Mycelis Muralis Research Articles

Effect of Selected Meteorological Variables on Full Flowering of Some Forest Herbs in the Western Carpathians

At present, temperate forest ecosystems are endangered by both abiotic and biotic factors. The effects of abiotic components, e.g., meteorological variables, are constantly studied. However, the detailed mechanisms affecting the phenology of plants are still unknown. Two meteorological variables (air temperature and cumulative precipitation) were analysed for the period from 1995 to 2020 in order to determine which factor which has a more significant effect on onset of the full-flowering (FF) phenophase. A set of nine forest herbs, representing different phenological groups from the viewpoint of flowering, was examined (early spring: Petasites albus and Pulmonaria officinalis; mid-spring: Carex pilosa and Dentaria bulbifera; late spring: Fragaria visa and Galium odoratum; early summer: Veronica officinalis; mid-summer: Mycelis muralis; and late summer: Campanula trachelium). Temperature-sum requirements and temporal trends in the onset of FF were also studied. The research conducted at the Ecological Experimental Station in the Kremnické vrchy Mountains (central Slovakia) at an altitude of 500 m asl. Our results show that the air temperature correlated more significantly with the date of onset of FF (r > 0.6, p < 0.001) than with precipitation. On average, the air-temperature sums, calculated for the threshold temperatures of 0 °C and 5 °C, increased from 142.9 °C (Petasites albus) to 1732.9 °C (Campanula trachelium) and from 223.4 °C (Petasites albus) to 1820.8 °C (Campanula trachelium), respectively. Temporal trends in the onset of FF over the last 26 years confirm shifts to earlier dates for most species (excepting early spring Petasites albus). In spring flowering species, shifts ranged from 2 days (0.07 day/year) for Pulmonaria officinalis to 8 days (0.30 day/year) for Carex pilosa. As for summer species, the onset of flowering shifted more significantly to earlier dates—from 7 days (0.27 day/year) for Campanula trachelium to 12 days (0.46 day/year) for Veronica officinalis. The observed trends were statistically significant (p < 0.05) for five examined species (Carex pilosa, Dentaria bulbifera, Fragaria vesca, Veronica officinalis and Mycelis muralis).

Неморальнотравные ельники Европейской России

The objectives of this paper are the reviewing nemoral herb spruce forests of European Russia (ER), elaborating diagnostic species combination, revealing species diversity, discussing syntaxonomical position, and validation of nemoral herb spruce forest syntaxa. The study concern 62 coenofloras (published and unpublished data from 11 regions of ER) and 448 rele­vés. The initial diagnosis of the association (Korotkov, Morozova, 1986; Zaugolnova, Morozova, 2004), origi­nally based on local and incomplete materials, was refined, as a result of the generalization of a vast literature and factual data. All nemoral herb spruce forests of ER belong to ass. Rhodobryo rosei–Piceetum abietis Korotkov 1986 (RP) with three subassociations: RP typicum, RP abietetosum sibiricae and RP caricetosum pilosae. The issues of syntaxonomic assignment of the association to the higher units are discussed. The position of association within the class Carpino-Fagetea, order Carpinetalia and alliance Querco-Tilion was justified by predominance of nemoral species in lower layers of communities. Diagnostic species of association (Picea abies (upper layer), Athyrium filix-femina, Circaea alpina, Daphne mezereum, Dryopteris expansa, Gymnocarpium dryopteris, Mycelis muralis, Oxalis acetosella, Phegopteris connectilis, Pyrola rotundifolia, Stellaria nemorum; Cirriphyllum piliferum, Plagiochila porelloides, Plagiomnium affine, P. medium, Rhodobryum roseum, Sciuro-hypnum starkei, S. curtum) are identified by fidelity index (Chytrý et al., 2002) and largely coincide with species of suballiance Tilio-Piceenion (Morozova, 2016). Alliance of Eastern European oak and lime tree forests Querco-Tilion is divided into two suballiances including proper deciduous forests (Querco-Tilienion) and spruce forests with nemoral herb and moss layers (Tilio-Piceenion), reflecting the zonal features of deciduous-coniferous forests in ER. The specific traits of the association communities are the species polydominance and total predominance of nemoral species in the lower layers. Thus, nemoral species can be considered as a collective dominant, with a cover approximately equal to or exceeding that of Oxalis acetosella (Vasilevich, Bibikova, 2004). Dominant species in the herb-subshrub layer vary not only due to the local conditions, but also to the age of forest stands. O. acetosella, as well as Aegopodium podagraria, Carex pilosa, Galeobdolon luteum, Galium odoratum, Mercurialis perennis, Pulmonaria obscura, Stellaria holostea, and some fern species can predominate. For subassociation, an ecological characteristics estimated by Ellenberg indicator scales (Ellenberg et al., 1991) are given. The floristic originality of syntaxa and the role of environmental factors are demonstrated by the method of nonlinear multidimensional scaling (NMDS). Differentiation of the internal structure of the association at the lower hierarchy levels is difficult, since these forests are a very polymorphic group regarding the dominating species. The predominance of one or combination of several species is related to speci­fic environments and can be identified at the level of the variants, which is reflected in development of regional classifications (Semenishchenkov, Kuzmenko, 2011; Morozova, Tikhonova, 2012; Semenishchenkov, 2012). The area of eastern European nemoral herb spruce forests covers the territory from the east of the Baltic countries to the Volga river. Communities of association represent a zonal type of vegetation in the broad-leaved coniferous subzone and southern half of the southern taiga, but are extrazonal both in the north and south of their distribution. These forests occur on moraine loamy plains: in the southern taiga — mainly on the tops and slopes of hills, while in the broad-leaved coniferous subzone — on well drained plains and ­gentle slopes. Subassociations are differentiated by their geographical location: RP typicum represents west and central nemoral herb spruce forests, RP abietetosum occurs in the north-east of association range and RP caricetosum — in the south. For the most distinctive subassociation RP abietetosum character are the presence of Abies sibirica, hydrophylous and some species of Siberian tall herbs, and a smaller proportion of nemoral species. The number of species in the coenofloras is not ­being changed on the latitudinal gradient, but the species richness of the communities, as well as the cover of the lower layers, decrease southwards. Perhaps this is due to the increased presence of hazel, which creates a pronounced level of the undergrowth in the RP caricetosum. The floristic comparison and proposed concept of the nemoral herb spruce forests syntaxonomy make the regional syntaxonomic units comparable in volume and allow to adequately outline the modern range of forests of this type in ER.

МЕСТОНАХОЖДЕНИЕ МИЦЕЛИСА СТЕННОГО НА ТЕРРИТОРИИ САРАТОВСКОЙ ОБЛАСТИ

МЕСТОНАХОЖДЕНИЕ МИЦЕЛИСА СТЕННОГО НА ТЕРРИТОРИИ САРАТОВСКОЙ ОБЛАСТИ

High concentrations of heavy metals in beech forest understory plants growing on waste heaps left by Zn-Pb ore mining

This study investigated (1) concentrations of pollutants such as As, Cd, Pb, Tl and Zn, as well as Ca, Fe and Mn, in soils developed on old heaps of waste rock localized in beech forests (2) concentrations of these elements in shoots and roots of forest herbaceous species – Mycelis muralis, Melica nutans and Mercurialis perennis, and in leaves of young Fagus sylvatica trees growing on the heaps (3) ratios of plant/soil and shoot/root concentrations to assess metal accumulation strategy of herb species. Total soil concentrations of all pollutants except Tl were high, up to 156mgAskg−1, 62.9mgCdkg−1, 2853mgPbkg−1, 3.6mgTlkg−1 and 13,508mgZnkg−1. Element concentrations in the tissues of herbaceous plants depended on plant species and organ (shoot vs. root). Cd, Pb, Tl and Zn, but not As, were elevated in both herb species and F. sylvatica in comparison to reference values, reaching up to 0.21mgAskg−1, 47.4mgPbkg−1 and 8.2mgTlkg−1 in roots of M. perennis, and 63.6mgCdkg−1 and 752mgZnkg−1 in roots of M. nutans. The efficiency of pollutant transfer from soil to roots and/or shoots varied among plant species and elements. Some heavy metals were effectively taken up from soil (Cd, Tl) or translocated to shoots (Cd, Zn), though it depended on plant species. Our study indicates a risk of the dispersion of heavy metals in the environment.

Impact of deer on temperate forest vegetation and woody debris as protection of forest regeneration against browsing

A 3-year field experiment with paired exclosure (fenced areas, excluding deer) and control plots (unfenced areas, free access to deer), with two treatments with and without woody debris, was carried out at two sites in a temperate forest in eastern France. The aim of the experiment was to assess the effect of browsing by roe deer ( Capreolus capreolus) and red deer ( Cervus elaphus) on the diversity and richness of plant species and to test the effectiveness of using woody debris to protect seedlings and saplings from deer browsing. In presence of deer, both plant species richness and diversity were reduced the first year of the study, but this negative impact of deer then disappeared after 3 years. Deer browsing mostly affected species composition of plant communities. We observed a decrease in the abundance of preferred species such as Carpinus betulus, Rubus fructicosus, Rubus idaeus, Anemone nemorosa and Epilobium angustifolium, and palatable species such as Acer spp., Carex spp., Festuca spp. and Mycelis muralis, whereas unpalatable species such as Lamium spp., or species particularly resilient to browsing such as grasses ( Brachypodium spp. and Luzula spp.) increased in abundance. The use of woody debris as protection against browsing by deer did not limit damage to seedlings and saplings of the main commercially valuable species, Abies alba and Quercus spp. Instead of limiting deer impact, use of woody debris seemed to increase the negative effect of deer browsing on regeneration in control plots relatively to those without protection.

Darwinism renewed: contemporary studies of plant adaptation

Darwinism renewed: contemporary studies of plant adaptation

Darwin's wind hypothesis: does it work for plant dispersal in fragmented habitats?

Using the wind-dispersed plant Mycelis muralis, we examined how landscape fragmentation affects variation in seed traits contributing to dispersal. Inverse terminal velocity (Vt(-1)) of field-collected achenes was used as a proxy for individual seed dispersal ability. We related this measure to different metrics of landscape connectivity, at two spatial scales: in a detailed analysis of eight landscapes in Spain and along a latitudinal gradient using 29 landscapes across three European regions. In the highly patchy Spanish landscapes, seed Vt(-1)increased significantly with increasing connectivity. A common garden experiment suggested that differences in Vt(-1) may be in part genetically based. The Vt(-1) was also found to increase with landscape occupancy, a coarser measure of connectivity, on a much broader (European) scale. Finally, Vt(-1)was found to increase along a south-north latitudinal gradient. Our results for M. muralis are consistent with 'Darwin's wind dispersal hypothesis' that high cost of dispersal may select for lower dispersal ability in fragmented landscapes, as well as with the 'leading edge hypothesis' that most recently colonized populations harbour more dispersive phenotypes.

Role of antioxidant systems in wild plant adaptation to salt stress

Wild plants differing in the strategies of adaptation to salinity were grown for six weeks in the phytotron and then subjected to salt stress (100 mM NaCl, 24 h). The activities of principal antioxidant enzymes and the accumulation of sodium ions and proline were studied. Independently of the level of constitutive salt tolerance, plants of all species tested accumulated sodium ions under salinity conditions but differed in their capability of stress-dependent proline accumulation and superoxide dismutase (SOD) and guaiacol-dependent peroxidase activities. Proline-accumulating species were found among both halophytes (Artemisia lerchiana and Thellungiella halophila) and glycophytes (Plantago major and Mycelis muralis). The high activities of ionically-bound and covalently bound peroxidases were characteristic of Th. halophila plants. High constitutive and stress-induced SOD activities were, as a rule, characteristic of glycophytes with the low constitutive proline level: Geum urbanum and Thalictrum aquilegifolium. Thus, a negative correlation was found between proline content and SOD activity in wild species tested; it was especially bright in the halophyte Th. halophila and glycophyte G. urbanum. An extremely high constitutive and stress-induced levels of proline and peroxidase activity in Th. halophila maybe compensate SOD low activity in this plant, and this contributed substantially into its salt resistance. Thus, monitoring of stress-dependent activities of some antioxidant enzymes and proline accumulation in wild plant species allowed a supposition of reciprocal interrelations between SOD activity and proline accumulation. It was also established that the high SOD activity is not obligatory trait of species salt tolerance. Moreover, plants with the high activity of peroxidase and active proline accumulation could acclimate to salts stress (100 mM NaCl, 24 h) independently of SOD activity.

Флористическая классификация лесов c Fagus orientalis Lypsky и Abies nordmanniana (Stev.) Spach в бассейне реки Белой (Западный Кавказ)

The area of the Belaya River basin (Western Cau­casus) within the altitudinal ranges of 700 to 2100 m is covered with beech-fir forests, composed of Fagus orientalis and Abies nordmanniana, which occur in slopes of various exposure and inclination. Syntaxo­nomic diversity of these communities is represented by four associations: 1. Sambuco nigrae—Fagetum orien­talis ass. nov.; the diagnostic species set includes Sam­bucus nigra, Symphytum grandiflorum, Pachy­phragma macrophyllum, Paris incompleta, Acer pseudoplatanus, Philadelphus caucasicus, Hedera helix; 2. Festuco dry­mejae—Abietetum nordmannianae ass. nov.; the diagnostic species are Festuca dry­meja, Sanicula europaea, Solidago virgaurea, Galium rotundifolium, Mycelis muralis, Lathyrus aureus, Calamintha grandiflora; 3. Rhododendro pontici—Fagetum orientalis ass. nov.; the diagnostic species is Rhododendron ponticum; 4. Petasito albae—Abietetum nordmannianae ass. nov.; the diagnostic species are Acer trautvetteri, Petasites albus, Symphytum asperum, Aconitum orientale, Adeno­styles macrophylla, Geranium sylvaticum, Myosotis amoena, Valeriana officinalis. The associations are subordinated to the alliance Abieti—Fagion orientalis Korotkov et Belonovskaja 1987 of the order Rhododendro pontici—Fagetalia orientalis Passarge 1981 and the class Querco-Fagetea Br.-Bl. et Vlieger 1937. The results, together with those obtained by Korotkov & Belonovskaya (1987), allow us to assume that all the dark coniferous forest units of the Caucasus Range could be included into this single alliance.

Scree forests (Mercuriali-Tilietum) of the Börzsöny Mountains, Hungary

Scree forest communities Mercuriali-Tilietum Zolyomi et Jakucs 1958 of Borzsony Mts were not processed until the present. These lime-dominated forests develop on andesite base-rock, mainly on periglacial scree surfaces. Using the Braun-Blanquet-Soo method 15 sampling spots were studied and analysed based on floristical composition, cenological aspects and habitat characteristics. The stand's species stock consists of tree species like Acer platanoides, Carpinus betulus, Fraxinus excelsior, Tilia platyphyllos, shrubs like Cornus mas, Corylus avellana, Euonymus verrucosus, Ribes uva-crispa and herbs like Cystopteris fragilis, Dryopteris filix-mas, Galeobdolon luteum, Galium schultesii, G. odoratum, Hedera helix, Melica uniflora, Mercurialis perennis, Mycelis muralis, Poa nemoralis, Waldsteinia geoides. Rare Tilio-Acerion species are Adoxa moschatellina, Gagea minima, Geranium lucidum. Cenological categories, life forms, geoelement distribution, and Borhidi's Social Behaviour Types were studied on the basis ...

Interspecific variation in soil compaction sensitivity among forest floor species

The present study aimed at exploring the response of herbaceous plant species to soil compaction in forest soils. The research was conducted in central Belgium, in a 4383 ha beech forest. Of the 107 taxa studied, the cover of 65 species (61%) was significantly related to soil compaction. Twenty four forest species (58% of all forest species tested) showed significant growth responses to soil compaction. A few, such as Carex strigosa, Epilobium montanum and Mycelis muralis, showed monotonic reduction in growth with increasing compaction, but about half showed a bell-like response with maximum growth at 200 N ( Hyacinthoides non-scripta) or 400 N (e.g., Carex pilulifera, Melica uniflora) or even 600 N ( Oreopteris limbosperma). Only four species ( Carex remota, C. sylvatica, Rumex sanguineus, Veronica montana) showed positive growth responses with increasing compaction, up to 1200 N. This contrasts with non-forest species where 18 out of 41 showed high tolerance to heavily compacted soils (e.g., Geum urbanum, Glechoma hederacea, Impatiens parviflora, Polygonum hydropiper, Veronica serpyllifolia). The sensitivity of forest species has obvious implications for both conservation and management. The practical measures for long-term conservation of forest herbs are discussed.

Survival on the Exposed Limestone Pavement in the Burren: Photosynthesis and Water Relations of Three Co–Occurring Plant Species

Examination of the abundance of plant species occurring in limestone terrain at Mullagh More, in the Burren, Co. Clare, indicates that 'shade' plants are not restricted to microenvironmental conditions with reduced light levels (grikes), but are also common in exposed situations. Investigations of three species found in exposed locations (Teucrium scorodonia L., Mycelis muralis L. Dumort. and Corrylus avellana L.) indicate that they all have a limited capacity to acclimate their maximum photosynthetic rate (Pm) to the prevailing light climate and that as much as 70% of the incident irradiance is not utilised in photosynthesis. Diurnal reductions in stomatal conductance (Gs) and maximum photosynthetic rate (P,,), were observed with all three species. These changes in Pm and Gs were associated with concomitant decreases in shoot water potential (TP) and increases in leaf-air vapour pressure deficit (VPD), suggesting that water availability could be an important factor even under the prevailing mild climatic conditions. This was supported by parallel species-specific declines in the ratio of variable (Fv) to maximum (Fm) fluorescence (F,/F,Qj for a larger number of species found in these limestone habitats. Shoot-water status was also closely coupled to short-term wetting and drying episodes caused by periodic rainfall events. On the basis of this evidence, water limitation is likely to be a common and overriding ecological determinant in this limestone environment, despite the mild climatic conditions. Also, under these environmental conditions a limited acclimatory capacity does not preclude an ability to persist in exposed situations. Bruce Osborne (corresponding author; email: Bruce.Osborne@ucd.ie.),

The Effects of Winter Exposure to Acid Soil Conditions on the Subsequent Survival and Growth of Herbaceous, Forest Perennials: a Preliminary Investigation

For many plant species, growth is limited in acid soils, which are characterized by high levels of potentially-toxic elements and low nutrient availability. Although plant-soil interactions are traditionally studied during the growing season, the highest concentrations of toxic elements in the soil may occur during the winter months. The present study investigated the effects of a 3-month exposure to either an acid or a reference soil, at temperatures fluctuating around freezing point, on subsequent survival and growth of eight herbs (Brachypodium sylvaticum, Carex pilulifera, Geum urbanum, Luzula pilosa, Mycelis muralis, Silene dioica, Stellaria nemorum, Veronica officinalis).The plants were exposed to ambient weather conditions from December to March, after which they were replanted in fresh reference soil and transferred to a glasshouse. Their biomass was measured 5 weeks later. The plant species differed in their responses to the soils, in a manner reflecting their natural field distributions. All plants of the most acid-tolerant species survived in both treatments, whereas the more sensitive species showed lower survival rates after growth in the acid than in the reference soil. Similar results were found for the regrowth:C. piluliferaandL. pilosa, the most acid-tolerant species, were unaffected by the soil treatments (ratios between biomass in acid compared to reference soils were 0.8 and 1.1, respectively), whereasG. urbanum, M. muralis, S. nemorumandV. officinaliswere negatively affected (ratios 0.3–0.5). Effects on above- and below-ground biomass were broadly similar. This preliminary evidence indicates that soil chemistry during the winter can be important for both survival and growth during the vegetative period that follows.

Irradiance and nitrate‐dependent variation in growth and biomass allocation of Mycelis muralis. An analysis of its significance for a functional categorization of ‘sun’ and ‘shade’ plants

summaryThe biomass of Mycelis muralis (L.) Dumort plants increased with increases in growth irradiance and nitrate supply. Comparisons of the data from this study with published information indicate that biomass production and growth rate of M. muralis are comparable to that of a number of slow‐growing species from resource‐poor environments. Biomass allocation varied with growth irradiance and nitrate supply. At high irradiances and low nitrate supplies there was a significantly greater allocation of plant mass to roots, resulting in a lower leaf area ratio (LAR) and leaf mass ratio (LMR). In contrast to the findings of a number of other studies, light level and nitrate supply had interactive effects on leaf mass per unit area (LMA). Changes in LAR due to variations in irradiance were mainly a consequence of changes in LMR. Given the ability of M. muralis to grow in deep shade, this suggests that large changes to within‐leaf allocation (LMA) are not an essential requirement for growth at low irradiances. Conversely, because M. muralis can also grow in fully exposed situations, these traits might not exclude some shade species from high irradiance habitats. However, a low growth rate, or traits which result in a low growth rate, might be advantageous in a number of resource‐poor environments.

Is acclimation required for success in high light environments? A case study using Mycelis muralis (L.) Dumort (Asteraceae).

In the field significant differences in maximum photosynthetic O2 -exchange rate (Pm ) were found between leaves of Mycelis muralis (L.) Dumort (Asteraceae) collected from woodland and exposed habitats, with the highest values in the exposed sites- However, there were no differences in the Pm of leaves collected from plants growing in grikes (fissures in the limestone pavement), of exposed limestone pavement, despite a greater than four-fold difference in the integrated daily irradiance. Leaves of plants from the open pavement had lower photon yields (ø1 ) and higher dark respiration rates and light compensation points, in comparison to shaded plants. Under controlled environmental conditions the highest Pm of leaves from plants subjected to variations in irradiance were found at the intermediate (8-6 mol photon m-2 d-1 growth light level used. At the highest growth irradiance 17.3 mol photon m-2 d-1 used in the laboratory both Pm and øl were reduced, although the latest plant biomass was found at this irradiance. No changes were found in the chlorophyll a:b ratio over the same range of irradiances. Examination of plant populations of M. muralis, collected from open or shaded habitats and exposed to growth irradiances that covered the range over which increases in photosynthesis were, observed in the laboratory (0.86-8.6 mol photon m-2 d-1 ), resulted in changes in leaf structure and pigment composition. The chlorophyll a:b ratio was low and largely independent of irradiance or the origin of the plant population. Differences in total chlorophyll content were small with the lowest values m the Durrow woodland populations at both irradiances. No variations were found in a number of chloroplast thylakoid structural features. In particular, the ratio of oppressed to non-appressed membranes was unchanged by growth at the two irradiances, consistent with an invariant chlorophyll a:b ratio. Based on peaks in the difference spectra the woodland populations had mi enhanced in vivo absorption at λlD= 650 and 706 nm when grown at low irradiance. These peaks were absent from the population collected from the open limestone pavement. The significance of the enhanced absorption at low irradiance and the possibility that these peaks represent long-wavelength forms of chlorophyll a (λlD = 706) and b (λlD = 650) is discussed. A particular feature of plants grown at high irradiance was an enhanced anthocyanin content in comparison to those grown at low irradiance. This was associated with an increase in absorptance. particularly in the green region (λlD = 550 nm) of the visible spectrum. Overall these results suggest that complete acclimation of photosynthesis and an ability to modulate light-harvesting is not a prerequisite, for success in a high light environment.

Evaluation of wild Lactuca species for resistance of natural infection of powdery mildew (Erysiphe cichoracearum)

The 99 accessions of seven wild Lactuca species (L. serriola, L. saligna, L. virosa, L. viminea, L. perennis, L. tenerrima, L. tatarica) and Mycelis muralis (syn. L. muralis) were tested for natural infection of Erysiphe cichoracearum L. serriola accessions were highly susceptible. L. saligna showed highly variable levels of resistance. Other Lactuca species were mostly resistant or only moderately susceptible.

Further Investigation of the Specificity of Interactions Between Wild Lactuca spp. and Bremia lactucae Isolates from Lactuca serriola

AbstractSpecificity of interactions between eight Lactuca species (L. saligna, L. virosa, L. altaica, L. dregeana, L. perennis, L. tenerrima, L. tatarica, L. viminea) and two related genera (Mycelis muralis, Chondrilla juncea) and seven Bremia lactucae isolates from Lactuca serriola was studied in 96 accessions. The 35 L. saligna accessions gave no evidence for race‐specificity and a non‐host resistance is expected. L. virosa (36 accessions) showed a highly various response. A substantial part of the studied sets expressed a race‐specific resistance. L. altaica (one accession), which is closely related to L. serriola, was susceptible to all isolates used. L. dregeana (2 accessions) showed also a race‐specific response. The accessions of L. perennis (7), L. tatarica (2) and L. viminea (1) were resistant. The susceptibility of L. tenerrima (3 accessions), which is related to L. perennis, is unexpected. In Mycelis muralis (8 accessions) very often a incomplete resistance was observed. Chondrilla juncea (1 accession) was resistant to all isolates used. It can be concluded that the genetic distances between species cannot be used as a prediction for resistance or susceptibility.

MODELS FOR THE CONTROL OF BRANCH POSITIONS AND FLOWERING SEQUENCES OF CAPITULA IN MYCELIS MURALIS (L.) DUMONT (COMPOSITAE)

SummaryThe development of highly branched inflorescences is considered. Two main characteristics of these structures are the flowering sequences (acropetal, basipetal or divergent) and the branch production (acrotonic, basitonic or mesotonic), which can be different on various branching orders (paracladia). A widespread pattern, found especially among Compositae, is a basipetal or divergent flowering sequence combined with basitonic or mesotonic branch production. We present quantitative models for this type of inflorescence development, based on the transport of a flower‐inducing hormone (florigen) and of a hormone responsible for apical dominance (auxin), together with some additional control factors. The computed structures obtained with these models are compared with observations on the inflorescence development of wall lettuce, Mycelis muralis.