Chilling requirements of Paeonia cultivars

Dormant second year potted plants of Paeonia ‘Coral Sunset’, ‘Monsieur Jules Elie’, and ‘Sarah Bernhardt’ were placed into three chilling regimes (constant 1, 4, or 7°C) for different durations (3, 6, 9, or 12 weeks) to ascertain their chilling requirements for shoot and flower production. Chilling was followed by forcing for up to 5 weeks at 18°C, then plants were maintained in a controlled greenhouse until flowering had finished. Mean number of shoots and flowers per plant were recorded and the time taken for shoots to sprout was calculated.Control plants (forced immediately without chilling) produced no shoots or flowers. For all cultivars, the proportion of plants that sprouted, and the mean number of shoots and flowers increased as plants were subjected to colder chilling temperatures, or longer chilling durations. However, there were no significant within-cultivar differences between different treatments of 9 weeks or more. The time taken for sprouting to occur after the completion of each chilling treatment consistently decreased as the duration of the chilling treatment increased. In most cases, lower chilling temperatures lead to more rapid sprouting once plants were placed in the 18°C forcing conditions.When a simple model was fitted where the chilling temperature and duration of each treatment was described by a cumulative normal curve rising from zero to some maximum value (or potential) once adequate chilling had been received, we found that temperatures of 4 and 7°C provided only 83 and 59%, respectively, of the chilling accumulated per unit time at 1°C. ‘Coral Sunset’, an interspecific hybrid early flowering type, required the greatest amount of chilling to sprout consistently, while ‘Sarah Bernhardt’, a very late flowering type, required the least. Of the three cultivars, ‘Sarah Bernhardt’ also required the least amount of chilling to achieve its potential shoot and flower numbers, while ‘Monsieur Jules Elie’, a mid-season flowering type, required the most chilling to achieve the same end for these two variables. This suggests that the response to spring temperatures as well as chilling influences the time of flowering.     

Stockplant factors affecting root initiation in cuttings of Triplochiton scleroxylon K. Schum., an indigenous hardwood of west africa

The ability of auxin-treated T. scleroxylon cuttings to root was affected by the prior management of potted stockplants. In undecapitated single-stem stockplants more cuttings from upper rather than lower mainstem nodes rooted; a difference paralleled by leaf water potential immediately after severance, although there was also a positive relationship with internode length. The rooting percentage of mainstem cuttings from unpruned stockplants ranged from 15% to 43% whereas that of cuttings from the lateral shoots of pruned stockplants ranged from 40% to 83%. Considerably more cuttings rooted from stockplants which were severely pruned than from those where decapitation removed only the top node; there seemed to be an inverse relationship with the number of shoots per plant and the carbohydrate: nitrogen ratio. However, in tall pruned stock- plants, more cuttings from lower lateral (basal) than from upper (apical) shoots rooted, although the differences between cuttings from basal and apical lateral shoots were less when the stockplants’ mainstems were orientated at 45° or kept horizontal, instead of vertically. Adding NPK 16 weeks before harvesting cuttings from 10-node vertical stockplants increased the rooting ability of cuttings from basal shoots without affecting the rooting of those from apical shoots. More lateral shoot cuttings rooted when two, instead of one or four lateral shoots were allowed to develop per stockplant, this being associated with less cutting mortality than occurred in pruned stockplants. In stock- plants with two shoots, cuttings from basal lateral shoots rooted better than those from apical shoots, although without competition from basal shoots. The rooting of apical shoots was enhanced by application of a complete fertilizer. The presence of basal shoots reduced the rooting ability of apical shoots even with the fertilizer application. Many of the effects of lateral branch position on rooting may be related to light intensity, for greater rooting percentages occurred among cuttings from lower, more shaded, than from upper less shaded branches. This positional effect was eliminated when branches were uniformly illuminated.     

Production of high quality Ardisia plants by stem tip cuttings

To produce commercially acceptable Ardisia plants, stem tip cuttings from mature plants were rooted and forced in greenhouses. Ten centimeter long cuttings were either treated with 200 ppm 1-naphthalene acetic acid (NAA) for 2 h, 2000 ppm indole-3-yl-butyric acid (IBA) for 10 s, or 0.5 and 1.0% IBA powder prior to sticking them in the rooting medium. Rooting percentage at 45 days exceeded 76% with 2000 ppm IBA treatment which was a significant increase over non-treated control. Rooted cuttings developed into three types of plants: those forming only vegetative shoots without flowers, those forming reproductive shoots with flowers, and those forming both vegetative and reproductive shoots. The ideal plant produced only vegetative shoots when rooted cuttings were transplanted into pots. About 50% rooted cuttings were forced to finish, producing 31 or 40% of high quality plants when rooted cuttings with vegetative shoots were grown in a greenhouse (GH) at temperatures higher than 21/19 °C (day/night) in 1995 or 21/18 °C GH in 1997, respectively. This method shortened the total production time to less than 2 years as compared to 4 years when starting from seeds.     

Asexual Propagation of Grapevine Transmits Pierce’s Disease Pathogen (Xylella fastidiosa) to Rooted Cuttings

An objective of this study was to investigate rooting success of grape cuttings propagated from vines symptomatic of Pierce’s disease. Additional objectives were to assess if rooted cuttings could survive and produce viable plants, and determine if Xylella fastidiosa (causal agent of Pierce’s disease) could be found in rooted cuttings. In Jan. 2008, cuttings were taken from symptomatic and asymptomatic ‘Merlot’ and ‘Cabernet Sauvignon’ grapevines growing in the Hill Country and Gulf Coast regions of Texas. Six weeks after cuttings were propagated, each cutting was uprooted and evaluated for rooting and infection parameters. Cuttings were then planted in containers and held in the greenhouse to evaluate survivability. To confirm the presence of X. fastidiosa, propagated cuttings were tested by real-time polymerase chain reaction. Data indicate several rooted cuttings tested positive for X. fastidiosa and appeared viable and healthy. Therefore, vines infected with X. fastidiosa have the ability to produce asexually propagated cuttings, and potentially contaminate non-infected vineyards.     

Standardization of Rootstocks of Mango (Mangifera Indica L.)

Mango cuttings could be induced to form roots provided IBA at 5,000 p.p.m. in lanolin was applied at the base of shoots after removing a ring of bark while they were still attached to the mother tree.

Cuttings taken from one-month-old seedlings gave the highest percentage of rooting and establishment, but with increasing age of the mother plants the rooting was considerably reduced. The rooting of cuttings of different age groups could be improved by using shoots forced into vigorous growth by hard pruning. Younger plants responded better to such treatment than older ones.

Cuttings from etiolated shoots rooted better than those from non-etiolated, but etiolation was less effective in promoting rooting than invigoration by hard pruning. Etiolation and invigoration combined gave the highest percentage of rooting and establishment in all age groups.     

Effects of cold storage on postharvest leaf and flower quality of potted Oriental-, Asiatic- and LA-hybrid lily cultivars

The effects of cold storage of mature potted plants on postharvest leaf and flower quality were investigated in several cultivars of three major groups (Oriental, Asiatic and LA) of hybrid lilies (Lilium spp.). Mature plants were stored in darkness at 3 °C for 2 weeks before placing them in a postharvest evaluation room (22 °C) and were compared with plants moved directly to the evaluation room. The efficacy of GA₄₊₇ plus benzyladenine (BA) treatments (applied just before cold storage) for preventing cold-induced postharvest disorders in each cultivar was also evaluated. In all cultivars, cold storage caused several adverse effects on postharvest quality, including accelerated leaf yellowing or browning, bud abortion and reduced flower or inflorescence longevity. Leaf abscission was observed only in Oriental-hybrids. Treatment with GA₄₊₇ plus BA significantly reduced these disorders and improved the overall postharvest quality after cold storage. While different cultivars differed greatly in their sensitivity to cold storage, all the cultivars benefited from GA₄₊₇ plus BA treatment. Experiments indicated that GA₄₊₇ plus BA treatments could be applied as early as 2 weeks before the mature bud stage without compromising the positive effects.     

Partitioning sources of rooting potential in plum hardwood cuttings

SUMMARY

Rooting of leafless winter hardwood cuttings of the plum rootstock Prunus insititia ‘Pixy’ increased as the location from which the shoots were taken from within specially grown stockplants decreased in height above ground, associated with a parallel reduction in shoot thickness. However, the actual height of the least-ready-rooting crown cuttings had no effect on rooting, suggesting that relative rather than absolute position is important. Rooting was unaffected by bark-ringing and trunk incision distal to the shoot position, suggesting that such treatments did not interfere with a basipetally translocated root promotor which might have accounted for improved rooting of cuttings in the lower parts of the hedge. The rooting of crown cuttings above a bark ring was reduced considerably compared with that of cuttings from normal bushes, and this was associated with increased thickness of shoots distal to the ring. Delaying pruning in spring until after growth had started resulted in thinner crown shoots compared with those from plants pruned normally while dormant, and the rooting of these thinner crown shoots was much higher than that of the normal crown cuttings. It was shown by covariance analysis that shoot thickness accounted for part of the rooting response but could not account for the total effect due to shoot position within the bush, ringing, or time of pruning. Competence to root appears to develop independently in individual shoots, modified by a shoot thickness factor which favours the subordinate shoots induced in the shoot hierarchy of severely pruned hedges.     

Manipulation of bolting and flowering in celery (Apium graveolens L. var. dulce). III. Effects of photoperiod and irradiance

SUMMARY

Photoperiods of 8 and 16 h during chilling at 5°C had no effect on bolting and macroscopic flower appearance in celery cv. New Dwarf White. Eight hour photoperiods during chilling however markedly increased the number of plants forming sessile flowers. Short photoperiods (8 h) after chilling decreased the proportion of young, but competent plants that bolted and flowered. Total darkness during chilling completely prevented any subsequent vernalization response either as bolting or as flowering. Reducing irradiance receipt by the plants during chilling from 85 to W m"2 (PAR) had no effect on their vernalization response. After chilling, a reduction in mean daily total irradiance in the glasshouse from 4.05 to 1.57 MJ m"2 d-1 had no effect on bolting and flowering. Confinement of competent plants to darkness for 4-8 d at 20°C just prior to chilling resulted in a highly significant delay (F>0.001) to bolting and reduced the number of plants flowering. Two days of darkness had no significant effect. The inhibitory effects of dark treatments prior to chilling was greater in plants chilled subsequently for six weeks than for nine weeks.     

Interaction of source-plant age and shoot ringing on rooting of cashew (Anacardium occidentale L.) cuttings

Summary

IBA-treated cuttings rooted only when prepared fom bark-ringed shoots. The response to ringing declined with increasing age of the tree. However, on marcotting, the ringed shoots of four year old trees showed more and earlier rooting.     

Rooting of chrysanthemum cuttings. Influence of irradiance during stock plant growth and of decapitation and disbudding of cuttings

Stock plants of Chrysanthemum morifolium Ramat. cultivar ‘Improved Mefo’ were grown in a controlled-environment room at different levels of irradiance (9, 23, 53 or 90 W m^?2). After 3 weeks, cuttings were excised and rooted for 3 weeks at an irradiance of 16 W m^?2. Cuttings from stock plants grown at the highest irradiance had the highest number of roots, while cuttings from the lowest irradiance had the lowest number of roots.The importance of the presence of shoot meristems for root formation was investigated through disbudding and decapitation at different times after the excision of the cuttings. Removing the buds on the day of excision had no effect on the number of roots formed, while the removal of the buds on day 2 to day 5 after excision had a promotive effect. Removal later than 7 days after excision had no effect at all.The results are discussed from the point of view that an interaction between nutritional and hormonal factors regulates the process of root formation.     

Interaction of stock plant irradiance and auxin in the propagation of apple rootstocks by cuttings

The purpose of the investigation was to examine the effects of different irradiances (light intensities: 8, 16, 38, 54 W/m²) to stock plants on the subsequent rooting of cuttings taken from these stock plants.If the cuttings were rooted without treatment with auxin (indole butyric acid), there was no difference in rooting attributable to the irradiance pretreatments. Auxin treatment of the cuttings was most effective in increasing root numbers and rooting-percentage in cuttings taken from stock plants grown under 8 W/m².     

Changes in endogenous abscisic acid and soluble sugars levels during dormancy-release in bulbs of Lilium rubellum

Changes in endogenous abscisic acid and soluble sugars levels during dormancy-release of lily bulbs of Lilium rubellum were investigated. Shoot emergence and flowering of the bulbs stored for 14 weeks at 4 °C occurred more synchronously, and the time span from first to last flower in the plants was shorter than those of bulbs stored for 10 weeks at 4 °C. Longer duration of bulb storage showed accelerating effects of increasing leaf number and stem length but negatively affected flower size. Flower number per plant was not much influenced by bulb storage duration. Concentration of endogenous abscisic acid (ABA) level in the bulbs during bulb storage decreased as storage duration increased, and it remained at a constant level after being stored for 10 weeks. This result suggests that the decrease in the endogenous ABA level during bulb storage is correlated with dormancy-release. Concentrations of soluble sugars also changed during bulb cold storage. Sucrose concentration increased as the chilling term increased to 10 weeks but decreased afterward. Glucose and fructose increased from the beginning of chilling to the end of a 14-week cold storage.     

Differentiation of the dynamic variables affecting rooting ability in juvenile and mature cuttings of cherry (Prunus avium)

Summary

The rooting potential of four types or origins of Prunus avium cuttings from the same mature trees (over 20 years-old) was compared using a mist propagation bed during early Summer (June). The cuttings originated from juvenile sucker shoots of the current and previous year, and mature crown shoots (current year’s lateral ‘long-shoots’ and multi-year terminal ‘short shoots’). The morphological differences in inter-node length, stem diameter and leaf area between the four cutting types were highly significant (P = 0.05), leading to large differences in cutting volume and, so it is argued, to assimilate reserves. Juvenile cuttings rooted well (65% and 77% rooting for hardwood and softwood shoots, respectively), while mature cuttings rooted poorly (4% and 7% for mature hardwood and softwood cuttings, respectively). Leaf abscission was significantly more frequent in mature hardwood cuttings (16 – 78%) than in the other cutting types (1.6 – 9%) at the end of the propagation period. Leaf loss resulted from two processes: abscission and leaf rotting. Physiologically (i.e., in carbon assimilation, leaf transpiration and stomatal conductance), the four cutting types were not significantly different early in the post-severance period (day-4); but, by day-22, stomatal conductance was lowest in mature hardwood cuttings that still had leaves. At this time, the most physiologically-active unrooted cuttings were from juvenile hardwood and mature softwood shoots. The extent of physiological and morphological variability between cutting types and their probable impact on processes affecting rooting ability is complex and highly interactive. Consequently, it is not possible to explain the causes of the variation in rooting ability between juvenile and mature cuttings, although this study suggests that the constraints to rooting are likely to reflect physiological differences between the different cutting types. It is concluded that, to resolve the debate about factors that affect the rooting ability of juvenile and mature cuttings (i.e., ontogenetic vs. physiological ageing), there is a need to achieve morphological and physiological comparability in the tissues.     

Effect of storage regimes on pectolytic enzymes,pectic substances,internal conductivity and gel breakdown in cold stored ‘Songold’ plums

Summary

Plums (Prunus salicina cv. Songold) were cold stored according to a single-temperature regime comprising 28 d at ?0.5°C, and a dual-temperature regime comprising 10 d at ?0.5°C followed by 18 d at 7.2°C. After cold storage, the plums were ripened for 8 d at 10°C. Pectolytic enzyme activity, pectic composition, internal conductivity and gel breakdown were determined at seven stages during storage and ripening. Although not exposed to chilling temperatures prior to harvest, approximately 10% of the plums exhibited gel breakdown at harvest, indicating that the disorder cannot be classified solely as a cold-storage chilling disorder. The higher temperatures of the dual-temperature regime resulted in higher polygalacturonase activity than with the single-temperature fruit. Consequently, protopectin degradation and the concomitant production of water- soluble pectins were greater in the dual-temperature fruit. Single-temperature storage resulted in higher pectinmethylesterase activity during the latter stages of storage and during ripening. Increases in temperature after 10 d and 28 d in dual- and single- temperature fruit, respectively, were associated with significant increases in the viscosity of water-soluble pectins, internal conductivity and gel breakdown. The significant positive correlation between internal conductivity and gel breakdown suggested that membrane integrity is closely associated with development of gel breakdown.     

Changes on carbohydrates and nitrogen content in the bark tissues induced by artificial chilling and its relationship with dormancy bud break in Prunus sp.

Stem cuttings of peach, nectarine, plum and apricot, obtained from 1-year-old shoots at leaf drop in autumn, were exposed at a constant 3.0 ± 0.1 °C to simulate different chilling accumulation treatments (0, 500, and 1000 chilling hours). A set of 10 excised shoots was forced to budbreak after chilling accumulation; a second set of 10 excised shoots was used to analyse sugars, starch, and ammonium-, nitric- and proteinaceous-nitrogen content in the bark tissues. Sorbitol, fructose and glucose were the main sugars in the bark tissues, whereas sucrose and rafinose showed the lowest quantities in all Prunus sp. studied. Sorbitol and starch concentration decreased whereas glucose and fructose concentration increased with chilling. Ammonium-nitrogen showed the more dramatic increase with medium chilling treatment, decreasing again at high chilling exposure. No modifications in proteinaceous- and nitric-nitrogen levels were observed due to chilling. Chilling treatments increasing flowering intensity showed high ammonium- and proteinaceous-nitrogen content in the bark tissues of the stem cuttings, whereas those reducing flowering intensity showed high starch and nitric-nitrogen content, in three of the four Prunus sp. studied. Ammonium-nitrogen content gives the highest correlation with flowering intensity.     

Preservation of cuttings of Rhododendron obtusum Planch., R. ponticum L. and R. simsii Planch.

Owing to lack of space or time, cuttings of rhododendrons cannot always be rooted at the moment they are ready for propagation. We investigated how cuttings could be cold stored until the time they are to be rooted. The cuttings can best be preserved at temperatures just above freezing. At higher temperatures the period of successful storage is shortened. The greatest hazard is Botrytis cinerea attack, but this can be prevented by a prophylactic spray with benomyl. More lignified cuttings can be preserved longer than more herbaceous ones. The methods described can be used for storing cuttings of Rhododendron obtusum, ponticum and simsii hybrids.     

Cold Storage of Strawberry Plants

Abstract

Cold storage has not only been a good method to overwinter strawberry plants safely and to compensate for the lack of natural chilling. Initially cold stored plants were used for early spring cropping only. Meanwhile this technique has become a normal commercial practice among growers in central Europe and has given them the opportunity to extend the strawberry production season from July until January. Cold stored waiting bed plants have been used since the early seventies in The Netherlands and Belgium and currently represent an important part of strawberry production. These sixty-day-plants are planted mainly outdoors in the soil for a production from July until September. More recently waiting bed plants have gained popularity in the UK, Germany and northern Italy to extend the season. Alternatively in France and Germany cold stored runner (A+) plants are traditionally being used for a summer production outdoors followed by a spring crop. During the last decade module or tray plants have gained popularity for autumn cropping on substrate culture in plastic tunnels and greenhouses. During the most recent years the programmed “out of season” production of strawberries has become more important in several European countries. Intensive research has been going on concerning the improvement of the growing techniques and quality of plant material and cold Storage conditions.     

Effects of time of collection,growing-conditions of mother plants and growth regulators on rooting of cuttings of Telopea speciosissima (Proteaceae)

Terminal stem cuttings of Telopea speciosissima were collected from two locations at monthly intervals and treated with indolebutyric acid (IBA) in combination with benomyl. Cuttings taken in the first half of spring, at the beginning of vegetative growth, gave the highest percentage of rooted cuttings and the greatest length of adventitious roots per rooted cutting. Cuttings taken from the environment most suited for the growth of the mother plants also produced the highest percentage of rooted cuttings, but their root length did not differ significantly between the two locations. Pre-treatment of cuttings with 4000 p.p.m. IBA (concentrated solution dip method) initially gave the highest percentage of rooted cuttings and longest root length, but there was evidence for a delayed toxicity to IBA applied at this level. Pre-treatment with 2000 p.p.m. IBA is therefore recommended.Benomyl increased the percentage of rooted cuttings, but did not affect root length, possibly due to its fungicidal rather than cytokinin activity.     

Plum Rootstock Trials at East Malling

Summary

Dormant axillary buds excised from crowns of pineapple (Ananas comosus L., Merr.) cultured on growth regulator free Nitsch medium sprouted after 8–10 d. Sprouted buds produced multiple shoots (7–10 shoots per bud) upon transfer to solidified Murashige and Skoog medium supplemented with 9.67 μM NAA, 9.84 μM IBA and 9.29 μM KIN. Each isolated shoot upon subculture to liquid medium of the same composition further proliferated to form more multiple shoots (60–65 shoots) and were maintained on a gyratory shaker (90–100 rpm). In vitro grown shoots were rooted on White medium supplemented with 0.54 μM NAA and 1.97 μM IBA. In vitro plantlets were established in cups with soilrite and hardened for four weeks. Phenotypic variants such as albinos, white streaked shoots and shoots with elongated internodes were observed in in vitro cultures. Approximately 520 in vitro produced plantlets were established in the field and these plants exhibit somaclonal variation. Thirty-eight plants were found to be yellowish, spineless with anthocyanin streaks and three were anthocyanin rich, spined plants.     

Depressing Effects of Virus Infection on Adventitious Root Production in Apple Hardwood Cuttings

Adventitious rooting in dormant hardwood cuttings of MM. 106 apple rootstock was depressed by latent infection with five viruses, viz. rubbery wood, stem pitting, epinasty and decline, chlorotic leaf spot and platycarpa scaly bark viruses.

Both the number of rooted cuttings and the number of roots per rooted cutting were reduced, and fewer unrooted cuttings remained alive, thus representing a further potential loss.

The production of shoots suitable for use as cuttings was decreased from infected hedges, as was the ability of cuttings subsequently to become established and grow in the nursery.