Number Of New Shoots Research Articles

Growth and fruit production of asian pear trees grown on Y-, T-, and vase-training systems

This study was carried out to evaluate the effects of training systems on growth and fruit production of ‘Niitaka’ pear (Pyrus pyrifolia L.) trees in the first 8 years in South Korea. The training systems included Y-trellis (YT), T-trellis (TT), and vase-pergola with either two (VP I) or three main branches (VP II). Tree spacing for YT, TT, VP I, and VP II were 6.5 m between tree rows, and 3.0, 6.0, 3.0, and 6.5 m between trees, respectively. The TT trees had lower tree height, canopy area, and number of new shoots, average length of new shoots, and trunk cross sectional area as compared to those in other training systems in year 3 or year 8. The TT and VP II systems were slow to fill the allotted space from year 3 to 8. The VP I trees had comparatively rapid development of the tree canopy, high cumulative yield efficiency per tree, high cumulative fruit yield per area, and large fruit size, as well as low operation hours for orchard management. Fruit quality parameters, such as fruit shape, soluble solids content, firmness, and titratable acidity, were not consistently affected by training system in years 5 and 8.

Elucidating the Population Dynamics of Japanese Knotweed Using Integral Projection Models

Plant demographic studies coupled with population modeling are crucial components of invasive plant management because they inform managers when in a plant’s life cycle it is most susceptible to control efforts. Providing land managers with appropriate data can be especially challenging when there is limited data on potentially important transitions that occur belowground. For 2 years, we monitored 4 clonal Japanese knotweed ( Polygonum cuspidatum ) infestations for emergence, survival, shoot height until leaf senescence, dry shoot biomass after senescence, and rhizome connections for 424 shoots. We developed an integral projection model using both final autumn shoot height and shoot biomass as predictors of survival between years, growth from year to year, and number of rhizomes produced by a shoot (fecundity). Numbers of new shoots within an infestation (population growth rate λ) were projected to increase 13-233% in a year, with the greatest increase at the most frequently disturbed site. Elasticity analysis revealed population growth at 3 of the 4 sites was primarily due to ramet survival between years and to year-to-year growth in shoot height and shoot biomass. Population growth at the fourth site, the most disturbed, was due to the large production of new rhizomes and associated shoots. In contrast to previous studies, our excavation revealed that most of the shoots were not interconnected, suggesting rhizome production may be limited by the size or age of the plants, resource availability, disturbance frequency, or other factors. Future integration of plant population models with more data on belowground growth structures will clarify the critical stages in Japanese knotweed life cycle and support land managers in their management decisions.

Improving an in vitro propagation protocol for Cestrum nocturnum L.

The present study was carried out to assess the micropropagation of <em>Cestrum </em>(<em>Cestrum nocturnum<strong> </strong></em>L.) by using single nodes and shoot tips excised from soft cuttings using MS salts, 30 g × l<sup>-1</sup> sucrose, 7 g × l<sup>-1</sup> agar, and different concentrations of plant growth regulators in culture medium.<strong> </strong>The results revealed that the use of mercuric chloride (0.05%, HgCl<sub>2</sub>) for 7 minutes was very effective in preventing contamination and gave the highest survival percentage (99%). The highest response (100%) was gained at initiation stage from lateral bud explants on MS medium supplemented with 1.5 mg × l<sup>-1</sup> of BA with most of NAA concentrations. However, in case of terminal buds, higher percentages of responses were resulted from the interaction of BA (1.5 mg × l<sup>-1</sup>) with 0.2 mg × l<sup>-1</sup> NAA. The lateral buds also produced more new shoots as well as a higher number of leaves and length of new shoots on the medium supplemented with 1.5 mg × l<sup>-1</sup> BA as compared with those from terminal buds. Significant differences were observed at multiplication stage between the lateral buds and terminal buds, since the lateral buds produced a higher number of new shoots and leaves as well as longer new shoots. At rooting stage, the treatment with 1 mg × l<sup>-1</sup> IBA gave the highest percentage of rooting (100%), the highest number of roots (13.2 root/explant), and the longest roots (8.44 cm), respectively, on half strength MS medium. Plantlets obtained were transferred to pots and acclimatized with 90% success.

Survival of bristly locust (Robinia hispida L.) in an emulated organic silvopasture

Bristly locust ( Robinia hispida L. [Fabaceae]) is a native tree legume that has received relatively little scientific attention from an agronomic perspective. The objective of this research was to assess transplant survival of bristly locust in an emulated organic goat ( Capra hircus L.) silvopasture. Clumps of trees grew well when mechanically transplanted into a warm-season grass-legume sward. Although the number of original live trees decreased 5 mo after transplanting by about 50%, the number of new shoots arising from rhizomes 2 y after transplanting was 5.3 shoots per plot (range 0 to 26 shoots), at an average distance of 1.4 m from the original clump (range 0.5 to 2.4 m). Our survival and growth data suggest that bristly locust may be well suited for organic livestock browse because of good performance in competition with existing herbaceous vegetation, but further research is needed on its nutritive value, presence or absence of antinutritional factors, and grazing management.

Qualidade de luz e fitorreguladores na multiplicação e enraizamento in vitro da amoreira-preta 'Xavante'

A técnica de micropropagação apresenta diversas vantagens em relação aos métodos tradicionalmente utilizados na propagação da amoreira-preta, especialmente quanto à maior sanidade das mudas e maior rapidez na obtenção de novas plantas. O objetivo deste trabalho foi verificar a influência dos fitorreguladores 6-benzilaminopurina (BAP) e ácido indolbutírico (AIB), aliados à qualidade de luz, na multiplicação e enraizamento in vitro, respectivamente, da amoreira-preta cultivar 'Xavante'. O delineamento experimental utilizado foi inteiramente casualizado. Os tratamentos constituíram-se de diferentes níveis de qualidade de luz (azul, vermelha, branca e ausência de luz) combinadas com ausência ou presença dos fitorreguladores AIB (0,5mg L-1) e BAP (0,8mg L-1) no meio de cultivo. A utilização de BAP aumenta o número de brotações, gemas e folhas da amoreira-preta 'Xavante' e, dessa forma, é indicada para sua multiplicação in vitro. A utilização de AIB não é necessária no enraizamento in vitro da amoreira-preta 'Xavante', indicando que essa cultivar apresenta bom enraizamento natural.

THE EFFECT OF EXPLANT TYPE AND NUTRIENT MEDIUM ON THE IN VITRO PROLIFERATION OF OLIVE (OLEA EUROPAEA L. 'CHONDROLIA CHALKIDIKIS')

The effect of explant type and nutrient medium on in vitro proliferation of olive (Olea europaea L. ‘Chondrolia Chalkidikis’) was studied. The explants, taken from shoots of olive plants grown in a greenhouse, were divided into three groups: young shoot tips, uni- and bi-nodal explants. Furthermore, half of the explants maintained part of their leaves while the rest were defoliated. The explants were established in the OM nutrient medium containing BA (1.0 mg L-1) and IBA (0.5 mg L-1). After a 4-week period, it was observed that the type of explant affected significantly the in vitro proliferation of olive. Specifically, the bi-nodal explants without leaves had the highest proliferation rate and developed the greatest number and the longest new shoots. The young olive shoot tips died as a result of the disinfection process conducted before the establishment of the in vitro culture. Afterwards, three types of nutrient media were used for the in vitro multiplication of olive: the Olive Medium (OM), the Murashige and Skoog (MS) and the Woody Plant Medium (WPM). The concentration of the macronutrients of the above media was the normal or reduced to half or doubled (OM, ½OM, 2OM, MS, ½MS, 2MS, WPM, ½WPM, 2WPM). In all treatments BA (1.0 mg L-1) and IBA (0.5 mg L-1) were included. The experiment lasted 4 weeks. Not only the nutrient medium but also the macronutrients’ concentration affected the in vitro proliferation of olive. The highest proliferation rate was observed when the full strength OM nutrient medium was used, while the MS medium presented the smallest rate, independently of the salt concentration. The greatest number of new shoots was developed in the 2WPM medium, while the longest ones in the full strength OM medium. Finally, hyperhydricity was observed in all the treatments but it was more severe in the cases of the explants cultured in the MS culture medium.

Growth and Nutrient Uptake Responses of Kinnow to Vesicular Arbuscular Mycorrhizae

In a field experiment, three-year-old Kinnow trees budded on Jatti Katti (C. jambhiri) rootstock were inoculated by three different arbuscular mycorrhiza (AM), Glomus manihotis (T1), Glomus mosseae (T2), and Gigaspora gigantia (T3), separately or in combination (T4). Microscopic assessment of AM colonization on Kinnow roots showed a relatively lower level of infection by different species when inoculated separately than when inoculaed together. Application of AM improved growth parameters like plant height, canopy volume, mean leaf area, and number of new shoots per plant but had no effect on trunk diameter, number of leaf per new shoot and new shoot diameter. Flowering phenology was also altered by AM infection. The infected plants produced more flowers which despite abscission caused an increase in the initial number of fruits. AM inoculation increased plant phosphorous in T3, potassium in T1, T2, T3, calcium in T2, T3, T4, and the AM-nutrient relationship did not reveal any generalized pattern. Inoculated plants, however, had higher concentration of different elements by the second year of the experiment indicating towards the continuous and cumulative effect of AM infection on plant nutrient accumulation. Further, the beneficial effects of AM on Kinnow were not related to the difference in the species of mycorrhiza.

Growth and yield potential of Echinochloa pyramidalis (Lam.) Hitchc Chase: A forage plant used in vertical-flow constructed wetlands in Cameroon

This work aims at assessing growth and productivity of Echinochloa pyramidalis in the saline and saline-flooded processes of wetland treatment. Growth characteristics such as density, number of dead plants, height and number of new shoots and biomass production of the plant were studied using 24 laboratory-scale units of vertical-flow constructed wetlands fed with faecal sludge supernatant. Plants collected from the surrounding wetlands were subjected to four salinity levels with electrical conductivity of 2, 3, 6 and 9 dS.m-1 under both drained and flooded conditions for a 100 day period. The results revealed that salinity and flooding combined with salinity stresses had similar effect on plant survival, height and density, leading to growth and biomass reduction at the higher salinity level than under natural growth conditions. Despite these stress effects, E. pyramidalis remained healthy with no signs of salt or saline-flooding stress injury but higher biomass production. As E. pyramidalis is a forage plant its high biomass production in the wetland treatment systems shows the potential of wetland systems to create a local economy based on forage production and thus the opportunity to link sanitation stewardship to food production. This may contribute to sustain sanitation infrastructures at the same time as increasing food security, especially in developing countries. Key words: Constructed wetlands, Echinochloa pyramidalis, faecal sludge, flooding, growth, salinity, yield potential

Can time-weighted average concentrations be used to assess the risks of metsulfuron-methyl to Myriophyllum spicatum under different time–variable exposure regimes?

We tested the effects of the herbicide metsulfuron-methyl on growth of the submerged macrophyte Myriophyllum spicatum under laboratory conditions using different exposure scenarios. The exposures of each scenario were comparable in the concentration × time factor, viz., the same 21-d time-weighted average (TWA) concentrations but variable in peak exposure concentrations (ranging from 0.1 to 21 000 ng ai L −1) and exposure periods (1, 3, 7, 14 or 21 d). To study recovery potential of the exposed M. spicatum plants we continued the observation on shoot and root growth for another 21 d in herbicide-free medium so that the total observation period was 42 d. Non-destructive endpoints, length and number of new shoots and roots, were determined weekly from day 14 onwards. Destructive endpoints, dry-weight (DW) of main shoots, new shoots and new roots, were measured at the end of the experiment ( t = 42 d). Metsulfuron-methyl exposure in particular inhibited new tissue formation but was not lethal to main shoots. On days 21 and 42 after start exposure, EC 10/EC 50 values for new tissues expressed in terms of peak concentration (=measured concentration during exposure periods of different length) showed large differences between exposure scenarios in contrast to EC 10/EC 50 values for days 21 and 42 expressed in terms of 21-d and 42-d TWA concentrations, respectively. At the end of the experiment (day 42), 42-d TWA EC x values were remarkably similar between exposure scenarios, while a similar trend could already be observed on day 21 for 21-d TWA EC x values. For the macrophyte M. spicatum and exposure to the herbicide metsulfuron-methyl the TWA approach seems to be appropriate to use in the risk assessment. However, the data from the toxicity experiment suggest that on day 21 also the absolute height of the pulse exposure played a (minor) role in the exposure – response relationships observed.

Canopy Management in Mango (Mangifera indica L.) cv. Alphonso with reference to Growth and Physiological Characters under Ultra High Density Planting

A field experiment was conducted to find out the effect of different pruning levels on growth and physiological characters in mango (Mangifera indica L.) cv. Alphonso under ultra high density planting during 2010-2011 at Jain Irrigation Systems Limited (JISL) Farms, in Tamil Nadu. The treatments viz., control, light pruning, moderate pruning, heavy pruning, 50 per cent removal of past season growth and total removal of past season growth were imposed on five-year-old uniform sized Alphonso trees grown under spacing of 3 x 2 m. The highest fresh weight of pruned branches and maximum number of new flushes after pruning were registered in T 6 (total removal of past season’s growth). The same treatment recorded the maximum C: N ratio in leaves and shoots during harvesting stage. The highest tree height and canopy diameter (EW and NS) were recorded in T 1 (control). The treatment T 4 (heavy pruning) registered the maximum number of new shoots (8.20) emerged from pruned branch after pruning. The highest number of new shoots per plant was registered in control (T 1 ). The pruning treatments also influenced total chlorophyll contents. Control trees recorded the highest leaf area index in all months of observation compared to other treatments. The treatment T 5 (50 per cent removal of past season’s growth and tipping) recorded the highest light transmission ratio among the treatments.

BENZYLADENINE INCREASES BRANCHING OF HERBACEOUS PERENNIALS

Many of the herbaceous perennials, especially the newer cultivars of Echinacea, are poorly branching, slow to fill out the pot, and produce few propagules. Configure (6-BA, Fine Americas, Inc.), a new product recently labeled for branching of floricultural crops, was evaluated on a variety of perennials over two seasons. Configure was applied once as a foliar spray at rates of 0, 300, 600, 900 or 1200 mg/L to established plants grown in 1.1-L pots filled with a peat/pine bark medium. Plant height and number of branches were determined at 2-week intervals after treatment (WAT). In spring trials, Configure improved the basal branching of Echinacea purpurea ‘Double Decker’ with a three-fold increase in the number of new shoots per plant with a single foliar application of 300 mg/L (control 1.0 vs. 300 mg/L 3.8 shoots at 2 WAT). Higher rates further increased the number of basal shoots. Echinacea purpurea ‘White Swan’ had a better branching habit and was more responsive to Configure with increased branching at 4 WAT with treatment of 300 mg/L; again higher rates increased the number of new branches. Vinca minor ‘Sterling Silver’ showed a significant quadratic increase in the number of branches at 4 WAT with Configure which did not persist but suggests that there may be value in multiple applications. Coreopsis verticillata ‘Zagreb’ plants treated with Configure had increased branches at 2 WAT that also did not persist. In Fall trials, branching of Echinacea ‘Ruby Star’ increased nearly 2-fold (control 2.6 vs. 300 mg/L 5.0 shoots) at 2 WAT. Similar results were observed with Echinacea ‘Magnus’. Clematis jackmanii, Phlox paniculata ‘Bright Eyes’, Buddleia × weyeriana ‘Honeycomb’ and Coreopsis rosea ‘Sweet Dreams’, were not responsive to Configure. In all tests, positive results persisted throughout the six to ten week studies. Configure offers a new tool for improving the finished quality and propagation potential of Echinacea cultivars and the potential for improving branching of other herbaceous perennials.

Clonal propagation and cryogenic storage of virus-free grapevine (Vitis vinifera L.) via meristem culture

A protocol for production of virus-free Vitis vinifera using meristem culture was developed. Meristems (0.1-0.2 mm) of V. vinifera infected with grapevine fanleaf virus and grape leafroll associated viruses were excised from 1-year-old growing vines. Shoot tips were cultured on half-strength Murashige and Skoog (MS) medium, supplemented with 0.02 mg L^{-1} of benzylaminopurine (BAP) and 0.01 mg L^{-1} of naphthalene acetic acid (NAA). BAP and kinetin resulted in differences in the number of new shoots per explant, shoot height, and number of new leaves per explant. BAP at 0.8 mg L^{-1} gave the highest in vitro multiplication rate, with 5.25 shoots per explant, whereas elongation was greatest in the presence of 0.2 mg L^{-1} of kinetin. Root initiation was tested on an MS medium supplemented with 0.0, 0.2, 0.4, 0.6, 0.8, or 1.0 mg L^{-1} of IBA (indole-3-butyric-acid), IAA (indole-3-acetic-acid), or NAA. Maximum root number was achieved using 0.6 mg L^{-1} of IBA. A survival rate of 95% was achieved when rooted explants were acclimatized ex vitro in a mixture of 1 soil: 1 perlite: 1 peat. Acclimatized plants grew in the greenhouse and were maintained as virus-free plants. Visual inspections as well as results of RT-PCR, using virus-specific oligonucleotide primers, showed that plants developed in vitro were free from grapevine fanleaf virus, grape leafroll associated virus-1, and grape leafroll associated virus-3 infections. Shoot tips from plantlets grown in vitro were cryopreserved by vitrification. Shoot tips were treated in a 2 mL cryotube filled with a solution of 5% (w/v) DMSO, 5% (w/v) glycerol, and 5% (w/v) sucrose at 25 °C for 20 min, then dehydrated with 1 mL of modified vitrification solution 2 (MPVS2) at 0 °C for 40 min. Maximum regrowth (55%) was obtained after cryogenic storage with cultures exposed to MPVS2 for 40 min at 0 °C. Cryopreserved shoot tips, after being warmed, resumed growth within 7 days and developed shoots directly without intermediate callus formation.

EFFECTS OF CHITOSAN CONCENTRATION ON IN VITRO GROWTH OF DENDROBIUM HYBRID SEEDLINGS

Chitosan is a reported plant stimulant. The objective of this work was to study the effect of chitosan on in vitro growth of Dendrobium hybrid seedlings. Two-month-old seedlings of Dendrobium 'White Pancy Lip' plants were sorted at the same size (approximately 1.2 to 1.5 cm in height) and were cultured on modified Vacin and Went (VW) medium supplemented with chitosan at the concentration of 10, 20, 40, 60 mg/L or without chitosan (control). Leaf numbers, the number of roots and the number of new shoots were recorded weekly. After 3 months, chitosan at 20 mg/L increased root number (1.68 roots per plant). Seedlings grown on VW supplemented with chitosan at 10 and 20 mg/L at week 11 had a higher leaf number compared with other treatments. The highest number of new shoots was found in VW media supplemented with chitosan at 20 mg/L. The effect of chitosan on the morphological characteristics of the adaxial leaf side showed that all chitosan treatments had a lower stomata number, but a larger stomata size compared to the control. On the abaxial leaf side, the concentration of chitosan did not affect stomata number and size, but chitosan at the concentration of 10 mg/L had the highest number of chloroplasts (31.1 chloroplasts) compared to other treatments.

Effect of Flooding Depth on Growth, Biomass, Photosynthesis, and Chlorophyll Fluorescence of Typha domingensis

We examined the growth, biomass, photosynthesis, and chlorophyll fluorescence of Typha domingensis (southern cattail) in response to a six-week period of three flooding depths: 40, 91, and 137 cm above the soil surface and a subsequent four-week period of recovery at a 40-cm flooding depth. The 91- and 137-cm flooding significantly decreased the following: number of new shoots, number of live leaves, leaf, belowground and total biomass, and belowground biomass/leaf ratio. Plants flooded to a 91- or 137-cm depth had significantly lower chlorophyll concentration, photosynthesis, and fluorescence (Fv/Fm) as well as higher dark respiration and light compensation points than those exposed to the 40-cm flooding. Following the recovery period, most adverse impacts caused by the 91-cm flooding depth were reversed in terms of biomass, photosynthesis, and chlorophyll fluorescence, while the effect of the 137-cm flooding stresses exhibited by T. domingensis were not reversed. Flooding to a 137-cm depth is detrimental to T. domingensis and needs to be avoided. Our results indicate that depth-duration thresholds for management of T. domingensis dominated marshes are necessary to minimize deepwater impacts to vegetation communities.

The Interaction Effect Among the Existing Eyes Numbers of the Cuttings Grape and Treatment by IBA Powder in the Improvement of the Root Growth

This research was conducted in the plastic houses at Horticulture Dep. College of Agriculture and Forestry Mosul University, Iraq, to study the effect of three concentrations of auxin IBA 0, 1000 and 2000 mg/L and number of eyes on cuttings with two or three eyes on rooting and growth parameters of hardwood Grape cuttings. After Twelve weeks from culture date cuttings examined for rooting and vegetative growth. Cuttings with three eyes significantly show increase in all parameters as compared with cuttings with two eyes(rooting percentage, root number and length, fresh and dry root weight, new shoots, new leaves, number and length of new shoots, fresh and dry vegetative weight parameters, at the same time the two concentrations of auxin IBA 1000 and 2000 mg/L increased significantly all rooting and vegetative parameters, except the percentage of rooting and number of new shoots. However the interaction treatment (cutting with three eyes + 1000 mg/L IBA) gave a 100% of rooting percentage, but the highest average of ( root number and length , new leaves, number and length of new shoots) resulted from cutting with three eyes treated with 2000 mg/L IBA value which reached 20.10, 8.06cm, 15.77 , 2.27 and 11.72cm respectively .

GROWTH AND BIOCHEMICAL CONSTITUENTS OF OLIVES AS INFLUENCED BY IRRIGATION WITH TREATED INDUSTRIAL WASTEWATER

The suitability of treated industrial wastewater for irrigation of ‘Improved Nabali’, ‘Nabali’, and ‘Manzanillo’ olives was investigated. Irrigation with six electrical conductivity (EC = 0.78, 1.0, 2.0, 3.0, 4.0 and 5.0 dS m-1, respectively T0, T1, T2, T3, T4, T5) were compared in the greenhouse experiment. The olive trees in the field experiment were trickle-irrigated with potable water and treated wastewater. Regardless of the cultivar, length and number of new shoots, diameter of the main trunk, leaf area and dry weight of the plants were significantly enhanced under the influence of different treatments. ‘Improved Nabali’ was the most positively affected cultivar. The leaf biochemical contents from proline and total chlorophyll contents showed no variations among the treatments and cultivars. Proline content was enhanced by irrigation with wastewater only under the field condition. Olive oil acidity and peroxide value were not affected by treatments. These results indicate that this kind of wastewater is suitable for application to olive orchards under irrigation with continuous monitoring of mineral levels.

Effect of Light Intensity on Arundinaria gigantea Growth and Physiology

The once dominant Arundinaria gigantea canebrake ecosystems have been reduced to fragmented populations less than 2% of their former extent resulting in a critically endangered ecosystem. Restoration of canebrakes is thus necessary for maintaining and enhancing biodiversity in the southeastern United States. Contemporary fragments of canebrakes are trapped between anthropogenic development and closed canopy forests. The goal of this study was to assess the impact of light intensity on rivercane growth and physiology in both laboratory and field studies and thereby enhance restoration success. A laboratory experiment was conducted to test light (partial shading and no shading) and nitrogen (0, 0.5, 5.0, 25, and 100 g/L) effects on seedling growth. Potential interaction occurred between light and nitrogen. Levels of nitrogen up to ten times the commercially recommended amount (0.5 g/L) significantly increased seedling growth when plants were grown under non-shaded conditions. A thinning site was established in an existing rivercane population and forest canopy was reduced 60% by girdling overstory trees. Number of new shoots and new shoot diameter were both increased by thinning. In addition, light response curves demonstrated that rivercane had a typical C3 light response pattern and field readings showed that rivercane maintained net photosynthetic activity throughout the dormant season. Results indicate that rivercane growth is enhanced with increased light levels. Reduction of overstory canopy is a potential management tool for enhancing survival and growth of existing populations.

Ethylene influences development and flowering of Ptilotus spp. in vitro and ex vitro

The genus Ptilotus has immense potential for ornamental horticulture but its commercial development has been hindered by propagation limitations. Poor seed quality and germination are reported. Cutting propagation is limited by cutting supply as the juvenile phase of Ptilotus is short. Micropropagation has been used in an attempt to overcome these difficulties but explants become floral in vitro and this causes plantlets to elongate. Ethephon has been used to control flowering of stock plants of many ornamental species. This study investigated the effect of ethephon applied to young (3-week-old, deflasked from tissue culture) and mature (1-year-old) Ptilotus plants in a greenhouse. A system of applying gaseous ethylene at 0, 100, 200 and 300 mg l −1 to the headspace of in vitro plantlets in glass jars was developed and the response of in vitro plantlets to ethylene studied. One-year-old Ptilotus plants were treated with 500 mg l −1 ethephon 2 days before pruning or 1 or 2 weeks after pruning. Ethephon application 2 days before pruning decreased the number of inflorescences and increased the number of shoots (compared to the control) but was phytotoxic. Ethephon applications of 150 or 300 mg l −1 applied weekly or fortnightly to 3-week-old plants deflasked from tissue culture reduced plant height and number of inflorescences and at low concentrations increased the number of new shoots. A fortnightly application at 150 mg l −1 is recommended. Previous reports on the effects of ethylene on inflorescence production on plantlets in vitro are limited. Our study showed that exposure of in vitro plantlets of P. nobilis to ethylene gas at 100 mg l −1 for 1 h significantly increased the number of shoots and plant height but this did not occur for plantlets of P. spicatus. Plantlets of P. spicatus exposed to transient ethylene at 200 and 300 mg l −1 showed significantly greater rooting (52.4%) than the control (13.6%).

Methods of limiting willow shrub re-growth after initial removal on fen meadows

Shrub removal is commonly used for management and restoration of species-rich fen meadows. A common problem after initial shrub cutting of willow is a vigorous re-sprouting and quick re-growth. In this paper we test experimentally what is an effective management option, limiting the re-growth of willow after cutting, on peat soils. In this experiment (split-plot set-up) we tested mowing of different intensity, removal of young shoots by hand and herbicide application, to find out which of them effectively limits willow re-growth. All applied treatments limited re-sprouting, but to different extents. We found that mowing had a strong, negative effect on increase in height of the shoots and on increase of the number of leaves, while an application of Roundup strongly limited the number of new shoots, in comparison with control. When all measured characteristics were accounted for, the combination of Roundup use and annual mowing was most effective. If the use of herbicide is to be avoided, intensive mowing in the first years (×2 or ×3) should be applied, followed by annual mowing. We concluded that removal of young shoots by hand did not have a stronger effect in weakening the willow re-growth than mowing. The treatment with herbicide application alone was not effective.

Phenotypic variation among five provenances of Pterocarpus angolensis in Zimbabwe and Zambia

The feasibility of utilising morphological markers for determining existing provenance variation in the African savanna tree Pterocarpus angolensis was assessed. Five provenances were used: Mtao, Gokwe, Nyazura, Chesa (Zimbabwe) and Kapirimposhi (Zambia). Two weeks after germination, seedlings were inoculated with mycorrhizal inoculum and raised in a glasshouse. Height and collar diameter were measured at one, three and five months of age (before stem dieback), and at 14 months (after stem dieback). At the time of dieback, percentage of seedlings losing leaves, stem dieback and mortality were recorded; numbers of new shoots produced in the recovery period were also determined. To further assess growth, leaf, stem and root dry biomass were measured after stem dieback at 14 months. At one month, Chesa seedlings were the tallest and Kapirimposhi seedlings were significantly shorter (p < 0.05) than the rest of the provenances. However, at three and five months of height growth no significant differences were observed. At one month, diameter growth was significantly different with the Kapirimposhi provenance having the smallest diameter (p < 0.05). At three and five months of seedling growth only the Gokwe provenance was significantly different from the rest of the provenances. By seven months of age, stem dieback was observed and foliage loss was over 60% in each of the five provenances. At 14 months of seedling growth after stem dieback the Nyazura and Kapirimposhi provenances were significantly shorter, whereas there were no significant differences in diameter growth and dry biomass from root, stem, leaf or root:shoot dry biomass ratio. Fourteen months after germination new shoots emerged from various axillary bud positions depending on the extent of dieback.