Resprouting after disturbance: an experimental study with short-lived monocarpic herbs

We experimentally demonstrated the ability of three short-lived monocarpic species to vegetatively regenerate (resprout) from roots after severe disturbance. We assessed the relationship between resprouting ability and (1) timing of injury with respect to life-cycle stage (reproductive vs. vegetative plant), life-history mode (annual vs. winter annual) and phenological stage (flowering vs. fruiting plant), (2) nutrient availability, and (3) disturbance severity (removal of all axillary buds Yes/No). In a chamber experiment with the annual or potentially winter annualRorippa palustris, all injured plants resprouted in all nutrient levels and day-length regimes (day-length regimes simulated conditions of an annual and a winter annual cohort). The number of adventitious buds on roots was positively affected only by injury. The extent of regeneration and amount of regenerated biomass were higher at high nutrient level and long-day regime.     

Compensation of seed production after severe injury in the short-lived herb Barbarea vulgaris

A pot experiment with the common ruderal herb Barbarea vulgaris (Brassicaceae) was set up to elucidate to what extent short-lived species sprouting from roots regenerate and compensate for seed production after damage. We tested if sprouting from roots ensures survival after severe aboveground biomass damage, but the number of seeds produced declines with increasing severity of injury, decreasing nutrient availability and progress in the life cycle at the time of injury.Plants of B. vulgaris were cultivated in a 3-year garden experiment at two nutrient levels (high vs. low). During the experiment, two levels of injury severity were applied: high (removal of all aboveground biomass) and low (removal of aboveground biomass leaving basal axillary buds intact). Damage was applied at four life-cycle phases: young rosette, overwintered rosette, flowering plant and fruiting plant. All injured plants survived and resprouted irrespective of life-cycle phase, severity of injury and nutrient availability. Injury significantly affected seed production and also the plants’ life cycle. Plants injured in the second year of their life (overwintered rosette, flowering plant and fruiting plant) postponed reproduction to the third season (in the case of high injury severity) or their seed production was lower than in intact plants (in the case of low injury severity). In plants injured in the first life year, seed production and life cycle were not influenced. Nutrient level only marginally affected resprouting after injury and seed production.The experiment showed that the ability to sprout from roots enables plants to survive a 100% loss of aboveground biomass, and to keep some seed production or even compensate it. The short-lived ruderal species B. vulgaris successfully copes with severe disturbance by resprouting and does not rely only on its seed bank.     

Vegetative regeneration of biennial Oenothera species after disturbance: Field observations and experiment

It has been recently shown that some annual and biennial species of man-made habitats cope with severe disturbance by resprouting (vegetative regeneration) from their bud bank and do not only rely on regeneration from seeds. Nevertheless, information on the ecology of this phenomenon is rare. In a field study, we answered the question how frequent is resprouting from root buds in populations of the ruderal biennial herb Oenothera biennis, and how it is affected by habitat conditions. In an experiment, we tested the hypothesis that higher severity of injury and later life-cycle phase of the injured plants suppress resprouting from both axillary and root buds in O. biennis and also in its closely related congeners O. fallax and O. glazioviana.In 25 out of 29 studied ruderal populations of O. biennis severely injured individuals were found; however, only half of these populations included injured individuals that resprouted from roots. Among these populations, the number of root-sprouting individuals varied highly (from 3% to 67% of injured individuals). The largest populations and the highest percentage of root-resprouting individuals were found in urban habitats with sandy/gravelly substrate, a low vegetation cover, and a high frequency of disturbance.In the experiment with three Oenothera congeners, removal of aboveground biomass with all axillary buds largely led to the death of plants of all three species. When a portion of the basal axillary buds remained intact, individuals of O. biennis mostly failed to regenerate, whereas individuals of O. fallax and O. glazioviana survived and formed seeds. A higher severity of injury suppressed resprouting in Oenothera congeners in this experiment. However, the relationship between life-cycle phase and the ability to resprout remains unclear in Oenothera species.This study showed that resprouting after severe injury is an important feature of Oenothera individuals occurring in man-made habitats and may represent an alternative strategy to regeneration from the seed bank under disturbance conditions.     

Bud structure and resprouting in coppiced stools of Salix viminalis L., S. eriocephala Michx., and S. amygdaloides Anders

Fast-growing willows are cultivated as coppice in short rotation biomass plantations. The production and sustainability of the system is based on the ability of trees to resprout after repeated harvesting. The large variation in coppicing ability is due to plant genotypic differences in structure and physiology as well as environmental factors. Morphological and structural prerequisites for resprouting were compared in two shrubby willows with high coppicing ability, S. viminalis and S. eriocephala, and one tree-formed species, S. amygdaloides, with low coppicing ability. The initiation and development of buds and the resprouting pattern of coppiced stools were compared. All buds were axillary in origin and showed the same principal structure consisting of one main shoot primordium and two lateral primordia. In S. viminalis and S. eriocephala the lateral buds contained several leaf primordia and sprouted shortly after the main bud. In S. amygdaloides further development of lateral buds was inhibited after formation of two budscales, and leaf primordia were not formed until the buds were forced to sprout. The number of sprouts developing after coppicing were correlated to the structure and number of buds and their position on the stools. Self-thinning rate was high and many shoots originating from lateral buds died. Most buds were located above ground on the remaining basal portions of harvested stems. No adventitious buds were found on the stools. Significantly different bud differentiation pattern and frequent sylleptic sprouting resulted in lower coppice response in S. amygdaloides compared to S. viminalis and S. eriocephala.     

Secondary buds in Scots pine trees infested with <Emphasis Type="Italic">Gremmeniella abietina</Emphasis>

In winter 2000–2001, there was a serious outbreak of Gremmeniella abietina Morelet in southeastern Norway. During the outbreak, we noted that injured Scots pine trees (Pinus sylvestris L.) developed secondary buds in response to the fungus attack, and we decided to study the relationship between injury, appearance of secondary buds and recovery of the trees thereafter. For this purpose, 143 trees from 10 to 50 years of age were chosen and grouped into crown density classes. Injury was assessed in detail, and buds were counted before bud burst in the spring of 2002. In addition, a subset of 15 trees was followed through the summer of 2002 to assess recovery. All injured trees developed secondary buds, with a clear overweight of dormant winter buds in proportion to interfoliar buds. Healthy control trees did not develop secondary buds at all. The secondary buds appeared predominantly on the injured parts of the tree; interfoliar buds in particular developed just beneath the damaged tissue. Most of the secondary buds died during the winter of 2001–2002, mainly because the fungus continued to spread after the first outbreak. Many of the remaining buds developed shoots with abnormal growth during the summer. Secondary buds may help trees to recover from Gremmeniella attacks, but this strategy may fail when the fungus continues to grow and injure the newly formed buds and shoots.     

Life-history variation in the short-lived herb <Emphasis Type="Italic">Rorippa palustris</Emphasis>: effect of germination date and injury timing

Life-history variation in annuals is known to be caused by size requirements for photoinduction of flowering, but the importance of germination date and injury was overlooked so far even though they may play an important role in disturbed habitats. To test the effect of germination date and timing of injury on life-history variation of an annual plant, we performed a 2-year pot experiment with the root-sprouting herb Rorippa palustris. Plants belonging to six different cohorts, and sown at monthly intervals from April to September, were injured (all stem parts removed) in three ontogenetic stages: vegetative rosettes, flowering plants and fruiting plants. Plants from the April, and partly from the May, cohort behaved as summer annuals: they started to bolt at the same time, resprouted and overwintered poorly. Plants from the June cohort flowered in the first season as well, but they entered the bolting stage a month later than the preceding cohorts, produced the least fruits, but overwintered successfully and flowered again the second year (polycarpic perennials). Cohorts germinating after the summer solstice did not flower during the first year and, with the exception of the September cohort, overwintered successfully and flowered the second year (winter annuals). After injury, the pattern of life-histories was the same as in control plants, although generative reproduction was interrupted by injury in the first year of the experiment. About one quarter of␣plants injured in the vegetative stage regenerated after injury irrespective of cohort, however, regeneration was enhanced in larger plants. Regeneration of plants in the flowering and fruiting stages depended on date of injury in relation to day length, being the most successful after the summer solstice. Life-history variation, together with the ability to resprout after severe injury in the pioneer wetland herb Rorippa palustris is caused by its ability to germinate throughout the season. Even the second tested factor, the effect of injury, is modified by germination time. The experiment points to a complex nature of factors affecting life-history variation as well as resprouting after severe injury in short lived plants. An erratum to this article can be found at     

Action spectrum for light-induced formation of adventitious shoots in hairy roots of horseradish

An action spectrum was determined for lightinduced formation of adventitious shoots in hairy roots of horseradish (Armoracia rusticana Gaert., Mey. et Scherb.) cultured in vitro. Near ultraviolet (350–400 nm), blue (440–460 nm) and red light (600–680 nm) were most effective in inducing formation of adventitious buds. Farred light (730 nm) inhibited the promotive effect of all three wavelength regions. These results are consistent with induction by phytochrome(s) of adventitious shoots in hairy roots of horseradish.     

Plant regeneration via direct embryo axis-like shoot and root formation from excised cotyledon explants of ginseng seedlings

Summary Cotyledon explants of Panax ginseng at various developmental stages were cultured on Murashige and Skoog (MS) medium with 0.5 μM indole butyric acid and 8.8 μM N⁶-benzyladenine. Upon culturing of cotyledon explants from mature zygotic embryos, 34% of the explants formed somatic embryos, and 46% formed adventitious shoots. In the cotyledon explants from 1-wk-old seedlings, embryo axis-like shoots and roots developed at a high frequency (79%) near the excised portion of the cotyledon base. The developmental pattern of embryo axis-like organ formation was structurally different from that of somatic embryos and adventitious shoots but similar to that of parts of the embryo axis of zygotic embryos. In the early stages of embryo axis-like organ formation, epicotyl-like shoot primordia were developed directly from the cotyledon base after 2 wk of culture; subsequently roots developed near the base of the epicotyl-like shoots and eventually regenerated into plantlets with both shoots and roots. The frequency of embryo axis-like organ formation declined as the growth of seedlings proceeded. In addition, the frequency of somatic embryo and adventitious bud formation rapidly declined with the age of the cotyledons. Plant regeneration via embryo axis-like organ formation might be a new pattern of morphogenesis in P. ginseng cotyledon culture.     

紫茉莉不定芽诱导和植株再生

紫茉莉(Mirabilis jalapa)观赏价值较高,是一种重要的污染修复植物.组织培养技术为植物品种改良和选育的重要途径,但紫茉莉离体快繁方面的研究尚未见有相关报道.该研究以紫茉莉叶片和茎段为外植体,通过观察和统计外植体愈伤组织和不定芽的诱导情况,分析不同植物生长物质对紫茉莉植株再生的影响.结果表明:紫茉莉带芽茎段比较适合丛生芽的诱导,当带芽茎段在MS+1.0 mg·L-16-BA+1.5 mg·L-1 KT+1.0 mg·L-1 NAA+0.05 mg·L-1 TDZ培养基中培养时,不定芽的增殖系数较高.无论是MS或1/2MS培养基,都可诱导不定根的产生,其中生根效果较好的培养基为1/2 MS+0.5 mg·L-1 NAA.该研究结果探索了紫茉莉组织培养的最适条件,根据愈伤组织诱导率和不定芽的增殖系数筛选出了适宜不定芽诱导的培养基类型,根据不定芽生根情况确定了最佳的生根诱导培养基,为建立紫茉莉高效稳定的再生和遗传转化体系奠定了基础.     

Resprouting ability of<Emphasis Type="Italic"> Quercus crispula</Emphasis> seedlings depends on the vegetation cover of their microhabitats

To examine the effects of vegetation cover on the resprouting abilities of Quercus crispula seedlings, in each of three consecutive years, we artificially clipped seedlings growing in microhabitats with differing degrees of vegetation cover. We also investigated the relationship between the level of total nonstructural carbohydrate (TNC) and resprouting ability. Seedlings with clipped shoots in gaps produced larger resprouting shoots than those in the understory. Moreover, both the percentage of resprouting seedlings and the survival ratio in seedlings with clipped shoots were negatively correlated with the degree of vegetation cover. Seedlings stored high levels of TNC, especially in their roots, and their TNC levels were negatively correlated with the degree of vegetation cover. There were also positive relationships between the TNC levels in their roots and the degree of resprouting. Hence, we conclude that release from vegetation cover enhanced the resprouting ability of Q. crispula seedlings by increasing their levels of stored carbohydrate. The key variables affected were the resprouting ratio (the proportion of seedlings capable of producing new shoots) and the size of the resprouted shoots.     

Occurrence of adventitious sprouting in short-lived monocarpic herbs: a field study of 22 weedy species

Background and Aims

Adventitious sprouting from the hypocotyle and roots in monocarpic herbs has been confirmed in previous experimental studies as a means to avoid bud limitation after severe injury in annual and biennial plants. Data regarding the role of adventitious sprouting in natural populations, however, were lacking. The aim of the present study was to assess whether adventitious sprouting occurs in natural populations and how it is affected by plant size, plant injury, plant cover and environmental characteristics.

Methods

Data were sampled from 14 037 individual plants from 389 populations belonging to 22 annual and biennial species. Growth parameters were measured in individual plants, species composition and plant cover in communities were evaluated, and environmental characteristics were estimated using Ellenberg indicator values.

Key Results

It was confirmed that adventitious sprouting occurs in natural populations of all but five species examined. Adventitious sprouting was positively affected by plant size and plant injury. Environmental factors including availability of soil nitrogen were not shown to affect adventitious sprouting. Annual and biennial plants did not differ in sprouting, but upright annuals had a lower number of and longer adventitious shoots than prostrate annuals.

Conclusions

Adventitious bud formation is used to overcome meristem limitation when stem parts are lost due to injury, and thus resprouting in short-lived monocarps should not be overlooked.     

VEGETATIVE REGROWTH FOLLOWING CUTTING IN THE SHRUB BACCHARIS PILULARIS SSP. CONSANGUINEA (DC) C. B. WOLF

The resprouting ability following cutting of the chaparral shrub Baccharis pilularis ssp. consanguinea (DC) C. B. Wolf was investigated following the felling of individuals of various ages. Numbers of resprouts and resprout biomass were low in 1-yr-old shrubs, increased to a maximum in shrubs 3–4 yr old, and declined to zero in shrubs <8 yr old. Numbers of leaves produced were also lower in 1-yr-old shrubs. The results are interpreted on the basis of the internal origin of resprout buds and the increasing extent of the shrub's root system as it matures.     

Plant regeneration via organogenesis from adventitious bud explants of a medicinal herb species, <Emphasis Type="Italic">Polygonatum cyrtonema</Emphasis>

Summary Explants derived from adventitious buds, rhizomes, stems, and leaves of a medicinal plant, Polygonatum cyrtonema, were studied for plantlet regeneration, and only adventitious bud explants were able to be regenerated into plantlets. Regeneration was also accompanied by the formation of rhizome-like tissue, the medicinal portion of the plant. The optimum hormone combination for plantlet regenertion was 4.44 μM benzyladenine plus 2.26 μM 2,4-dichlorophenoxyacetic acid, at which new adventitious buds were obtained from 96.6% of the adventitious bud explants, with an average of 5.2 buds per explant. The best medium for root induction was half-strength Murashige and Skoog medium with 4.57 μM α-naphthaleneacetic acid, as 92% of regenerated buds rooted. Regenerated plantlets were successfully transferred to a greenhouse with 86% survival. Histological observation indicated that new adventitious buds originated from the superficial meristematic cell cluster of the granular callus induced from adventitious bud explants via organogenesis.     

禿杉组织培养研究

本文详细报道了从秃杉(Taiwania flousiana Gaussen)离体胚诱导不定芽、不定根及从无菌苗茎端培养再生植株的过程。诱导不定芽要求较低的蔗糖浓度(以3％最好);同时BA是必须的,在附加0.1—3 mg/1 BA的White培养基上,从离体胚的子叶或胚轴上诱导了不定芽的发生(以1 mg/1最好);NAA与BA结合使用,对不定芽诱导无促进作用;适当提高光照有利于不定芽的诱导。在诱导不定芽的同时,在子叶表面还观察到有许多无结构的“不定突起”。不定芽起源于子叶表皮下1—2层细胞。IBA对诱导离体胚上产生不定根效果较好。在有或无生长素的培养基上,从生长1月龄的无菌苗茎端培养获得了不定根的产生,在加有细胞分裂索的培养基上,从无菌苗上产生了腋芽。     

The relative importance of carbohydrate and nitrogen for the resprouting ability of Quercus crispula seedlings

BACKGROUND AND AIMS: Plants need some kind of stored resources to resprout after shoot destruction. The aim of this study was to determine the relative importance of carbohydrate and nitrogen (N) storage levels for their ability to resprout. METHODS: A shoot clipping experiment was conducted on Quercus crispula seedlings, which were grown in a factorial experimental design, with two light levels (40% and 3% of full light) and three nutrient concentrations (low, medium and high). KEY RESULTS: At the time of shoot clipping (the end of spring leaf expansion), seedlings exposed to 40% light had an average total non-structural carbohydrate (TNC) concentration of 17.0% in their roots compared with 4.9% in the roots of seedlings exposed to 3% light, and the average amount of TNC (TNC pools) in the roots was 203.8 mg and 20.0 mg at 40% light and 3% light, respectively. In contrast, root N concentration averaged 2.3% in the 3% light treatment compared with 1.2% in the 40% light treatment, and it increased with successive rises in nutrient concentrations at both light levels. Regardless of the nutrient status, at the 40% light level >80% of the seedlings resprouted after shoot clipping. Few seedlings, however, resprouted at the 3% light level, particularly in the medium- and high-nutrient treatments. Furthermore, both root TNC concentrations and TNC pools decreased after resprouting, but the amount of root N remained constant. CONCLUSIONS: These results suggest that carbohydrate storage has a stronger influence on resprouting in Quercus crispula than N storage. However, the size of the resprouting shoot was positively correlated with the amount of both N and TNC in roots. The level of N storage is, therefore, also important for the growth of resprouting shoots.     

濒危物种胡杨和灰叶胡杨的克隆生长特征

研究不同生态环境条件下胡杨和灰叶胡杨横走侧根的空间分布及其形态特征、不定芽及克隆分株的数量格局特征及其与土壤水分的关系。研究结果表明:(1)16团3个生境中灰叶胡杨克隆分株所在横走侧根均分布在10—20cm的土层;阿瓦提混交林内灰叶胡杨和胡杨克隆分株所在横走侧根分布在20—40cm的土层;轮台县河道边胡杨克隆分株所在横走侧根分布在10—20cm的土层,林内胡杨克隆分株所在横走侧根分布在20—40cm的土层。不定芽、克隆分株所在部位横走侧根最粗,向两端逐渐变细,且远端根始终比近端根要粗;(2)不定芽具有以前期克隆分株为中心向两端延伸发生分布的空间格局特征,横走侧根上不定芽数与出土克隆分株数呈极显著正相关,未出土克隆分株数与出土克隆分株数呈显著正相关,说明不定芽、未出土克隆分株的数量都直接影响出土克隆分株的数量。(3)不定芽、未出土克隆分株和出土克隆分株出现频率、空间分布范围在同一生境同一根段均表现为不定芽未出土克隆分株出土克隆分株,在不同研究区表现为16团(地下水位1.08m)轮台县(地下水位2.56m)阿瓦提县(地下水位3.34m);相关分析显示土壤水分含量与不定芽和出土克隆分株数量均呈极显著正相关。综合分析认为,地下水位和土壤含水量均对不定芽发生以及不定芽向克隆分株转化有显著的影响。     

Fitness of resprouters versus seeders in relation to nutrient availability in two Plantago species

Two contrasting strategies of plants from disturbed areas are reported to depend on nutrient availability. Resprouters, investing into storage and capable of vegetative regeneration after disturbance, are predicted to be enhanced in nutrient poor environments. This contrasts to seeders, which invest preferentially into seed production and regenerating only from seeds, and are thought to prevail in nutrient rich environments. To test such predicted dichotomy, we set up an experiment with two facultative resprouters with contrasting nutrient demands and assessed the fitness of individuals regenerated from seeds and root fragments in differently productive environments. We hypothesized that 1) plants with higher nutrient demands have a higher fitness as seeders irrespectable of nutrient availability and/or 2) both species will have a higher fitness as resprouters under lower nutrient availability and as seeders when nutrient availability is higher. Nutrient availability was also manipulated prior to and after disturbance to evaluate the impact of changing nutrient availability on the strategy of resprouting. The results of our pot experiment with Plantago lanceolata and Plantago media supported the first but not the second hypothesis. Moreover, high nutrient availability prior to disturbance negatively affected resprouting success, but the growth and fitness of successfully regenerated individuals were enhanced under higher nutrient availability. We concluded that resprouting from roots after disturbance is affected by nutrient availability, but this effect considerably differs between individual life-history stages.     

Plant regeneration from tissue cultures of Persian buttercup (Ranunculus asiaticus L.)

Different plant explants of Persian buttercup (Ranunculus asiaticus L.) were screened for callus induction and adventitious shoot regeneration on different media to establish totipotent cultures. Murashige & Skoog (MS) medium was used, supplemented with different concentrations of the following growth regulators: kinetin, benzyladenine (BA), naphthaleneacetic acid (NAA) and indoleacetic acid (IAA). Callus was induced and adventitious buds regenerated only from cotyledonary explants after 4–5 weeks. Subculture of the regenerated buds on the same basal medium in presence of gibberellic acid (GA₃) and BA produced well-organized shoots. Rooting was obtained by transferring shoots to growth regulator-free MS medium. A high rate of shoot multiplication has been achieved on medium with high concentration of kinetin and long-day photoperiod. Finally the plants were successfully transferred to soil and grown in a greenhouse.     

An investigation of morphogenesis within the genus Trifolium

Morphogenic responses within the genus Trifolium were investigated by culturing various explants from seedlings of 72 species. Seedlings from 32 species produced callus alone, 40 produced adventitious shoots and/or roots, of which 25 species produced only shoots and 7 species formed only roots. Seedlings within each species also varied in their response to culture. The section of these seedlings most likely to produce adventitious shoots was the original shoot with the remnants of the surrounding hypocotyl and cotyledons, followed by the excised cotyledons themselves.Inter- and intra-varietal variation was observed in T. repens. Genotypes that produced adventitious buds were selected and crossed. An improvement in the proportion of the population capable of morphogenesis was observed in one cultivar.