Metabolic changes during adventitious root primordium development in <Emphasis Type="Italic">Tectona grandis</Emphasis> Linn. f. (teak) cuttings as affected by age of donor plants and auxin (IBA and NAA) treatment

Aging of the donor tree decreased adventitious root formation in shoot cuttings of Tectona grandis Linn. f. (teak). Exogenous application of auxins, i.e., α-naphthalene acetic acid (NAA) and indole-3-butyric acid (IBA) has a significant positive effect on the percentage of rooting. The maximum percent rooting was obtained with 4,000 ppm IBA as compared to other treatment. Significant increase in root number was recorded in shoot cuttings treated with 4,000 ppm NAA. The overall rooting response was better in the treatment with IBA rather than with NAA. Further periodic samples (0, 10, 20, and 30 days) were taken to assess the total soluble sugar, starch, protein, and peroxidase (PER) activity in the rooting zone of shoot cuttings of teak during adventitious root formation. Application NAA and IBA to shoot cuttings resulted in an increase in the level of total soluble sugar, starch, protein, and PER-activity in the rooting zone. The stored carbohydrates were utilized during adventitious root formation. Hence, total soluble sugar and starch contents of cuttings, irrespective of age of donor plants, decreased with the passage of time in cuttings planted for rooting. Significant fluctuations were observed in the protein content of cuttings during the time of root induction. There was an increase in the protein content with the passage of time from the day of planting up to its 20th day, followed by a sharp decline in the protein content of cuttings at the 30th day of planting, irrespective of the age of donor plants or the treatment of cuttings with auxins. Irrespective of donor plant age, PER-activity in the cuttings increased from the day of their planting for rooting up to the 20th day, and then declined at its 30th day of planting. It was interesting to note that PER-activity remained higher at all stages in the cuttings of 2-month-old seedlings which rooted profusely as compared to the cuttings of 15- and 30-year-old donor plants those rooted poorly. This study suggested that the exogenously applied NAA and IBA at different concentration seems to activate sugar metabolism for release of energy, protein and PER-activity which are necessary for cellular division and differentiation during adventitious root primordium initiation or development in the rooting zone of shoot cuttings.     

Vegetative propagation of Colutea arborescens L., a multipurpose leguminous shrub of semiarid climates

The vegetative propagation of the multipurpose leguminous shrub Colutea arborescens from leafless hardwood cuttings was examined. Specific attention was paid to the factors: 1) cutting origin (apical, medial or basal); 2) indole-3-butyric acid (IBA) treatment (0, 50 or 200 ppm); and 3) relative humidity of the propagation environment (high or low humidity). After 120 days, 67.6% of the C. arborescens cuttings had rooted. The rooting ability of the cuttings was significantly influenced by the cutting origin and hormonal treatment. No effects on rooting percentage were shown by the relative humidity of the propagation environment. The best rooting response (95%) was shown by basal cuttings treated with 200 ppm IBA. Cutting origin, IBA treatment and relative humidity were significantly related to the root number, longest root length and the fresh/dry biomass of roots and leaves. Under conditions of high humidity, basal cuttings treated with 200 ppm IBA gave rise to the most highly developed plants. The positive relationship between sprouting and rooting suggests that successful propagation is related to the shoot formation potential of the cutting's food reserves. These findings were used to propose an efficient method for the vegetative propagation of C. arborescens plants. This revised version was published online in June 2006 with corrections to the Cover Date.     

Indole-3-butyric acid accelerates adventitious root formation and impedes shoot growth of Pinus elliottii var. elliottii?×?P. caribaea var. hondurensis cuttings

Many plantation tree species are cloned to achieve the growth, disease resistance and wood quality characteristics required for a successful economic venture. However, clonal propagation is limited by declines in adventitious root formation with increasing stock plant age. We examined the effects of immediate or delayed IBA application on adventitious root formation and subsequent root and shoot development of cuttings harvested from 8-year-old clonal hedge plants of Pinus elliottii var. elliottii × P. caribaea var. hondurensis. IBA applied at the time of setting accelerated root formation, elevating the percentage of cuttings with roots at 13 weeks post-setting from 45 to 78% and from 83 to 93% for a low- and a high-rooting clone, respectively. Final rooting percentages for the same treatments and clones (78 and 85%, and 88 and 100%, respectively, at 20 weeks post-setting) were not significantly affected by IBA application. IBA increased the root:shoot ratio of rooted cuttings by decreasing shoot weight compared with untreated cuttings, without affecting root weight, root length, root surface area or root volume. IBA was only effective when applied at the time of setting. A simple IBA treatment for cuttings from 8-year-old clonal hedges, by accelerating root production, has potential for reducing nursery costs and increasing the root system quality of containerised pine cuttings.     

Rooting of baldcypress cuttings

A test of the rooting performance and growth of cuttings from 1-year-old and 25-to 50-year old baldcypress (Taxodium distichum L.) branch tips is reported. Rooting of cuttings from one-year-old trees averaged 75% (0.1% IBA treatment) and 88% (control), cuttings from 25 to 50-year-old trees averaged 12% in both the IBA treatment and the control treatment. Indole-3-butyric acid at a 0.1% concentration did not enhance rooting, but resulted in a significant increase in shoot dry weight on cuttings from one-year-old trees. The results of this experiment suggest that cuttings from mature baldcypres trees have the potential to root, thereby, additional rooting techniques such as girdling and stump sprouts is worthy of pursuing.     

Drought tolerance, growth partitioning and vigor in eucalypt seedlings and rooted cuttings

To clarify the physiological basis of productivity differences among rooted cuttings and seedlings of eucalypt species, relationships between morphology and water relations were examined in 4-month-old seedlings of Eucalyptus grandis W. Hill ex Maiden, E. urophylla S.T. Blake and E. cloeziana F. Muell. and in 4-month-old rooted cuttings of three E. grandis cultivars. Four-month-old seedlings had greater dry weights, lower leaf area/root dry weight (LA/RDW) ratios and lower shoot/root dry weight (S/R) ratios than 4-month-old rooted cuttings. For all cultivars of E. grandis, tall rooted cuttings, as defined by height at age 4 weeks, had greater dry weights by age 4 months and lower LA/RDW and S/R ratios than short rooted cuttings. There were differences in height growth, dry matter productivity and relative shoot and root development among cuttings of different E. grandis cultivars, but these differences were not as great as the differences between short and tall grades of the same cultivar and between seedlings and cuttings. Consistent with the differences in LA/RDW and S/R ratios, seedlings had higher daytime water potentials (Psi(x)) than cuttings, and tall cuttings had higher daytime values of Psi(x) than short cuttings. Differences in Psi(x) were also related to stomatal conductance (g(wv)), which was up to 300% greater in short cuttings than in tall cuttings. Among seedlings, those of E. cloeziana, which had the smallest dry weight at age 4 months, had the highest g(wv), whereas those of E. grandis, which had the greatest dry weight at age 4 months, had the lowest g(wv). Unlike seedlings and the tall cuttings, short cuttings lost turgor when subjected to drought. The differences observed in susceptibility to water stress may account in part for the associated differences in dry matter production. Xylem pressure potential and relative water deficit at zero turgor did not differ significantly among the types of plants studied, which suggests that differences in growth rates were not the result of differences in dehydration tolerance.     

IBA和PP_(333)对乌桕扦插生根的作用

用IBA500ppm和1000ppm酒精溶液处理乌桕嫩枝扦插条,能促进插条生根及生长。用500 ppm和1000ppm PP333溶液处理插条,扦插后的前20天表现出对生根有不同程度的抑制作用。但40天时,500 ppm处理的生根率明显增高,1000ppm处理的也出现了愈伤组织,并表明其对根的粗度生长具有促进作用。     

Adventitious rooting in shoot cuttings of Azadirachta indica and Pongamia pinnata

Adventitious rooting in shoot cuttings of neem (Azadirachta indica) and karanj (Pongamia pinnata) was investigated in different seasons. The influence of auxins and B-vitamins (neem only) was evaluated. Maximum rhizogenesis coincided with the emergence of new sprouts i.e. February (neem) and March (karanj). Considering both rooting percentage and root biomass, IBA was the most effective auxin tested. Compared to auxin free controls, IBA (1000 ppm in neem and 800 ppm in karanj) significantly increased adventitious rooting percentage (80 to 100 % respectively), the numbers of roots and root biomass for both species. In neem, B-vitamin treatment yielded 40–50% rooting for cuttings. This was significantly greater than rooting for controls but equivalent to IAA treatments. In neem, some of the cuttings treated with 2000–3000 ppm IBA had well developed root systems without any sprouts. In karanj, all auxin treatments promoted sprouting. The level of total soluble sugars in the rooting zone of neem and karanj was higher in non-rooted than rooted cuttings.     

Vegetative propagation of Ulmus villosa: effects of plant growth regulators,collection time,type of donor and position of shoot on adventitious root formation in stem cuttings

Techniques for the vegetative propagation of Ulmus villosa, an indigenous agroforestry tree species of the north-western sub-Himalayas, were developed. Studies investigated the effects on rooting of stem cuttings of growth regulators with sucrose and fungicide (0%, 0.2% p-HBA + 5% sucrose + 5% captan, and IBA concentrations ranging from 0.2 to 1.0% plus each containing, 0.2% p-HBA + 5% sucrose + 5% captan). Cuttings were collected at two times of the year (February and July) from two types of stock plant (seedling and mature trees) and from two positions within the shoots (lower and upper nodes). Cuttings collected in February were leafless, while those collected in July had about 80 cm² leaf areas. These cuttings were then set under a mist unit. Percentage rooting and primary root number differed significantly between treated and untreated cuttings. Treatment of cuttings with chemical formulations of 0.4% IBA + 0.2% p-HBA + 5% sucrose + 5% captan maximized rooting (82.0%), while, survival (80%) and primary root number (14.7) were greatest with: (i) 0.6% IBA + 0.2% p-HBA + 5% sucrose + 5% captain and (ii) 0.8% IBA + 0.2% p-HBA + 5% sucrose + 5% captan, respectively. Rooting success and root number were better in propagules set in February rather than in July. Cuttings from seedlings rooted better, with more roots ensuring better survival, than cuttings from mature trees (12–13-years-old). In cuttings from seedlings, those cuttings collected from the lower part of the shoots had greater percentage rooting and primary root number than those from the upper part. Maximum root regeneration (100%), roots number (19.0), and survival (98.5%) were achieved when the time of collection (February) and shoot position were optimized. Rooting was best when cuttings had higher levels of sugar, total carbohydrate and peroxidase enzyme activity, and low N.     

Configuration and development of root systems of cuttings and seedlings of Eucalyptus globulus

Stem cuttings of Eucalyptus globulus are used within tree improvement programs and for mass deployment. To be successful, cuttings must perform as well or better than seedlings. The root systems of cuttings are fundamentally different from those of seedlings. If these differences influence growth, the differences and their consequences must be identified and the propagation system manipulated to improve performance of the propagules.Cuttings are only a viable alternative to seedlings as planting stock if the method of propagation does not affect their growth and development adversely. Full-sibling cuttings and seedlings of Eucalyptus globulus were compared under controlled environmental conditions to minimise extraneous sources of variation, and to establish whether changes in growth or development were induced by propagation. On three occasions over a period of eight weeks root-collar diameter, shoot height, leaf and stem weight, shoot/root ratios and root system morphology were measured on cuttings and seedlings. Seedlings were taller than cuttings throughout the experiment, but both plant types had similar height growth rates. Diameter growth rates were lower in cuttings than seedlings, and there were differences in both height and diameter growth rates between families. Root system configuration differed between the plant types. Seedlings had strongly gravitropic tap-roots, with two types of primary roots from which secondary roots emerged. Cuttings had no tap roots, and the main structural components of their root systems were adventitious roots formed during propagation. Cuttings did not develop further structural roots during the experiment, whereas seedlings continued to develop primary roots. Individual primary roots of cuttings were longer and had larger mid-point diameters than those of seedlings, but the total length of primary roots was greater in seedlings. Seedlings also had a greater number and total length of secondary roots. Shoot/root ratios, calculated from a range of functional measures, were higher in cuttings than seedlings.     

A Note on the Dimensions of Shoots and Roots of Planting Stock

Published figures suggest that in Pinus and Picea spp. plantingstock raised in nurseries the top/root ratio increases fromthe first year onwards. Transplanting checks growth in heightthe more severely the longer the time that has elapsed sincethe last transplantation, but growth in weight and diameteris much less affected, so that the shoot of a transplant isstouter and heavier than that of a seedling of the same height.On the other hand, growth of the root, both in length and weight,is encouraged, so that the top/root ratio of a transplant ismuch less than that of a seedling of the same age. In seedlings of broadleaved trees top/root ratio is less thanin Pinus and Picea, and usually decreases for 2 or 3 years. The top/root ratio and dimensions of the plants are also subjectto some individual variation which might be either inherentor due to external circumstances, including espacement. Informationon such variation is too scanty and inconsistent to supportany generalizations, except that diameter of shoot increaseswith increasing espacement.     

Clonal propagation of <Emphasis Type="Italic">Dalbergia sissoo</Emphasis> Roxb. and associated metabolic changes during adventitious root primordium development

A study was conducted on the twelve clones of shisham (Dalbergia sissoo Roxb.). These clones were obtained from India and Nepal. Single-node leafy cuttings were prepared from the vegetative multiplication garden to examine the clonal variation, effect of IBA treatment on rooting response and associated metabolic changes during adventitious root formation. A remarkable and significant variation was observed due to treatment of 2,000 ppm IBA in the rooting parameters. Clonal variations were also significant for root and shoot growth while length of root was insignificant. Among the twelve clones studied; C3 (Tulsipur, Gonda, Uttar Pradesh, India) and C4 (Laxmipur, Gonda, Uttar Pradesh, India) clone cuttings have given the highest rooting response. Interaction (clone × IBA) was significant only for production of number of roots per cutting. Periodic sampling for clone C3 was performed at 0, 7, 14, 21, 28 and 35 days to examine the contents of total soluble sugars, starch, protein and peroxidase (PER) activity in the rooting zone of cuttings (∼0.5 cm) during adventitious root primordium development. A significant increase in all the metabolic activities was noted due to IBA. Total soluble sugars and starch contents of cuttings decreased with the passage of time. Protein content and PER-activity started to increase in the early stage and reached the highest level on day 21, followed by a decline at the 35th day of sampling. These trends were common for both IBA treated and untreated cuttings. Protein content and PER-activity remained higher in the rooting zone of IBA treated cuttings. Overall these findings suggested that exogenous application of IBA may have activated carbohydrate metabolism for release of energy, while protein and PER-activity were necessary for cell division and differentiation during adventitious root primordium initiation and development in the rooting zone of cuttings.     

Auxin-impregnated hygroscopic gel: effects on ponderosa pine and common hackberry seedlings

Greenhouse and field studies were conducted to determine the effects of indole3-butyric acid (IBA) and 2,4-dichlorophenoxyacetic acid (2,4-D) on root development and survival of 3+0 bareroot Pinus ponderosa (Dougl. ex Laws.) and 2+0 bareroot Celtis occidentalis (L) seedlings. In the greenhouse, 100 and 200 ppm. IBA and 10 and 50 ppm 2,4-D were applied to seedlings through a root dip in an auxin hygroscopic gel mix. A randomized complete block analysis of variance indicated that IBA gel treatments increased root volume and root dry weight in hackberry and had no effect on ponderosa pine; 2,4-D gel treatments had detrimental effects on both species. In the field, IBA gel treated ponderosa pine seedlings exhibited improved height and survival relative to the non-treated control seedlings. There was no detectable improvement in survival in the field for hackberry. However, diameter and stem dry weight were lower for hackberry seedlings treated with the gel dip alone.     

Adventitious roots, leaf abscission and nutrient status of flooded Gmelina and Tectona seedlings

When flooded, seedlings of Gmelina arborea Roxb. produced more adventitious roots, had lower foliar Mn concentrations and lost fewer leaves than seedlings of Tectona grandis L.f. Severing the adventitious roots produced by flooded Gmelina seedlings increased leaf Mn concentration and leaf abscission and reduced whole-plant dry matter production. Flooded Gmelina cuttings, which do not produce adventitious roots, abscised few leaves until foliar concentrations of Mn and Fe had risen substantially above those of unflooded cuttings, at which time most leaves were shed. The results indicate that the development of adventitious roots in flooded seedlings of Gmelina suppressed uptake of Mn thereby minimizing leaf abscission.     

Effects of IBA on the rooting of branch cuttings of Chinese jujube (<Emphasis Type="Italic">Zizyphus jujuba</Emphasis> Mill.) and changes to nutrients and endogenous hormones

‘Zhongqiusucui’ jujube secondary shoots were treated with 3-indolebutyric acid (IBA) at three concentrations, 500, 1000 and 1500 mg/L. Results show that IBA could significantly enhance rooting and root characteristics of cuttings and were best with IBA at 1500 mg/L. In the rooting process, the formation of adventitious roots was related to the consumption and accumulation of nutrients (soluble sugars and proteins) and the changes in endogenous hormones in phloem, leaf tips and leaf bases. The rooting of cuttings had a positive correlation with the consumption of soluble sugars during the period of callus formation and with the accumulation of soluble sugars during adventitious root formation and growth. Rooting was positively related to the breakdown of soluble proteins in the phloem when the callus formed, and had a positive correlation with its accumulation during adventitious root formation and growth. Leaf tips and leaf bases showed a reverse trend in changes of soluble protein. However, together with the phloem, leaf tips and leaf bases regulated and controlled the formation and development of adventitious roots. The main activities of soluble proteins exist in the leaf tips as this was the main source of soluble proteins. The relation between rooting and IAA (indole-3-acetic acid) content in phloem was positive and thus a high concentration of IAA could benefit the induction and formation of adventitious roots. However, rooting was negatively related with ABA (abscisic acid) and GA (gibberellic acid) and a high concentration of both could inhibit the induction and formation of adventitious roots. Rooting had a positive correlation with phloem IAA/ABA ratios, and higher ratios could improve rooting. Low concentrations of ZR (zeatin riboside) triggered the induction of adventitious roots, while higher concentrations promoted root growth. Endogenous hormones in leaf tips and bases had an impact on rooting. The activities of endogenous hormones mainly existed in leaf tips because they play a major role in the production and consumption of IAA and its ABA content increased during rooting. The ZR in leaf tips influenced the rooting of cuttings, especially in the callus formation and rooting stage. Leaf tips were the main source of GA.     

Growth of Eucalyptus marginata (Jarrah) seedlings in a greenhouse in response to shade and soil temperature

The effects of shade and soil temperature on growth of Eucalyptus marginata Donn ex Sm (jarrah) seedlings were studied in greenhouse experiments. Plant dry weight and that of all plant parts declined in response to shade, as did root/shoot ratio. Plant leaf area was less in unshaded plants than in plants grown in shade, and specific leaf area increased with shade. Unshaded seedlings had a higher light-saturated rate of photosynthesis, a higher light compensation point and a higher light saturation point than seedlings grown in 70% shade. The relationship between plant dry weight and leaf dry weight was independent of shading, whereas the relationship between plant dry weight and plant leaf area was dependent on shading. Therefore, leaf dry weight may be a better predictor of biomass production than leaf area in forest stands where shade is likely to affect growth significantly. Soil temperature had a significant effect on the growth of all plant parts except cotyledons. Total plant growth and shoot growth were maximal at a soil temperature of 30 degrees C, but root growth had a slightly lower temperature optimum such that the root/shoot ratio was highest at 20 degrees C. Roots grown at 15 degrees C were about 30% shorter per unit of dry weight than roots grown at 20 to 35 degrees C. We conclude that increases in irradiance and soil temperature as a result of overstory removal in the forest will cause significant increases in growth of E. marginata seedlings, but these increases represent a relatively small component of the growth response to overstory removal.     

Root initiation of Shorea macrophylla cuttings: Effects of node position,growth regulators and misting regime

Single-node leafy cuttings from 8- and 15-month-old seedlings of the large Bornean Dipterocarp Shorea macrophylla (Illipe nut) rooted easily under continuous mist, both with and without the application of auxins. Callus production was greatest in the untreated cuttings. Rate of rooting was enhaced by 1200 ppm and 3600 ppm IBA, but the overall level of rooting after 61 days was unaffected by auxin treatment. In a second experiment, 3600 ppm IBA was found to be more effective than 3600 ppm NAA and mixtures of 1800 ppm NAA + 1800 ppm IBA. Mortality of cuttings was greatest with IBA especially at 10800 ppm. Cuttings from the second node below the apex rooted best, with rooting ability of those from nodes 3, 4 and 5 being progressively worse, and mortalities rising with distance from the apex. Cuttings from the uppermost node, which included the developing apex, had the lowest rooting ability. When continuous misting was replaced with misting for alternate hours, rooting was still good, but the absence of misting overnight resulted in much increased cutting mortality and, subsequently, in decreased rooting. It is suggested that Shorea macrophylla could be domesticated for fruit or timber production by the propagation of superior clones.     

Vegetative propagation of Aesculus indica through stem cuttings treated with plant growth regulators

Cuttage propagation of Aesculus indica was tested by treatments with different concentrations of indole-3-acetic acid (IAA) @ 2000, 4000 (ppm), indolebutyric acid (IBA) @ 2000, 4000 (ppm) and naphthlcetic acid (NAA) @ 2000, 4000 (ppm) in dry formulation in the Forest Nursery, Faculty of Forestry, SKUAST-K, Shalimar. The cuttings treated with IBA @ 4000 ppm and IBA @ 2000 ppm had a sprouting rate of 75% and 50%, respectively, which was significantly higher than that of control and other treatments. The highest rooting rate (50%) was recorded in the cuttings with the application of IBA @ 4000 ppm. The cuttings treated with IBA @ 2000 ppm had 25% rooting rate. All other treatments along with control (talc powder) failed to induce rooting. It was concluded that IBA @ 4000 ppm was a better-applied concentration for vegetative propagation of A. indica under Kashmir conditions. Biography: Mumtaz Majeed (1980– ), male, post graduate in Faculty of Forestry, Sher-e-Kashmir University of Agricultural Science & Technology, Shalimar, Srinagar - 191 121, J&K, India.     

Effect of branch position and auxin treatment on clonal propagation of <Emphasis Type="Italic">Tectona grandis</Emphasis> Linn. f.

The main objective of our clonal propagation program is the production of high quality timber and faster tree growth. Teak (Tectona grandis Linn. f.) is an important plantation species in the tropics but the demand of teak timber is increasing globally. Teak planting stock is still produced from seeds of unselected elite genotypes which may lead to poor stand establishment. The number of seeds per fruit and their germination ability are also variable and limited by several factors. Therefore an alternative method i.e., clonal propagation is required for mass multiplication of elite trees. It is an established fact that the clonal propagation or adventitious root formation in cuttings is markedly affected by several external and internal factors. Considering these, an experiment was conducted on leafy soft wood shoot cuttings of 3-year-old hedged teak stock plants grown in a hedge garden to study the effects of branch position and auxin treatment on adventitious root formation. A factorial completely randomized design was used for experimentation. Coppice shoots were collected from basal, middle and upper positions of the hedge garden; and mono-nodal leafy cuttings were prepared. These cuttings were treated with different concentrations of IBA and NAA; and were cultured in a mist chamber for rooting where the relative humidity was maintained at 85 ± 2% with maximum and minimum day-night temperature at 32 ± 1°C and 26 ± 1°C respectively. After 45 days the cuttings were removed from the rooting medium and observations were made. It was observed that the rooting parameters viz., percent rooting and percent sprouting, mean number of leaves, mean number of shoots and length, and mean number of roots and length per cutting were significantly influenced by the branch position and auxin treatment. Treatment with 4000 ppm IBA increased percent rooting and percent sprouting whereas NAA suppressed it. Treatment with 4000 ppm IBA also increased the mean number of leaves and shoots, and the length, and the mean number of roots per cutting. The highest mean number of roots and length were observed in cuttings taken from the branch emerging at the upper position followed by branches of middle and lower position. Cuttings of branches at a middle position showed the highest values of percent rooting, percent sprouting, mean number of leaves and shoots and mean shoot length per cutting. Furthermore, the interactive effect of branch position and auxin treatment on rooting and sprouting response was also found to be significant. Overall, the findings of this investigation suggest that middle branch position in hedge plants and 4000 ppm IBA can be made to induce maximum rooting and to produce high quality planting stock material for clonal forestry program of teak.     

Cutting propagation of <Emphasis Type="Italic">Santalum austrocaledonicum</Emphasis>: the effect of genotype,cutting source,cutting size,propagation medium,IBA and irradiance

Developing methods for routine clonal propagation of sandalwood (Santalum austrocaledonicum) is important for its domestication and development as a commercial agroforestry species. The amenability of this species to propagation by leafy stem cuttings in low-cost non-mist propagators was assessed in four separate experiments. These experiments evaluated the effects of (1) genotype (15 genotypes from two island provenances), (2) cutting position on the stock plant (apical, medial and basal), (3) cutting size (1-node/400 mm² and 2-node/800 mm² leaf area), (4) three propagation media [scoria (5 mm, air-filled porosity (AFP)—29%), vermiculite and perlite (1:1 v/v, AFP—46%) and vermiculite, perlite and peat (2:2:1 v/v/v, AFP—42%)], (5) indole-3-butyric (IBA) (3000, 4000 and 8000 ppm) and (6) irradiance in the propagator [daily light integral (DLI) 5.3, 3.9, 2.6, 2.2 mol m^?2 day^?1]. IBA, propagation media and cutting size had no significant effect on rooting percentage, root number or root growth. Evidence of provenance-based variation in rooting capacity was recorded with greater rooting success for genotypes from the island of Erromango compared with Tanna. Variation in adventitious root induction was also recorded between individual genotypes from Erromango across all four experiments. Cuttings collected from the apical and medial parts of the shoot on the stock plant had higher rooting percentage than those collected from the base. Differences in rooting capacity between apical and medial shoots were variable between experiments and may be attributed to different levels of hardening. The use of artificial shade (~?70%) to achieve a mean DLI of between 2.6 and 3.9 mol m^?2 day^?1 increased rooting percentage compared to both lower (2.2 mol m^?2 day^?1 or?~?90% shade) and higher (5.3 mol m^?2 day^?1 or?~?50% shade) irradiance treatments. Leaf retention of cuttings in the propagator was positively associated with the percentage of cuttings with adventitious roots, with highest percentage in cuttings with full leaf retention, regardless of original cutting size. This study demonstrated S. austrocaledonicum seedlings can be successfully propagated by cuttings provided the propagation conditions are optimized for each genotype.     

连香树嫩枝扦插繁殖技术研究

以连香树(Cercidiphyllum japonicum)当年生枝条为材料,研究了不同植物生长调节剂、不同IBA浓度及其处理时间对插穗生根的影响。结果表明:连香树属于皮部生根型,只有极少数为愈伤组织生根。植物生长调节剂处理是提高嫩枝插穗生根能力的一个必要措施,其中IBA对连香树插条生根效果最好,NAA次之,IAA最差。采用IBA 100 mg.L-1+NAA 100mg.L-1混合处理嫩枝插条效果最好,生根率达到81.67%,且幼苗长势良好。IBA 500 mg.L-1快蘸处理8 s,生根率达到71.67%;IBA 200 mg.L-1浸泡6 h,生根率为77.78%。综合各项生根指标,采用IBA 100 mg.L-1+NAA 100 mg.L-1浸泡嫩枝插条4 h,最适宜连香树插条生根。