Dihydroflavonol Reductase Activity in Relation to Differential Anthocyanin Accumulation in Juvenile and Mature Phase Hedera helix L

Juvenile phase English ivy (Hedera helix L.) plants accumulate anthocyanin pigment in the hypodermis of stems and petioles, whereas genetically identical plants of the mature phase do not. The objective of this work was to assess which enzyme(s) might limit anthocyanin accumulation in mature phase ivy. Leaf discs of both juvenile and mature phase ivy accumulated comparable levels of the flavonols kaempferol and quercetin, whereas only juvenile phase discs accumulated anthocyanin. The accumulation of quercetin, but lack of accumulation of leucocyanidin or anthocyanin in mature phase discs, suggested that mature discs lacked dihydroflavonol reductase activity. There was no detectable dihydroflavonol reductase activity in mature phase discs, whereas there was an induction of activity in juvenile phase discs in response to sucrose, or photosynthetically fixed carbon, and light as a photomorphogenic signal. Phenylalanine ammonia-lyase, an enzyme early in the anthocyanin biosynthetic pathway, was induced above its basal level by sucrose and light in discs of both phases of ivy, with greater activity in mature phase discs. Phenylpropanoids, a class of compounds that are precursors to flavonoids, accumulated in leaf discs of both phases, with greater levels in mature phase discs. These results indicate that the lack of dihydroflavonol reductase activity limits the accumulation of anthocyanin in mature phase tissue.     

Polyamines and Adventitious Root Formation in the Juvenile and Mature Phase of English Ivy

The involvement of polyamines during adventitious root formationwas evaluated using a de-bladed petiole rooting assay for theeasy-to-root juvenile and difficult-to-root mature phase ofEnglish ivy (Hedera helix L.). Auxin (NAA 0.1 mM) stimulatedroot formation in juvenile phase cuttings, but failed to promoterooting in the mature phase. The addition of putrescine, spermineor spennidine (1.0 mM) with or without NAA (0.1 mM) did notaffect the rooting response in either the juvenile or maturephase cuttings. There was a significant increase in endogenouslevels of putrescine and spermidine in NAA-treated cuttings,but the only significant difference between the root formingjuvenile and the non-root forming mature phase cuttings wasan increase in putrescine levels. In NAA-treated juvenile cuttings,the polyamine biosynthesis inhibitor DFMA (1.0 mM) promotedroot formation from 9.2 to 14.5 roots per cutting, while DFMO(1.0 mM) reduced root formation from 9.1 to 1.4 roots per cutting.The promotion of rooting by DFMA was completely reversed byputrescine (1.0 mM), but putrescine, spermine or spermidine(1.0 mM) could not reverse the inhibitory effect of DFMO. NeitherDFMA nor DFMO promoted root formation in mature phase cuttings.DFMA was also added to NAA-treated juvenile petioles at variousstages during the root formation process. DFMA promoted rootingwhen applied during the early stages of root induction (0–3d), but became inhibitory to root formation when applied duringthe organization (6–9 d) or root elongation stages (9–12d). Key words: Hedera helix, organogenesis, root initiation, polyamines, DFMA, DFMO     

Ribosomal RNA Gene Redundancy in Juvenile and Mature Ivy (Hedera helix)

Two-fold variation was found in rRNA gene redundancy in differentpopulations of ivy (Hedera helix). No consistent differencein rRNA gene number was observed between the juvenile and matureforms of the plant. Small significant differences between therRNA gene content of mature and juvenile forms and also betweenundeveloped buds and expanded leaves were found but these werein different directions in different populations.     

Phase Change in Hedera helix: Induction of the Mature to Juvenile Phase Change by Gibberellin A3

A sensitive and reproducible method to obtain GA₃ induced morphological reversion of mature Hedera helix to the juvenile form has been developed. Dose response experiments indicate that GA₃ stimulates reversion over a 50–100 fold range with a half maximal response at approximately 0.5 μg GA₃ per plant. The individual characteristics involved in phase change revert to the juvenile form in a sequential manner as GA₃ dose is increased. Variations in light intensity from 1.2–3.6 × 10⁴ lux and temperature from 15 to 26°C do not affect this hormonal response. Other growth regulators including indoleacetic acid, kinetin, abscisic acid and (2-chloroethyl)phosphonic acid (Ethephon) are inactive but other gibberellins (GA₁ and a mixture of A₄–A₇) are active in stimulating reversion. Therefore, the response is specific for gibberellins as a class of hormones but non-specific for a particular form of gibberellin. The significance of this response in relation to juvenility in woody plants is discussed.     

Phase Change in Hedera helix: Stabilization of the Mature Form with Abscisic Acid and Growth Retardants

Applications of ABA to the mature form of Hedera helix stabilize its morphological characteristics and prevent GA₃ induced reversion to the juvenile form. Plants treated with GA₃ reverted to the juvenile form whereas those supplied with ABA in conjunction with GA₃ remained mature. When mature plants were treated with 5 nanomoles of GA₃ and 5 micromoles of ABA, reversion did not occur, but when the GA₃ dose was raised to 25 nanomoles with the same level of ABA, reversion did occur. This implies that the relative amounts of GA₃ and ABA applied are important in controlling growth form and not the absolute levels of these hormones. Applications of growth retardants (Chlormequat, Ancymidol, and SADH) stabilize the mature form by preventing spontaneous reversions induced under low light intensity. These two lines of evidence support the hypothesis that the mature morphological form can be stabilized by regulating the effective level of gibberellins in the plant and this can be accomplished by inhibition of gibberellin action or gibberellin biosynthesis.     

Involvement of the Cotyledon in Adventitious Root Initiation in Impatiens balsamina L. Seedlings

Adventitious root primordia are found in the pre-hypocotyl tissueof developing seeds of Impatiens balsamina L. by the third weekafter petal drop, and are present in the mature seed. Aftergermination, the adventitious roots emerge from a collet swellingon the hypocotyl of the young seedlings. Removal of the colletduring the first five days results in the formation of anotherat the base of the remaining hypocotyl. Older seedlings respondto the excision of the collet by producing one or more rootsnear the cut end, unless the cut is made close to the cotyledon,when, even in nine-day seedlings, a reduced collet is formedassociated with four or fewer roots. The influence of the cotyledonon collet/root regeneration diminishes in older seedlings andin these is manifested only in hypocotyl tissue adjacent tothat organ. Impatiens balsamina, balsam, cotyledon, adventitious roots, collet     

Triterpene saponins from the fruits of Hedera helix

Six triterpene saponins, including two new compounds, were isolated from the fruits of Hedera helix L. (Araliaceae). The structures of the new compounds, named helixosides A and B, were established as 3-O-beta-D-glucopyranosyl-(1-->2)-beta-D-glucopyranosyl hederagenin 28-O-beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranosyl ester, and 3-O-beta-D-glucopyranosyl-(1-->2)-beta-D-glucopyranosyl oleanolic acid 28-O-beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranosyl ester, respectively, on the basis of chemical and spectral data.     

Photosynthesis in frost-hardened and frost-stressed leaves of Hedera helix L.

Abstract The purpose of this study was to determine the respective extents to which winter reduction of photosynthetic capacity in ivy (Hedera helix L.) is caused by direct frost injury to the photosynthetic apparatus and by preceding protoplasmic changes connected with the acquisition of frost tolerance. Potted juvenile ivy plants were placed in the open under natural weather conditions whilst others were hardened under controlled conditions and subjected to the desired frost stress. Low non-freezing temperatures induced frost tolerance in ivy leaves down to about – 12°C (50% injury = TL₅₀) without impairing net photosynthetic rate as measured under standard conditions (20°C, light saturation, natural CO₂ level; = Standard-F_n. Only if the leaves froze (below ? 3°C to ?4°C) was a reversible inhibition of Standard-F_n observed. As long as the temperatures did not fall below approximately ?8°C the inhibition was small and Standard-F_n reached about 80–90% of the control. In this case the stomatal opening narrowed, giving a poorer supply of CO₂ to the mesophyll cells. Maximal frost tolerance (TL_5O?20°C to ?24°C) developed only with severe frosts below about ? 10°C. After such frosts, Standard-F_n was reduced to less than 20% of the control. The dependence of the rate of net photosynthesis on the internal CO₂ concentration showed a lower initial slope, thus indicating disturbances of chloroplast functions. However, neither in outdoor plants nor in those artificially frosted at – 20°C could there be found an appreciable inhibition of the electron transport capacity from H₂O to dichlorophenol indophenol or of ribulose bisphosphate carboxylase. If intact, severely frosted ivy plants were then held at higher temperatures (20/15°C), Standard-F_n recovered completely in approximately 10 d. Furthermore, following a frost period with temperatures down to ?12°C, mild weather caused a distinct improvement in Standard-F_n in outdoor plants, and there was no loss of maximum frost tolerance. Thus it can be concluded that the inhibition of Standard-F_n after severe frosts is not due to the development of maximal frost tolerance, but rather may be attributed to frost damage to the photosynthetic apparatus.     

Proteins in the leaves of different forms of Hedera helix L.

Maturation in Hedera helix involves both quantitative and qualitativechanges in leaf proteins. These changes appear to reside inthe total soluble, globulin and albumin fractions. Senescense,on the other hand, appears to be primarily quantitative withthe greater differenced found in the Kjeldahl and total solublefractions. ¹Contribution from the Missouri Agricultural Experiment StationJournal Paper No. 5745 (Received May 4, 1970; )     

Effect of Auxins on Adventitious Root Development from Single Node Cuttings of Camellia sinensis (L.) Kuntze and Associated Biochemical Changes

An attempt was made to induce rooting from single node cuttings of Camellia sinensis var. TV-20 under controlled conditions and study its biochemical changes during rooting. The nodal cuttings were pretreated with different concentrations of IAA, NAA and IBA and kept in a growth chamber (25 ±2 °C, 16 h photoperiod (55 μ mol m⁻² s⁻¹) with cool, white fluorescent lamps and 65% relative humidity) for 12 h. Among the three auxins used for pretreatment, IBA showed more positive response on rooting as compared to IAA and NAA within 2 weeks of transfer to potting medium. Among four concentrations of IBA tested, 75 ppm gave maximum percentage of rooting, number of roots and root length. Therefore, IBA was used further in experiments for biochemical investigation. The adventitious rooting was obtained in three distinct phases i.e. induction (0–12 days), initiation (12–14 days) and expression (14–18 days). IAA-oxidase activity of IBA-treated cuttings increased slightly as compared to control. The activity was found to decrease during induction and initiation phases and increase during expression phase. The peroxidase activity in IBA-treated cuttings increased up to initiation phase and declined at the expression phase. Polyphenoloxidase activity increased both in IBA-treated and control cuttings during induction and initiation phase but declined slowly during expression phase. Total phenolic content was higher in IBA-treated cuttings, particularly in initiation and expression phases and it also correlated with peroxidase activity. Phenolics might be playing key role for induction of adventitious rooting, and phenolic compounds can be used as rooting enhancer in tea plant.     

A Relationship between Length of Basis and Adventitious Root Formation in Pea Cuttings

A positive correlation between the length of the basis and the ability of the cuttings to form adventitious roots was observed in pea cuttings. Plants with a different basis length (the third internode) were obtained in different ways: Regulation by the level of irradiance, dark treatment or gibberellic acid. The length of the basis was also regulated by excision of the cuttings at different places on the stock plants. With increasing basis length an increase was found in the number of roots subsequently formed. The results were similar in cuttings from plants grown at different levels of irradiance or from dark treated plants. Optimal rooting was obtained by cutting the plants just above the second scale leaf. Cuttings from plants treated with 10^?3M GA₃ showed the same correlation between the length of the third internode and root formation as found in the other experiments, but the number of roots were at a lower level.     

Factors Influencing Adventitious Root Production in Cuttings of Griselinia littoralis and Griselinia lucida

Griselinia littoralis roots quickly and vigorously from cuttingsof seedlings and mature plants and also forms roots on detachedleaves. Cuttings root in the dark but leaves must be present.In contrast G. lucida roots vigorously only from cuttings takenfrom seedlings. Light is essential for root formation on oldermaterial. Detached leaves will not root. Although callus formationat the cut base commonly occurs in both species it is not directlyassociated with root formation. Griselinia littoralis Raoul Choix, Griselinia lucida Forst. f. Prodr., adventitious roots, stem cuttings, leaf cuttings, woody plants     

Water Pathways in Leaves of Hedera helix L. and Tradescantia virginiana L.

Hydraulic conductances of leaf tissues of Hedera helix and Tradescantiavirginiana leaves were measured. It was found that water couldflow most easily through the veins, but that the cell wallsof at least the ventral epidermis were more efficient at resupplyingwater lost from the epidermal tissue than was the mesophyllat rehydrating itself. Vein and bundle-sheath extensions, whichare characteristic of mesomorphic leaves (e.g. T. virginiana),seem to be important in maintaining a close hydraulic connectionbetween the epidermis and the vascular tissue. In leaves notcontaining vein and bundle-sheath extensions, typically xeromorphicleaves (e.g. H. helix), there is not such a close connectionbetween the epidermis and vascular tissue. This was shown inexperiments involving the sudden application of a reduced pressurepotential to either the epidermis or the other tissues of leaves,and the measurement of transient stomatal opening.     

Cuticular waxes from ivy leaves (Hedera helix L.): analysis of high-molecular-weight esters

Soluble waxes were extracted from the cuticle of ivy (Hedera helix L.) leaves with dichloromethane in a yield of ca. 13%. The cuticular waxes were directly analysed by GC-MS, high-temperature GC-MS and ESI-MS/MS. The GC-MS analysis showed mostly n-alkanols (45.3%), monoacids (18.8%), triterpenes (9.7%), n-aldehydes (8.7%) and n-alkanes (7.7%). The high-temperature GC-MS and the ESI-MS/MS analyses showed the presence of ester waxes, namely alkyl alkanoates and alkyl coumarates. Alkyl alkanoates comprised esters of the hexadecanoic acid with n-alkanols ranging from C16 to C34. Alkyl coumarates included esters of coumaric acid with n-alkanols ranging from C16 to C32. The cuticular waxes were hydrolysed and the resulting organic and aqueous phases analysed by GC-MS. The hydrolysate showed a major increase in the quantities of n-alkanols, hexadecanoic acid and coumaric acid derived from the alkyl and acyl moieties from the ester waxes. A content of ester waxes of 38% was estimated based on the results from the GC-MS analysis of the non-hydrolysed and hydrolysed cuticular waxes. Alkyl alkanoates were analysed by ESI-MS/MS as [M + Li]+ adduct ions and the alkyl coumarates as [M - H]- deprotonated ions. The ESI-MS/MS analysis allowed the detection of a wider range of ester waxes than high-temperature GC-MS, and was shown to be a useful technique for the qualitative analysis of ester waxes from plant cuticles.     

Gonadotropin Promotion of Adventitious Root Production on Cuttings of Begonia semperflorens and Vitis vinifera

Adventitious rooting of Begonia semperflorens cv. Indian Maid and Vitis vinifera cv. Semillon stem cuttings was significantly promoted by human chorionic gonadotropin (HCG). Basal sections of HCG treated cuttings upon which promoted rooting took place had markedly less endogenous gibberellin (GA) activity than non-treated controls or apical sections of treated ones, while changes in auxin levels were not found. HCG also inhibited GA(3)-induced reducing sugar release from embryoless barley endosperm halves. These findings are discussed in the light of a possible analogy to gonadotropin action in animal systems.     

The Anatomy of Root Initiation in Cuttings of Griselinia littoralis and Griselinia lucida

The initiation of root primordia in Griselinia littoralis andG. lucida occurred a few millimeters above the cut base. Inall cases the first cellular event was the activation of specificregions of the cambium which were associated with traces fromleaves which themselves were particularly vigorous root-formersif detached. In cuttings from seedlings, the first cells cutoff continued to divide and gave rise to root primordia in situ,whereas those from mature plants produced files of six to 22rows of cells and it was only when the cells first cut off hadbeen displaced outwards towards the fibre caps that the cambiumstopped dividing. Primordium development may then occur at theadvancing front, possibly as a result of a stimulus originatingfrom damaged cells. Thus the same cells were involved in organizedprimordium formation both in seedling and mature cutting, butthe location differed. The reduced rooting and the long lag phase in cuttings frommature plants of G. lucida may be due to the presence of a completering of fibres. This does not seem to present a mechanical barrierto emergence - since elongating primordia can force throughthe ring - nor can it affect the receipt of any root-inducingstimulus by the target cells since it is considered that thisarrives via the vascular tissues. However, evidence suggeststhat it is the initial phase of cambial activation which isprevented in cuttings from mature plants. This suggested eitherthat the initial stimulus was less effective or that the targetcells were less responsive than those of seedlings, which havevery few fibres, or of mature G. littoralis, which only hasfibm associated with the vascular bundles. Griselinia littoralis Raoul Choix, Griselinia licida Forst. f. Prodr., adventitious roots, cuttings, primordium initiation and location     

Mixed culture of micro-organisms in the rhizosphere of ivy (Hedera helix L.)

Summary The development ofAzotobacter chroococcum is promoted in the ivy (Hedera helix L.) rhizosphere when it is colonized by the pectinolytic moldMucor fragilis. The multiplication of Azotobacter cells in the mineral solution of ivy cultures induces a decrease of the amount of sugars excreted by the roots and a increase of the amount of nitrogen. Within the experimental period Azotobacter does not influence the growth of ivy roots although it seems to be promoted by Mucor. Filtrates of Mucor culture are, however, harmful to the plant.