Importance of organic phosphate hydrolyzed in stalks of the lotic diatom <Emphasis Type="Italic">Didymosphenia geminata</Emphasis> and the possible impact of atmospheric and climatic changes

The aquatic colonial stalked diatom, Didymosphenia geminata, has acquired notoriety in recent years because of huge increases in many rivers of temperate regions. However, in some streams in northern England it has probably or, in the case of the R. Coquet (Northumberland), certainly been abundant for many decades. The paper describes the nutrient environment and phosphatase activities of Didymosphenia in Stony Gill (N. Yorkshire), a fast-flowing stream draining an upland catchment with peaty soils overlying limestone. Organic phosphate formed 85% of the filtrable phosphate in the water during the study (January–August 2000), with a maximum in April. Colonies were most abundant in June, but had disappeared by August. Surface phosphomonoesterase (PMEase) and phosphodiesterase activities assayed from March to July showed low PMEase activity in early March, but otherwise both were high throughout the period and especially so in June and July. Use of BCIP-NBT staining procedure showed that PMEase activity occurred in the stalks. A more detailed study of colony structure and staining with material from the R. Coquet in June 2006 also showed marked PMEase activity, with staining localized in the upper part of the stalks and the cells remaining unstained. It is suggested that organic phosphate is hydrolyzed in the stalk and the inorganic phosphate passes to the cell via a central tube in the stalk. It seems likely that organic phosphate as a major P source is a key factor favouring the success of Didymosphenia. The possible impact of environmental changes in the catchment such as climatic warming, C loss from peat and atmospheric N deposition is discussed. Handling editor: L. Naselli-Flores     

Rhopalia are integrated parts of the central nervous system in box jellyfish

In cubomedusae, the central nervous system (CNS) is found both in the bell (the ring nerve) and in the four eye-bearing sensory structures (the rhopalia). The ring nerve and the rhopalia are connected via the rhopalial stalks and examination of the structure of the rhopalial stalks therefore becomes important when trying to comprehend visual processing. In the present study, the rhopalial stalk of the cubomedusae Tripedalia cystophora has been examined by light microscopy, transmission electron microscopy, and electrophysiology. A major part of the ring nerve is shown to continue into the stalk and to contact the rhopalial neuropil directly. Ultrastructural analysis of synapse distribution in the rhopalial stalk has failed to show any clustering, which indicates that integration of the visual input is probably spread throughout the CNS. Together, the results indicate that cubomedusae have one coherent CNS including the rhopalia. Additionally, a novel gastrodermal nerve has been found in the stalk; this nerve is not involved in visual processing but is likely to be mechanosensory and part of a proprioceptory system.This work was supported by grants 621-2002-4873 from the Swedish Research Council to D.-E. Nilsson and 21-2204-04 from the Danish Research Council to A. Garm.     

A Caulobacter gene involved in polar morphogenesis.

At specific times in the cell cycle, the bacterium Caulobacter crescentus assembles two major polar organelles, the flagellum and the stalk. Previous studies have shown that flbT mutants overproduce flagellins and are unable to form chemotaxis swarm rings. In this paper, we report alterations in both the stalk and the flagellar structure that result from a mutation in the flagellar gene flbT. Mutant strains produce some stalks that have a flagellum, produce some stalks that have an extra lobe protruding from their sides, have filaments lacking the 29-kilodalton flagellin, and produce several unusual cell types, including filamentous cells as well as predivisional cells with two stalks and predivisional cells with no stalk at all. We propose that flagellated stalks arise as a consequence of a failure to eject the flagellum at the correct time in the cell cycle and that the extra stalk lobe is due to a second site for the initiation of stalk biogenesis. Thus, a step in the pathway that establishes the characteristic asymmetry of the C. crescentus cell appears to be disrupted in flbT mutants. We have also identified a new structural feature at the flagellated pole and the tip of the stalk: the 10-nm polar particle. The polar particles appear as a cluster of approximately 1 to 10 stain-excluding rings, visible in electron micrographs of negatively stained wild-type cells. This structure is absent at the flagellar pole but not in the stalks of flbT mutant predivisional cells.     

DEVELOPMENT OF MUCILAGINOUS SURFACES IN EUGLENOIDS. I. STALK MORPHOLOGY OF COLACIUM MUCRONATUM1

The envelope and stalk of Colacium mucronatum Bourr. & Chad, were examined in living cells with light microscopy and in fixed preparations with scanning electron microscopy using critically point dried (CPD) and freeze dried (FD) preparations. The envelope of palmelloid cells is formed over the entire cell surface by many individual strands attached at right angles to areas of articulation of the pellicular strips. Strands were observed to anastomose on the posterior tip of otherwise naked cells. Stalks of living cells in India ink preparations had an optically dark inner core with a lighter outer sheath. In FD stalks a definite inner core was not evident, whereas CPD stalks had an outer surface composed of thick strands which may be the collapsed and aggregated strands of the FD stalks. In both there was also an amorphous matrix. The stalk forms from the aggregation of many strands from the anterior cell tip back to a point encompassing the cell surface anterior to a cross section of the tip 9 μm diam. The outer surface of the stalk comes from the pellicular surface joining that area and the core from the cell tip in the area of the canal opening. Any possible participation of the inner canal surface in stalk formation could not be determined because of the great density of the mucilage at the cell-tip/stalk junction.     

THE DEVELOPMENT OF CELLULAR STALKS IN BACTERIA

Extensive stalk elongation in Caulobacter and Asticcacaulis can be obtained in a defined medium by limiting the concentration of phosphate. Caulobacter cells which were initiating stalk formation were labeled with tritiated glucose. After removal of exogenous tritiated material, the cells were subjected to phosphate limitation while stalk elongation occurred. The location of tritiated material in the elongated stalks as detected by radioautographic techniques allowed identification of the site of stalk development. The labeling pattern obtained was consistent with the hypothesis that the materials of the stalk are synthesized at the juncture of the stalk with the cell. Complementary labeling experiments with Caulobacter and Asticcacaulis confirmed this result. In spheroplasts of C. crescentus prepared by treatment with lysozyme, the stalks lost their normal rigid outline after several minutes of exposure to the enzyme, indicating that the rigid layer of the cell wall attacked by lysozyme is present in the stalk. In spheroplasts of growing cells induced with penicillin, the stalks did not appear to be affected, indicating that the stalk wall is a relatively inert, nongrowing structure. The morphogenetic implications of these findings are discussed.     

中华绒螯蟹正常附着胚胎与流产胚胎的结构特点

用扫描电镜技术观察了中华绒螯蟹正常附着胚胎及流产胚胎的结构特点。结果表明,受精卵从生殖孔排出15min后,孵化室中的孵化液体积增大,使胚胎浸没在孵化液中,胚胎表面具有粘性;产卵后30min．卵柄初步形成;80～140min后卵柄完全形成,胚胎牢固地粘附在携卵绒毛上。正常胚胎的卵柄高度扭曲,上有很多毛状物,同时携卵刚毛上有很多粘液;流产胚胎的卵柄上无毛状物,但卵柄及胚胎表面有许多寄生物附着。携卵刚毛上的粘液及卵柄上的毛状物可能和胚胎附着有关;而胚胎表面寄生物的活动,可能使胚胎外被、卵柄以及卵索的结构发生变化,增加了胚胎之间的摩擦,进而胚胎呼吸困难,以致死亡和流产。     

Anatomical analysis of Saccharomyces cerevisiae stalk-like structures reveals spatial organization and cell specialization

Recently we reported an unusual multicellular organization in yeast that we termed stalk-like structures. These structures are tall (0.5 to 3 cm long) and narrow (1 to 3 mm in diameter). They are formed in response to UV radiation of cultures spread on high agar concentrations. Here we present an anatomical analysis of the stalks. Microscopic inspection of cross sections taken from stalks revealed that stalks are composed of an inner core in which cells are dense and vital and a layer of cells (four to six rows) that surrounds the core. This outer layer is physically separated from the core and contains many dead cells. The outer layer may form a protective shell for the core cells. Through electron microscopy analysis we observed three types of cells within the stalk population: (i) cells containing many unusual vesicles, which might be undergoing some kind of cell death; (ii) cells containing spores (usually one or two spores only); and (iii) familiar rounded cells. We suggest that stalk cells are not only spatially organized but may undergo processes that induce a certain degree of cell specialization. We also show that high agar concentration alone, although not sufficient to induce stalk formation, induces dramatic changes in a colony's morphology. Most striking among the agar effects is the induction of growth into the agar, forming peg-like structures. Colonies grown on 4% agar or higher are reminiscent of stalks in some aspects. The agar concentration effects are mediated in part by the Ras pathway and are related to the invasive-growth phenomenon.     

Manipulations in the peripheral stalk of the Saccharomyces cerevisiae F1F0-ATP synthase

The Saccharomyces cerevisiae F(1)F(0)-ATP synthase peripheral stalk is composed of the OSCP, h, d, and b subunits. The b subunit has two membrane-spanning domains and a large hydrophilic domain that extends along one side of the enzyme to the top of F(1). In contrast, the Escherichia coli peripheral stalk has two identical b subunits, and subunits with substantially altered lengths can be incorporated into a functional F(1)F(0)-ATP synthase. The differences in subunit structure between the eukaryotic and prokaryotic peripheral stalks raised a question about whether the two stalks have similar physical and functional properties. In the present work, the length of the S. cerevisiae b subunit has been manipulated to determine whether the F(1)F(0)-ATP synthase exhibited the same tolerances as in the bacterial enzyme. Plasmid shuffling was used for ectopic expression of altered b subunits in a strain carrying a chromosomal disruption of the ATP4 gene. Wild type growth phenotypes were observed for insertions of up to 11 and a deletion of four amino acids on a nonfermentable carbon source. In mitochondria-enriched fractions, abundant ATP hydrolysis activity was seen for the insertion mutants. ATPase activity was largely oligomycin-insensitive in these mitochondrial fractions. In addition, very poor complementation was seen in a mutant with an insertion of 14 amino acids. Lengthier deletions yielded a defective enzyme. The results suggest that although the eukaryotic peripheral stalk is near its minimum length, the b subunit can be extended a considerable distance.     

Co‐ordinate synthesis and protein localization in a bacterial organelle by the action of a penicillin‐binding‐protein

Organelles with specialized form and function occur in diverse bacteria. Within the Alphaproteobacteria, several species extrude thin cellular appendages known as stalks, which function in nutrient uptake, buoyancy and reproduction. Consistent with their specialization, stalks maintain a unique molecular composition compared with the cell body, but how this is achieved remains to be fully elucidated. Here we dissect the mechanism of localization of StpX, a stalk‐specific protein in Caulobacter crescentus. Using a forward genetics approach, we identify a penicillin‐binding‐protein, PbpC, which is required for the localization of StpX in the stalk. We show that PbpC acts at the stalked cell pole to anchor StpX to rigid components of the outer membrane of the elongating stalk, concurrent with stalk synthesis. Stalk‐localized StpX in turn functions in cellular responses to copper and zinc, suggesting that the stalk may contribute to metal homeostasis in Caulobacter. Together, these results identify a novel role for a penicillin‐binding‐protein in compartmentalizing a bacterial organelle it itself helps create, raising the possibility that cell wall‐synthetic enzymes may broadly serve not only to synthesize the diverse shapes of bacteria, but also to functionalize them at the molecular level.     

The behavior and the morphology of sea lilies with shortened stalks: implications on the evolution of feather stars

Extant crinoids can be divided into two groups, stalked sea lilies and stalkless feather stars. Feather stars are considered to have evolved from stalked ancestors by losing most of the stalk, but other differences are present between the two groups. The unsegmented centrodorsal, long and curved cirri near the crown, small calyx, and the ability to swim are all feather star features not found in the sea lilies. To figure out which of the above features evolved directly correlating with loss of the stalk in feather stars, we cut off the stalk from the sea lily Metacrinus rotundus and kept them alive in an aquarium. The specimens with shortened stalks were able to stand and crawl with their arms without the support of their stalks, but swimming was not observed for any of the animals. Morphologically, neither fusion of the remaining segments nor the reduction of the size of the calyx were observed, but the cirri became long and curved near the crown. Therefore, the extant sea lilies possess a potential to adapt to incidents of stalk loss. Specimens autotomizing most of their stalks were observed, suggesting that the potential is actually employed in nature. This mechanism linking the reduction of the stalk and the changes in the morphology of cirri may have played an important role in the evolution of the feather stars, if the stalked ancestors of feather stars also possessed this potential. Experimental zoological approaches as this study may provide new insights to the questions of evolution.     

Systemic infection of stalks and ears of corn hybrids by <Emphasis Type="Italic">Aspergillus parasiticus</Emphasis>

This study was conducted to explore systemic infection by the Aspergillus flavus group into corn ears via the stalk. An A. parasiticus mutant which produces norsolorinic (NOR) acid (a visible orange intermediate of the aflatoxin biosynthetic pathway) was used in field studies to monitor systemic infection of corn stalk and ear tissues. Corn hybrids resistant and susceptible to aflatoxin contamination were grown in the field and inoculated prior to tasseling by inserting A. parasiticus infested toothpicks into stalks between the 5th and 6th node below the lowest ear shoot. Beginning 2 weeks after inoculation, systemic infection by the NOR mutant was assessed weekly by collecting ear shank tissue and stalk tissue from the nodes between the infection sites and the developing ears. Ears were collected at the end of the growing season to determine the level of kernel infection by the NOR mutant. In two separate studies, the A. parasiticus NOR mutant was isolated from stalk tissues at all of node positions and ear shank tissue from several susceptible corn hybrid plants at the first harvest date 2 weeks after inoculation. The NOR mutant was also isolated from stalk and ear tissue of a resistant hybrid. The NOR mutant was only isolated from kernels of susceptible hybrids in 2003 and 2004. Infection rates of kernels in infected ears were very low (<1%). In 2005, the fungus was found in only one kernel from an ear of the resistant hybrid. The NOR mutant was not isolated from stalks, ears, or kernels from control (uninoculated) plants grown in the plots with inoculated plants. Although infection levels of corn kernels were low, systemic movement of the A. parasiticus up the stalk appears to be another possible route to infection of developing corn ears.     

Permian ginkgophyte fossils from the Dolomites resemble extant <Emphasis Type="Italic">O-ha-tsuki</Emphasis> aberrant leaf-like fructifications of <Emphasis Type="Italic">Ginkgo biloba</Emphasis> L

Background  

Structural elucidation and analysis of fructifications of plants is fundamental for understanding their evolution. In case of Ginkgo biloba, attention was drawn by Fujii in 1896 to aberrant fructifications of Ginkgo biloba whose seeds are attached to leaves, called O-ha-tsuki in Japan. This well-known phenomenon was now interpreted by Fujii as being homologous to ancestral sporophylls. The common fructification of Ginkgo biloba consists of 1-2 (rarely more) ovules on a dichotomously divided stalk, the ovules on top of short stalklets, with collars supporting the ovules. There is essentially no disagreement that either the whole stalk with its stalklets, collars and ovules is homologous to a sporophyll, or, alternatively, just one stalklet, collar and ovule each correspond to a sporophyll. For the transition of an ancestral sporophyll resembling extant O-ha-tsuki aberrant leaves into the common fructification with stalklet/collar/ovule, evolutionary reduction of the leaf lamina of such ancestral sporophylls has to be assumed. Furthermore, such ancestral sporophylls would be expected in the fossil record of ginkgophytes.     

Honey bee orientation behaviour and the influence of flower distribution on foraging movements

ABSTRACT.

• 1 Directional movement by foraging honey bees (Apis mellifera L.) was studied on several flower arrays. The most frequent move among equidistant flower stalks was straight ahead from stalk to stalk with frequencies decreasing for increasing turn angles. Turns to the left were about equal in frequency to turns to the right.
• 2 Bees maintained directionality when moving from flower stalks that had been rotated 90° counterclockwise while the bee was on the stalk (no difference between moves from rotated stalks and unrotated controls). Thus, directionality is maintained by the bee and is not an artefact of flower distribution.
• 3 Bees also maintained directionality when the entire array was rotated around the flower stalk the bee was on. Thus, bees use an external cue to orientate in a given direction rather than fixing on an inflorescence within the flower array.
• 4 Bees foraging on very different flower arrays differed in patterns of directionality and in distances flown between flower stalks. Therefore, even though bees maintain directionality using external cues, flower distribution can nevertheless influence flight patterns.

     

Effect of Mowing Cotton Stalks and Preventing Plant Re-Growth on Post-Harvest Reproduction of Meloidogyne incognita

The southern root-knot nematode (Meloidogyne incognita) is a major parasite of cotton in the U.S., and management tactics for this nematode attempt to minimize population levels. We compared three post-harvest practices for their ability to reduce nematode population levels in the field, thereby reducing initial nematode population for the next year's crop. The three practices tested were: 1) chemical defoliation before harvest plus cutting cotton stalks after harvest, 2) chemical defoliation plus applying a herbicide to kill plants prior to cutting the stalks, and 3) chemical defoliation without cutting stalks. Experiments were conducted in both the greenhouse and in the field. The greenhouse experiments demonstrated that M. incognita reproduction (measured as egg counts and root gall rating indices) was significantly greater when stalks were not cut. Cutting stalks plus applying herbicide to kill cotton roots did not significantly reduce nematode reproduction compared to cutting stalks alone. In field experiments, cutting stalks reduced egg populations and root galling compared to defoliation without stalk cutting. In a greenhouse bioassay which used soil from the field plots, plants grown in soil from the defoliation only treatment had greater root gall ratings and egg counts than in the stalk cutting plus herbicide treatment. Therefore, we conclude that cutting cotton stalks immediately after harvest effectively reduces M. incognita reproduction, and may lead to a lower initial population density of this nematode in the following year.     

THE MORPHOLOGY AND DEVELOPMENT OF SOME PROMINENTLY STALKED SOUTHERN AUSTRALIAN HALYMENIACEAE (CRYPTONEMIALES,RHODOPHYTA). I. CRYPTONEMIA KALLYMENIOIDES (HARVEY) KRAFT COMB. NOV. AND C. UNDULATA SONDER1

Several southern Australian red algae of the family Halymeniaceae (Cryptonemiales) are differentiated into hard, massive stalks and considerably softer laminar blades or phyllodes. The taxonomy, morphology and pit-connection ultrastructure of one such species, Cryptonemia kallymenioides (Harvey) Kraft comb. nov., are compared to C. undulata Sonder, which lacks massive stalks. In both species there is extensive periodic secondary cortication of the stalks, resulting in the formation of distinct “growth rings.” The blades of C. kallymenioides appear to be seasonal and its stalks perennial, while plants of C. undulata are apparently perennial but shorter lived than C. kallymenioides. As a result, stalks in the latter can reach 2–3 cm in diameter with up to 18 growth rings, compared to the 1–2 mm diameters and up to 6 rings within the stalks of C. undulata. Heavy secondary thickening of cortical cell walls occurs in both species and confers a “woody” texture to the stalks of C. kallymeniodes. Regardless of the large differences in average stalk diameters between the two species, the pit-connection ultrastructure from cortex to medulla shows much the same sequence of morphological modification. Pit-connections are standard red algal structures in the outer cortex, but become increasingly convoluted on the membrane-bound surfaces abutting cytoplasm and develop wider apertures and less dense cores with increasing distance from the stalk surface. In occasional medullary cells of C. kallymenioides, the cytoplasm disintegrates, leaving cell walls and pit-connections to play an apparently structural role which has not been reported in other red algae. It is suggested that the increase in aperture size and surface areas of pit-connections is compatible with their playing a role in the intercellular transport of solutes towards the inner cell layers which may, in C. kallymenioides, lie many millimeters distant.     

Carbon adsorption onto Fe oxyhydroxide stalks produced by a lithotrophic iron‐oxidizing bacteria

Iron (Fe)‐oxidizing bacteria have the potential to produce morphologically unique structures that may be used as biosignatures in geological deposits. One particular example is Mariprofundus ferrooxydans, which produces extracellular twisted ribbon‐like stalks consisting of ferrihydrite, co‐located with organic and inorganic elements. It is currently thought that M. ferrooxydans excrete and co‐precipitate polysaccharides and Fe simultaneously; however, the cellular production of these polysaccharides has yet to be confirmed. Here, we report on a time‐series study that used scanning transmission X‐ray microscopy and C 1s and Ca 2p near‐edge X‐ray adsorption fine structure spectroscopy to investigate production of polysaccharides over the growth cycle of M. ferrooxydans. The production and morphology of twisted iron stalks were consistent with previous observations, but unexpectedly, in the log phase, the carbon content of the stalks was extremely low. It was not until stationary growth phase that a significant component of carbon was detected on the stalks. During the log phase, low levels of carbon, only detectable when the stalks were thin, suggested that M. ferrooxydans produce an extracellular polysaccharide template onto which the Fe precipitates. By stationary phase, the increased carbon association with the stalks was a result of adsorption of organic compounds that were released during osmotic shock post‐stalk production. In the environment, elevated concentrations of DOC could adsorb onto the Fe stalks as well as a number of other elements, for example, Si, P, Ca, which, by preventing chemical interactions between the Fe nanoparticles, will prevent structural deformation during recrystallization and preserve the structure of these filaments in the rock record.     

Multicellular Stalk-Like Structures in Saccharomyces cerevisiae

Stalk formation is a novel pattern of multicellular organization. Yeast cells which survive UV irradiation form colonies that grow vertically to form very long (0.5 to 3.0 cm) and thin (0.5 to 4 mm in diameter) multicellular structures. We describe the conditions required to obtain these stalk-like structures reproducibly in large numbers. Yeast mutants, mutated for control of cell polarity, developmental processes, UV response, and signal transduction cascades were tested and found capable of forming stalk-like structures. We suggest a model that explains the mechanism of stalk formation by mechanical environmental forces. We show that other microorganisms (Candida albicans, Schizosaccharomyces pombe, and Escherichia coli) also form stalks, suggesting that the ability to produce stalks may be a general property of microorganisms. Diploid yeast stalks sporulate at an elevated frequency, raising the possibility that the physiological role of stalks might be disseminating spores.     

Developmental plasticity and regenerative capacity in the renal ureteric bud/collecting duct system

Branching morphogenesis of epithelia is an important mechanism in animal development, being responsible for the characteristic architectures of glandular organs such as kidney, lung, prostate and salivary gland. In these systems, new branches usually arise at the tips of existing branches. Recent studies, particularly in kidney, have shown that tip cells express a set of genes distinct from those in the stalks. Tip cells also undergo most cell proliferation, daughter cells either remaining in the tip or being left behind as the tips advance, to differentiate and contribute to new stalk. Published time-lapse observations have suggested, though, that new branches may be able to arise from stalks. This happens so rarely, however, that it is not clear whether this reflects true plasticity and reversal of differentiation, or whether it is just an occasional instance of groups of tip cells being "left behind" by error in a mainly stalk zone. To determine whether cells that have differentiated into stalks really do retain the ability to make new tips, we have removed existing tips from stalks, verified that the stalks are free of tip cells, and assessed the ability of tip-free stalks to initiate new branches. We find stalks to be fully capable of regenerating tips that express typical tip markers, with these tips going on to form epithelial trees, at high frequency. The transition from tip to stalk is therefore reversible, at least for early stages of development. This observation has major implications for models of pattern formation in branching trees, and may also be important for tissue engineering and regenerative medicine.     

Soluble and insoluble invertase activity in elongating Tulipa gesneriana flower stalks

Previously 'frozen' Tulipa gesneriana L. bulbs cv. Apeldoorn, were planted and grown at higher temperatures to study the role of invertase (EC 3.2.1.26) in the cold-induced elongation of the flower stalk internodes. After planting, flower stalks were left intact, or, the leaves and flower bud were both removed to inhibit internode elongation. In intact flower stalks, elongation of the internodes was accompanied by an accumulation of glucose and an initial decrease in the sucrose content g,⁻¹ dry weight. Insoluble invertase activity g,⁻¹ dry weight hardly changed, but soluble invertase activity showed a peak pattern, that was related, at least for the greater part, to the changes in the sugar contents. Peak activities of soluble invertase were found during (lower- and uppermost internodes) or around the onset of the rapid phase of internode elongation (middle internodes). Internode elongation and glucose accumulation immediately ceased when the leaves and flower bud were removed. Insoluble invertase activity g,⁻¹ dry weight remained at its initial level (lowermost internode) or increased more towards the upper internodes. Soluble invertase activity did not further increase (uppermost internode) or decreased abruptly to a low level. It is concluded that soluble invertase may be one of the factors contributing to glucose accumulation and internode elongation in the tulip flower stalk.     

Asphodelus aestivus,an example of synchronization with the climate periodicity

The phenology ofAsphodelus aestivus Brot. is described by means of a phenological model which has been formulated to fit skewed phenological data. Based on the model parameters the timing of different phenophases of biomass accumulation were determined. The biomass oscillations of leaves, inflorescence stalks and tubers were found to be synchronized with the predictable seasonal climatic changes. In addition, the plant seems to respond to minor random climatic variations. The emergence of leaves and inflorescence stalks depends on stored material in the tubers while leaf and inflorescence stalk elongation as well as flowering depends on current production. The storage part of the tubers seems to be a regulating structure, which is responsible for the synchronization ofA. aestivus productivity with the seasonality of the Mediterranean climate.A. aestivus is considered to be a Competitor Ruderal and Stress tolerant (C-R-S) strategist which may explain the wide distribution of this plant over the Mediterranean Basin.