peach and apple fruit, but this survival was affected by fruit maturity level. Generally, larval survival higher was in ripening peach fruit than in green, immature apple fruit. Larval survival varied among several apple cultivars, indicating that cultivar-level variability needs to be considered. These host-associated effects may impact efforts to predictively model G. molesta populations in commercial orchards where multiple host plant species, or different cultivars of the same species are often grown in proximity. Thus, host-associated dynamics should be included into future population models that underlie management programs.     

Patterns of leaf size and morphology in relation to shoot length in Tsuga canadensis

Summary Pattern of change in leaf character was assessed along the length and around the circumference of Tsuga canadensis (L.) Carr. shoots of different length classes. Leaf size decreased, and number of leaves per unit length of shoot increased, with decrease in shoot length. Acropetally along the shoots, lamina length and width decreased, relative petiole length increased, apices became more pointed, and leaf margins bore more teeth. Around the shoot, from upper to side, and to lower surfaces, leaf size and number of marginal teeth in the proximal halves of leaves increased. These patterns were related both to production of preformed versus neoformed leaves, though their separation was indistinct, and to secondary orientation of leaves by twisting in their petiolar regions into two major bi-lateral ranks. An additional minor rank occurred along the upper surfaces of the shoots where secondary orientation of the leaves was minimal. Surface features of leaves did not differ in any obvious manner. Leaves on sylleptic shoots, which by definition were all neoformed, exhibited similar patterns, but were generally smaller than those on their parent shoots.     

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.     

Photonastic Control of Leaflet Orientation in Melilotus indicus (Fabaceae)

Leaflet orientation in Melilotus indicus (L.) All. Is under photonastic control during the day and nyctinastic control during the night, but also exhibits a diaphototropic (solar-tracking) response. Detached leaves with the two lateral leaflets excised were used to study the solar-tracking capability of the terminal leaflet. Perception of the photonastic excitation is located in the pulvinule. The lower (abaxial) and upper (adaxial) surfaces perceive photonastic excitation, which results in concomitant contraction of the side exposed to light and/or expansion of the opposite side. Steady state laminar elevation is determined by the fluence rates of the light incident simultaneously on the opposite sides. Light sensitivity of the lower side exceeds that of the upper. Response to photonastic excitation of either side is affected by angle of incidence of the light, but angular dependence is restricted to a limited range of angle of incidence, which differs for the two sides. This may be accounted for by the different topography of the two pulvinar surfaces and the localization in them of the light-sensitive tissues.     

Comparison of some apple latent viruses

Apple latent viruses were eliminated from, the tips of apple shoots by exposure to a temperature of 36 °C for various periods. The length of treatment needed to eliminate a particular virus differed from plant to plant, but viruses were always inactivated in the same order: first chlorotic leaf spot, followed by stem pitting and finally Spy decline. Quince plants developed sooty ring-spot and bark necrosis when inoculated with buds from some heat-treated apple clones infected with Spy decline virus. Only chlorotic leaf spot virus was transmitted to herbaceous hosts by sap extracts from apple leaves, petals and fruits, and returned from herbaceous plants to apple. This virus, isolated from either apple or cherry, caused a dark green mottle on peach leaves.     

Distribution of labelled assimilates within a young apple tree after supplying14CO2to a leaf or shoot

Labelled carbon dioxide was supplied for 22 hrs to a leaf of the leader or to the lateral shoot in two-year-old apple seedlings. The distribution of radioactive assimilates within the plant following this treatment was investigated by using radioautography. The transport of labelled assimilates from the young leaf of the leader was very meagre and affected only parts of the stem and the leaves situated in the close vicinity of the treated leaf. The¹⁴C-labelled assimilates from the mature leaf of the leader were transported in a considerable amount to the apex and to the other leaves of the leader. They were also found in an appreciable amount in the stem and the roots, as well as in some lateral shoots. After supplying¹⁴CO₂ to the lateral shoot remarkable transport of labelled assimilates was observed. Radioactivity was detected in the tip and in the youngest leaves of the leader, as well as in the roots. Their path in the stem was studied by dissecting the plant and examining the cross section from each internode. This method revealed that the assimilates from the treated leaf or shoot were transported downward only on one side of the stem in a helical pattern. The lateral shoots situated on the radioactive side of the stem were also labelled, whereas those situated on the opposite (non-radioactive) side were not labelled.