Interaction of Growth Retardants and Temperature in Growth, Flowering, Regeneration, and Auxin Activity of Begonia × cheimantha Everett

Soil application of CCC reduced stem and leaf growth in Begonia plants. This effect was evident with all concentrations tested at 18°C, whereas at 21 and 24°C no growth–retarding effect was observed with 2 × 10^?2 M CCC, and with 5 × 10^?3 M growth was even stimulated. Flowering was promoted by CCC in long day and neur–critical temperature, particularly under low light intensity in the winter. The formation of adventitious buds in leaves of plants grown at 21 and 24°C was stimulated when the plants received 5 × 10^?2 and 2 × 10^?2 M CCC, while 8 7times; 10^?2 M was inhibitory. In plants grown at 18°C bud formation was inhibited by all CCC concentrations. Root formation in the the leaves was usually stimulated by high CCC concentrations, while root elongation was reduced. The level of ether–extractable. acidic auxin (presumably IAA) in the leaves was lowered by CCC treatment of the plants, hut this required higher CCC concentrations at higt than at low temperature. When applied to detached leaves CCC stimulated bud formation at concentrations ranging from 10^?4 to 10^?2 M in leaves planted at 18 and 21°C. At 24°C budding was inhibited by 10^?2 M CCC, the lower concentrations being stimulatory also at this temperature. Root formation and growth were not much affected by CCC treatment of the leaves, but increased with the temperature. Soil application of Phosfon (4 × 10^?4 M) had no effect on growth and flowering, nov did it affect the subsequent regeneration of buds and roots in the leaves. In detached leaves Phosfon stimulated bud formation with au optimum at 10^?6 M. Root formation was stimulated by Phosfon at all temperatures, the optimal concentration being 10^?5 M, whereas root length was conversely affected. Foliar application of B-995 to intact plants and treatment of detached leaves greatly inhibited the formation of buds and had little effect on root formation. B-99D reduced the growth and delayed flowering in the plants.     

In vitro propagation of green-foliaged Dracaena fragrans Ker.

Callus tissue was induced in young stem segments cultured on MS based media supplemented with 0.25–0.5 mg l^-1 2, 4-D. Shoots were differentiated on media containing 0.5–1.0 mg l^-1 BA and 0.5–2.0 mg l^-1 IBA or 0.1–0.2 mg l^-1 NAA. The same media were suitable for shoot multiplication. Shoot elongation and rooting were strongly inhibited by BA and stimulated by auxins IBA and NAA. Medium containing 0.5 mg l^-1 IBA was optimal for rooting. Root elongation was stimulated by light and inhibited in darkness. Transfer of rooted plantlets to outdoor conditions was feasible and special hardening procedures were not required. Among more than 5000 plants produced by this procedure only 9 off-type plants with variegated leaves were found.     

Branch and root formation in Trifolium repens is influenced by the light environment of unfolded leaves

In plagiotropic plants, axillary buds on the stolon can be exposed to low red:far-red (R:FR) ratios, while the leaves may be positioned in the uppermost layer of the sward where they are exposed to a high R:FR ratio. We tested whether the light environment of unfolded leaves influences outgrowth of the axillary buds and the formation of nodal roots of Trifolium repens. Single plants were grown in a growth cabinet with high photosynthetic photon flux rate (PPFR) and a high R:FR ratio (F_HR_H, control), low PPFR and high R:FR (F_LR_H) or low PPFR and low R:FR (F_LR_L). In an additional treatment (SS), only stolons were shaded so that developing leaves grew into light conditions similar to the control treatment. Neutral shading (F_LR_H) had a minor effect on branching and did not influence root formation. A reduction in the R:FR ratio (F_LR_L) significantly delayed the outgrowth of axillary buds so that, compared to the control plants, the percentage of branched phytomers was reduced by 43% on the parent axis and by 75% on primary branches. Furthermore, the number of nodal roots per plant was reduced by about 30%. When only the stolons were shaded (SS), the percentage of branched and rooted phytomers was similar to that of the control plants. Extension of petioles and leaves was very variable, increasing the values in the F_LR_L treatment at least 2.5-fold compared with the control plants. It was concluded that the light environment of the unfolded leaves had a significant influence on the regulation of the outgrowth of axillary buds and that the high plasticity in petiole growth allows the positioning of the leaves in a light environment conducive to the stimulation of branch outgrowth. Received: 8 February 1997 / Accepted: 26 April 1997     

Shoot regeneration from petioles of coral bells (Heuchera sanguinea Engelm.) cultured in vitro, and subsequent planting and flowering ex vitro

Summary Successful shoot regeneration from petioles, leaves, and petioles with leaves cultured in vitro is reported in Heuchera sanguinea. Petioles or petioles with leaves regenerated more shoots than leaves alone. For culture, the optimum hormonal concentrations were 0.19 μM α-naphthaleneacetic acid combined with 0.44 or 4.4 μM benzyladenine in Murashige and Skoog-based (MS) medium: the regenerating rate and the number of shoots per explant were 60% and 8.6–9.7, respectively. Histological study on petiole culture showed dividing cell clusters including vascular tissues after 1 wk, callus including several dividing cell clusters at the periphery after 3 wk and then apical meristems with immature leaves after 5 wk. Rooting from the regenerated shoots was highest (95%) on MS medium containing 4.9 μM indole-3-butyric acid. Seventy-three percent of rooted plants were successfully acclimatized in pots. When they were cultured in the field, the plants grew and most flowered the following year over winter.     

银杏愈伤组织的形成及其中黄酮类化合物的产生

单一激素种类对银杏叶片,叶柄和幼茎愈伤组织的诱导中以NAA的效果最佳,2,4－D次之,6－BA最差,除胚乳外,胚,幼苗的胚根,子叶,幼茎,叶片和叶柄,以及成年树的嫩茎,叶片和叶柄各外植体在本试验条件下都能诱发愈伤组织,其中胚,子叶和叶柄的愈伤组织形成频率均可达到100．0％,叶片和幼茎在光照下的愈伤组织诱导频率比黑暗中的略高,而叶柄和胚根则相反,MS和DCR两种培养基都适合银杏幼苗叶片及叶柄愈伤组织的诱导,两者之间不存显著性差异,测得光照培养的3个组织系（ST1,ST2,ST3)中均含银杏黄酮甙元槲皮素,山柰素和异鼠李素,总含量分别为干重的0．35％,0．29％和0．14％,而黑暗中培养的这3个愈伤组织系则没有银杏黄酮的产生。     

The Response of Petioles of Glechoma hederacea to a Dynamic Light Climate

Abstract: In herbaceous vegetation patterns of light distribution may change over time. Prostrate plants growing in such a dynamic light environment may benefit from petioles that respond plastically to changing light conditions. In an experiment, the response of petioles of Glechoma hederacea to changing light conditions was analyzed. Treatments included continuous shade, continuous high light, a shift from shade to high light and from high light to shade when the plants had formed 10 ramets. In all four treatments, even petioles that had apparently ceased growing, were still able to elongate slightly but the extent of elongation decreased with the age of the petiole. In the oldest petioles relative extension rates were higher in shade than in high light. In plants that were exposed to full daylight in the second half of the experiment, even newly formed petioles were longer than those in plants that grew in full daylight continuously though they had elongated over a shorter period. In plants that were shaded in the second half of the experiment, only the youngest 4 to 5 petioles reached lengths similar to that in continuous shade. This mechanism may enable plants to keep young (productive) leaves in the upper layers of the canopy while other less productive leaves remain at lower levels of the vegetation.     

Scaling sun and shade photosynthetic acclimation of Alocasia macrorrhiza to whole-plant performance – I. Carbon balance and allocation at different daily photon flux densities

We determined the carbon allocation patterns and construction costs of Alocasia macrorrhiza plants grown at different photon flux densities (PFD) as well as the whole-plant carbon gain of these plants at different daily PFDs. Growth at high PFD resulted in thicker leaves with a higher leaf mass per unit area, and increased biomass allocation to petioles and roots, as compared to growth at low PFD. Increased allocation to petioles may have been necessary to support the heavier leaves, whereas increased allocation to roots may have been necessary to supply sufficient water for the higher transpiration rates in high PFD. Root biomass was highly correlated with the daily, whole-plant transpiration rate. Tissue construction costs per unit dry mass were unchanged by acclimation, but, since the mass per unit areas of leaves, roots and petioles all increased, construction costs per unit leaf area were much higher for plants grown at high PFD. On a per unit leaf area basis, daily whole-plant carbon gain measured at high daily PFD was higher in high- than in low-PFD-grown plants. However, on a per unit leaf mass basis, low-PFD-grown plants had a daily carbon gain at least as high as that of high-PFD-grown plants at high daily PFD. At low daily PFD, low-PFD-grown plants maintained an advantage over high-PFD-grown plants in terms of carbon gain because of their larger leaf area ratios. Thus, in terms of carbon gain, low-PFD-grown plants performed better than sun plants at low PFD and as well as high-PFD-grown plants at high PFD, despite their lower photosynthetic capacities per unit area. For high-PFD-grown plants, the higher construction costs per unit leaf area resulted in lower leaf area ratios, which counteracted the advantage of higher photosynthetic rates per unit leaf area.     

A rapid method for generating sufficient amounts of uniform genotype-specific material from the woody perennial grapevine for ion transport studies

Experimentation with woody perennials may be difficult due to slow plant growth and a lack of sufficient amounts of uniform plant material. In this study, we sought to determine whether rooted leaves could be used as a substitute for whole plants in ion accumulation studies. Grapevine leaves are particularly amenable for rooting since their petioles are of sufficient length for dipping in rooting hormone and for holding the leaf above the soil surface. To determine whether rooted leaves would be useful for salinity experiments, we investigated the ion uptake characteristics of rooted leaves derived from a backcross population that differed in Cl^– accumulation. Long-term ion accumulation studies conducted over several weeks and short-term radioactive uptake studies conducted over several hours were performed. The data showed that the Cl^– content of rooted grapevine leaves from different genotypes grown at 25 and 50 mM NaCl was similar to data reported by others. Short-term radioactive uptake assays did not always reveal differences in uptake between the genotypes. Therefore, we suggest that rooted leaves under certain conditions may provide a space-efficient method for generating sufficient amounts of plant material. This material could be used for studying whole plant, molecular and electrophysiological aspects of ion transport and for conducting experiments where root material from specific genotypes is required.     

LIGHT EFFECTS ON LEAF MORPHOLOGY IN WATER HYACINTH (EICHHORNIA CRASSIPES)

Water hyacinth leaves in natural populations vary from being long and thin-petioled to being short with inflated petioles. A variety of factors has been used experimentally to alter water hyacinth leaf shape, but what controls the development of leaf morphology in the field has not been established. We measured photosynthetic photon flux density (PPFD) and spectral distribution of radiation in a natural water hyacinth population. PPFD in the center of the water hyacinth mat was reduced to 2.7% of full sunlight, and the red to far red (R:FR) ratio was reduced to 0.28. When shoot tips of plants were exposed to artificial light environments, only plants in the treatment with a R:FR ratio comparable to that in the natural population produced leaves with long, thin petioles. Shoot tips in full sun or covered with clear plastic bags or bags that reduced light quantity without greatly altering light quality produced shorter leaves with inflated petioles. We hypothesize that the altered light quality inside a mat is a major environmental control of water hyacinth leaf morphology.     

长期弱光对苦草幼苗生长发育的影响

用遮光法研究弱光(5%、1%、0.5%、0.1%全光照)对苦草幼苗生长发育的影响,统计了苦草的生物学参数,测定了叶片叶绿素荧光参数。结果表明:1)0.1%组无新株萌发,随着实验时间的延长其余组新株萌发逐渐被抑制。2)随着实验时间增加和光照强度降低,老株叶片形成受到的抑制程度呈增大趋势;前20d时新株叶片形成未被抑制,但随着实验时间延长显著被抑制。3)老株、新株的叶宽均受到显著抑制。4)老株叶片的伸长显著被抑制,且随着光强降低叶片伸长的幅度呈显著降低趋势;前20天时新株叶长被促进,随着实验时间延长叶片伸长显著被抑制。5)随实验天数的增加,老株叶片光化学最大量子产量(Fv/Fm)呈显著降低趋势,第80天时相对电子传递速率(rETR)和非光化学淬灭(NPQ)显著降低。6)新、老植株根、茎、叶的鲜重均显著低于对照,且随着光照强度降低老株的茎重/株重和根重/株重呈增加趋势,而叶重/株重呈显著的降低趋势。第80天时苦草植株仍具有一定的光合能力,地下茎的生物量比例较高,因此,≤1%全光照下苦草植株具有较强的耐受能力。     

光质对五种不同生活型植物的器官发生和生长的影响

本实验对百合、虎头兰、非洲紫罗兰、斑叶海棠和烟草五种不同生活型材料在离体培养诱导器官发生过程中,对光质及黑暗条件的反应进行了研究。结果指出,作为地下芽的百合和虎头兰小鳞茎、原球茎的发生不依赖于光质条件,而作为地面芽和地上芽的非洲紫罗兰与斑叶海棠的不定芽发生,在1.40mw/cm~2的光强下,红光有促进作用,蓝光和黑暗却有抑制作用;烟草则是蓝光对其不定芽的发生有利,而红光和黑暗有抑制作用。     

Jasmonates Inhibit Flowering in Short-Day Plant Pharbitis nil

The role of jasmonates in the photoperiodic flower induction of short-day plant Pharbitis nil was investigated. The plants were grown in a special cycle: 72 h of darkness, 24 h of white light with lowered intensity, 24-h long inductive night, 14 days of continuous light. At 4 h of inductive night the cotyledons of non-induced plants contained about two times the amount of endogenous jasmonates (JA/JA-Me) compared to those induced. A 15-min long pulse of far red light (FR) applied at the end of a 24-h long white light phase inhibited flowering of P. nil. The concentration of jasmonates at 2 and 4 h of inductive night in the cotyledons of the plants treated with FR was similar. Red light (R) could reverse the effect of FR. R light applied after FR light decreased the content of jasmonates by about 50%. Methyl jasmonate (JA-Me) applied to cotyledons, shoot apices and cotyledon petioles of P. nil inhibited the formation of flower buds during the first half of a 24-h long inductive or 14-h long subinductive night. Application of JA-Me to the cotyledons was the most effective. None of the plants treated with JA-Me on the cotyledons in the middle of the inductive night formed terminal flower buds. The aspirin, ibuprofen and phenidone, jasmonates biosynthesis inhibitors partially reversed the effect of FR, stimulating the formation of axillary and terminal flower buds. Thus, the results obtained suggests that phytochrome system control both the photoperiodic flower induction and jasmonates metabolism. Jasmonates inhibit flowering in P. nil.     

The role of petioles in light acquisition by Hydrocotyle vulgaris L. in a vertical light gradient

In natural herbaceous vegetation plants are exposed to a vertical light gradient. In experiments, however, morphogenetic responses of stoloniferous plants to shade have nearly always been tested under homogeneous shade conditions. In this study we simulated a vertical light gradient and found that the response of Hydrocotyle vulgaris in this gradient differed considerably from the responses to homogenous shade. Petioles grew longer while at the same time the specific weight of petioles increased. The elongated petioles raised leaf-blades into better-lit places resulting in higher biomass. Though leaves in the light gradient started their growth under low-light conditions, the size of the leaf-blade was the same as in high light. Internodes were longer than in homogeneous shade conditions but specific weight decreased, probably due to increased allocation to the fast-growing petioles. Received: 2 October 1997 / Accepted: 24 July 1998     

李砧木Marianna离体叶片再生体系优化研究

以李砧木‘Marianna’试管苗新梢顶端第1片叶为外植体,研究激素组合、基本培养基种类及外植体类型等对不定芽再生的影响。结果表明:1/2 MS基本培养基和WPM培养基再生率显著高于MS和SH培养基;叶片附带叶柄的外植体再生率和再生不定芽数显著高于叶柄和切除叶柄的叶片外植体;最佳再生培养基为1/2MS+2.0mg/L TDZ+0.1 mg/L IBA+0.25%琼脂+3.0%蔗糖,最高再生率和再生不定芽数分别为81.7%和7.46±1.38个;最佳生根培养基为1/2MS+0.5~1.0 mg/L IBA,能获得96.7%生根率、较高的生根数和根长。     

Floral and growth responses in Chenopodium rubrum L. to an extract from flowering Nicotiana tabacum L.

Flowering of Chenopodium rubrum seedling plants was obtained in continuous light after application of fractions of a partially purified extract from leaves of flowering Maryland Mammoth tobacco (Nicotiana tabacum). The stage of flowal differentiation was dependent on the age of the Chenopodium plants used for the bioassay. Apices of plants treated with the extract at the age of four or seven days showed an advanced branching of the meristem or the beginning of formation of a terminal flower; treatment with the extract of plants 12 d old resulted in rapid formation of flower buds in all assay plants. Non-treated control plants kept in continuous light remained fully vegetative. The effects of the extract on flowering were associated with pronounced growth effects. Floral differentiation was preceeded by elongation of the shoot apex. Extension of all axial organs occurred, while growth of leaves, including leaf primordia, was inhibited. The pattern of growth after application of the flower-inducing substance(s) did not resemble the effects of the known phytohormones, but showed some similarities to growth changes resulting from photoperiodic induction of flowering.     

Changes in soluble carbohydrates during phytochrome-regulated petiole elongation in watermelon seedlings

Changes in soluble carbohydrate composition and concentration in leavesand petioles of watermelon (Citrullus lanatus (Thunb)Matsum and Nakai cv. Sugar Baby) seedlings during early stages ofphytochrome-regulated petiole elongation were investigated. Watermelon seedlingswere grown in a controlled environment with 350 molm^–2 s^–1 photosynthetically activeradiation (PAR) during a 12-h photoperiod. Low intensity end-of-day(EOD) light treatments (for 15 min) of red (R), far-red (FR) and FRfollowed by R (FR/R) were initiated when the seedlings were 14 days old.Seedling growth, and soluble carbohydrate concentration and composition inleaves and petioles were determined after 3 and 6 days of EOD light treatments.The EOD FR increased the petiole length and dry mass partitioned to petioles asearly as 3 days into the treatment. This increased petiole dry mass inFR-treated plants was accompanied with an increase in reducing sugar (glucoseand fructose) concentration in the petioles. Although both leaves and petiolesshowed this effect, the relative increase was greater in petioles than leaves.While the most abundant sugars in petioles were fructose and glucose, thepredominant sugars in leaves were sucrose, raffinose, and stachyose. Thephotoreversion of FR induced changes in growth and sugar concentrations by Rindicates the involvement of phytochrome in these processes.     

Genomic fingerprinting of Frankia strains by PCR-based techniques. Assessment of a primer based on the sequence of 16S rRNA gene of Escherichia coli

Submergence stimulates elongation of the leaves of Rumex palustris and under laboratory conditions the maximum final leaf length (of plants up to 7 weeks old) was obtained within a 9 day period. This elongation response, mainly determined by petiole elongation, depends on the availability of storage compounds and developmental stage of a leaf. A starch accumulating tap root and mature leaves and petioles were found to supply elongating leaves with substrates for polysaccharide synthesis in expanding cell walls. Changes in the composition of cell wall polysaccharides of elongated petioles suggest a substantial cell wall metabolism during cell extension. Reduced starch levels or removal of mature leaves caused a substantial limitation of submerged leaf growth. From the 5th leaf onward enough reserves were available to perform submerged leaf growth from early developmental stages. Very young petioles had a limited capacity to elongate. In slightly older petioles submergence resulted in the longest final leaf lengths and these values gradually decreased when submergence was started at more mature developmental stages. Submerged leaf growth is mainly a matter of petiole elongation in which cell elongation has a concurrent synthesis of xylem elements in the vascular tissue. Mature petioles still elongated (when submerged) by cell and tissue elongation only: the annular tracheary elements stretched enabling up to 70% petiole elongation.     

Photomorphogenesis in Sinningia speciosa, cv. Queen Victoria I. Characterization of Phytochrome Control

The morphological development of Sinningia speciosa plants that were exposed to supplementary far red light was very different from that of plants receiving dark nights. After several nights of such irradiation, stems and petioles were elongated, petioles were angulated, leaf blade expansion was inhibited, plants were chlorotic and the accumulation of shoot dry weight was retarded.

Red reversibility of the morphological changes potentiated by far red light indicated control by the phytochrome system. A high P_FR level during the last half of the night inhibited stem elongation and promoted leaf blade expansion, but both of these processes were hardly affected by the P_FR level during the first half of the night. Thus sensitivity to P_FR was cyclic.

The interpretation of our experiments was complicated by quantitative morphological differences resulting from long, as compared to short, far red irradiations.

     

Effects of Light Spectral Quality on Morphogenesis and Source–Sink Relations in Radish Plants

The accumulation of dry matter and the content of major phytohormones in the aboveground and underground plant parts, as well as light curves and the diurnal course of photosynthesis in the leaves were studied in radish (Raphanus sativusL.) plants of different ages that were grown under red (RL) or blue (BL) light. As seen from the rapid increase in plant biomass, the development of storage organs (hypocotyl or tap root) started on the 14th day after the emergence of seedling of the BL plants and on the 21st day for the RL plants. Conversely, RL stimulated biomass accumulation in the aboveground parts (petioles and stems) already in the early stages of plant development. Light spectral quality only slightly affected the activity and the diurnal course of photosynthesis. The GA content was ten times higher in the aboveground parts of the RL plants than those of the BL plants. The hypocotyl of the BL plants contained much higher amounts of cytokinins and IAA than that of the RL plants. The specific responses of the source–sink relations to the light quality were related to the distribution of various phytohormones between the aboveground and underground parts of the plants: RL increased the content of gibberellins (GA) in the aboveground parts of plants, thus increasing their sink activity, whereas BL stimulated the synthesis of cytokinins and IAA in the hypocotyl and enhanced its development. Light quality-specific morphogenetic responses were reversed when plants were treated with exogenous GA or paclobutrazol, an inhibitor of GA synthesis. The treatment of the BL plants with exogenous GA stimulated petiole and hypocotyl elongation and induced stem formation. The treatment of the BL plants with paclobutrazol led to shortened petioles, the flattening of the storage organ, and the disappearance of the stem.