Changes In Growth Form Research Articles

Basal rosette or floating leaf canopy – an example of plasticity in a rare aquatic macrophyte

The rare aquatic macrophyte Luronium natans can be encountered with two growth forms: as a bottom-dwelling plant with a rosette of linear leaves, or as a nymphaeid plant with long-petioled oval floating leaves. The change of growth form corresponds to a change in size class (small and submerged vs. tall and canopy-forming).

Estructura de un ecotono bosque Subalpino-pastos alpinos (Las Cutas, Ordesa, Pirineos Centrales)

We describe the structure of a subalpine forest-alpine pasture ecotone in the Central Pyrenees, that includes altitudinal timberline and treeline, and it is dominated by Pinus uncinata Ram . We measured for each P. uncinata 21individual located inside a rectangular plot parallel to the slope: the location and several structural and groivth form variables (number and type of stems per individual). Then, P. uncinata individuals were classified according to their size (adults, poles, saplings and seedlings) and growth form (krummholz —shrubby and multistemmed individuals—, krummholz with vertical stems). The ecotone structure was described through the study of groivth form and size changes of P. uncinata individuals across the ecotone and related to the area climate, that is characterized by maximum snow thickness in spring (April) and strong N-NW-W winds. Most of living individuals were krummholz, located above the timberline in the area where seedlings were abundant. Bigger, vertical and unistemmed individuals predominated in the forest. The structure or growth form changes were sharp across the ecotone. Crown injuries due to wind effects were evident in shrubby individuals and predominated in those directions that showed stronger winds during the year. The snow-wind interaction can explain partially the location of the studied timberline that could be considered a local phenomenon. The spatial location of the different classes of individuals, the spatial interaction between seedlings and krummholz individuals, and the changes of growth form (from arborescent to shrubby or vice versa) can modify the response of these P. uncinata populations to climate changes.

Variability of stable isotopes and maximum linear extension in reef-coral skeletons at Kaneohe Bay, Hawaii

Stable-isotope and growth records of coral skeletons are often used to reconstruct tropical paleoclimate, yet few surveys have systematically examined the natural variability in coral skeletal 13C, 18O and maximum linear skeletal extension (MLSE) across depth. Here, interspecific, intraspecific, and geographical variations in coral skeletal 13C, 18O, and MLSE were examined in the corals Porites compressa, P. lobata, and Montipora verrucosa grown at 1.7, 5.0, and 8.3 m depth from August 1996 to March 1997 at The Point Reef and Patch Reef #41 field sites in Kaneohe Bay, Hawaii. Coral skeletal 13C values significantly decreased with depth and differed between species, but did not vary between field sites. 18O values were not significantly different across depth within a species, but did differ among species and field sites. High-resolution analysis of the intra-annual variation in skeletal 13C and 18O in P. compressa at 2.0 m depth confirms that these isotopes reflect changes in solar irradiance and temperature, respectively. Changes in MLSE across depth were consistent within, but highly variable among, species. Peak MLSE occurred at 1.7, 5.0, and 8.3 m for P. lobata, P. compressa, and M. verrucosa, respectively. Such interspecific variation in MLSE patterns may be attributable to one or more of the following: increases in zooplankton in the diet, changes in metabolic processes, or changes in growth form with depth. Overall, these results imply that natural inter- and intraspecific variability in coral skeletal 13C, 18O, and MLSE should be considered when interpreting and comparing coral-based tropical paleoclimate data from various coral species, depths, and field sites.

PHYLOGENETIC ANALYSIS OF TRAIT EVOLUTION AND SPECIES DIVERSITY VARIATION AMONG ANGIOSPERM FAMILIES.

Angiosperm families differ greatly from one another in species richness (S). Previous studies have attributed significant components of this variation to the influence of pollination mode (biotic/abiotic) and growth form (herbaceous/woody) on speciation rate, but these results suffer difficulties of interpretation because all the studies ignored the phylogenetic relationships among families. We use a molecular phylogeny of the angiosperm families to reanalyse correlations between S and family-level traits and use reconstructions of trait evolution to interpret the results. We confirm that pollination mode and growth form are correlated with S and show that the majority of changes in pollination mode involved a change from biotic to abiotic pollination with an associated fall in speciation rate. The majority of growth form changes involved the evolution of herbaceousness from woodiness with a correlated rise in speciation rate. We test the hypothesis of Ricklefs and Renner (1994) that "evolutionary flexibility" rather than other trait changes triggered increased speciation rates in some families, but find little support for the hypothesis.

Effects of drought and flooding on the reproduction of an amphibious plant, Ranunculus peltatus

Aquatic seedlings of Ranunculus peltatus Schrank were subjected to three levels of drought (dry, saturated and flooded) at two different phenological stages, vegetative stage and at onset of flowering. Changes in growth form, timing of flowering, number of flowers and fruits and the number of seeds per fruit were monitored to test the effect of drought on reproduction. Plants that were transferred to a terrestrial, but water-saturated, environment at a vegetative stage rapidly changed from an aquatic, spreading, elongated growth form to a prostrate growth form and produced only slightly fewer seeds per pot (86) than the flooded control plants (93). Total seed production was decreased by 1000 seeds per pot in both saturated treatments compared to the control treatment. There was no significant difference in total seed production between plants encountering drought at a vegetative or a flowering stage (2471 vs. 2348 seeds per pot). Plants subjected to air drying of the soil (no water added) at both phenological stages changed growth form, but flower, fruit and seed production was negligible. The fact that total seed production was still relatively high under water-saturated conditions at both phenological stages may explains partially why this species is successful in temporary marshes where drought often occurs during its lifecycle.

Spruce‐fir growth form changes in the forest‐tundra ecotone of Rocky Mountain National Park, Colorado, USA

Tree regeneration has traditionally been used as a measure of the response of treeline to climate Changes in growth form of krummholz trees may also indicate whether treeline is responding to changes in climate The purpose of this study was to determine whether krummholz trees m the forest‐tundra ecotone of Rocky Mountain National Park, Colorado have experienced significant vertical stem growth, in the absence of mortality, and if this growth occurred in response to recent changes in climate We sampled and dated Engelmann spruce and subalpine fir krummholz leaders stratified by height class at three sampling locations to determine the dates leaders initiated growth above mean snow depth At one sampling location, 215 additional leaders were sampled to construct an age structure of leader release dates Dates of leader release taken from the age structure were compared with seasonal temperatures, seasonal precipitation, winter snow depths, and annual runoff using t‐tests Dates of leader release were also compared to proxy climate records for the southern Rocky Mountain region Based on historical photos as well as the data presented here, both spruce and fir krummholz trees experienced significant height growth as early as the 1850's and continued to grow vertically, at least through the 1970's This vertical stem growth occurred in the absence of significant mortality Running mean annual temperature and May snow depth are both positively associated with years of leader release, suggesting that a warmer, wetter climate, possibly following the end of the Little Ice Age ca 1850, may have induced these changes in the ecotone

Mycorrhizas—Integrated development between roots and fungi

Most vascular plants have coevolved with root inhabiting symbiotic fungi and the resulting structures, mycorrhizas, are the result of the close association and a subsequent modification of both symbionts. In vesicular-arbuscular mycorrhizas, the mycobiont undergoes pronounced alterations in morphogenesis involving appressorium formation, arbuscule development and, in some genera, differentiation of vesicles. The triggers for these modifications are unknown. Changes in the roots primarily involve subcellular modifications. In ectomycorrhizas, hyphae of the mycobiont undergo dramatic changes in growth form as they contact the root surface and as they penetrate intercellularly. The underlying mechanism controlling the change in hyphal branching may involve the cytoskeleton, but to date there is little evidence for this. Ericoid mycorrhizas are specialized on the hair roots of members of some families in the Ericales. Considerable information has been obtained on the role of the mucilaginous sheath surrounding those roots in the colonization process. Appressorium formation precedes hyphal penetration of epidemal cells and subsequent coil formation. In orchids little is known about the initial contact between fungal hyphae and either protocorms or roots. In both structures, there is some evidence that entry may be via epidermal outgrowths (hairs). Hyphae develop intracellularly and are surrounded by host plasma membrane. Ectendo-mycorrhizas, arbutoid mycorrhizas and monotropoid mycorrhizas are of limited occurrence and have been studied less extensively.

Mycorrhizas: Integrated Development between Roots and Fungi

Most vascular plants have coevolved with root inhabiting symbiotic fungi and the resulting structures, mycorrhizas, are the result of the close association and a subsequent modification of both symbionts. In vesicular-arbuscular mycorrhizas, the mycobiont undergoes pronounced alterations in morphogenesis involving appressorium formation, arbuscule development and, in some genera, differentiation of vesicles. The triggers for these modifications are unknown. Changes in the roots primarily involve subcellular modifications. In ectomycorrhizas, hyphae of the mycobiont undergo dramatic changes in growth form as they contact the root surface and as they penetrate intercellularly. The underlying mechanism controlling the change in hyphal branching may involve the cytoskeleton, but to date there is little evidence for this. Ericoid mycorrhizas are specialized on the hair roots of members of some families in the Ericales. Considerable information has been obtained on the role of the mucilaginous sheath surrounding those roots in the colonization process. Appressorium formation precedes hyphal penetration of epidemal cells and subsequent coil formation. In orchids little is known about the initial contact between fungal hyphae and either protocorms or roots. In both structures, there is some evidence that entry may be via epidermal outgrowths (hairs). Hyphae develop intracellularly and are surrounded by host plasma membrane. Ectendo-mycorrhizas, arbutoid mycorrhizas and monotropoid mycorrhizas are of limited occurrence and have been studied less extensively.

Chaetetid skeletons as short-term records of physical disturbance events

The growth records of spongiomorph and colonial skeletons have great potential for revealing the short-term depositional dynamics of ancient shallow marine environments. The utility of such skeletons for understanding the type and frequency of physical disturbance is illustrated by chaetetid-bearing limestones from Pennsylvanian (Desmoinesian) cyclothems of southeastern Kansas. Individual chaetetids frequently contain growth-interruption surfaces that are marked by clay partings or encrusting overgrowths of epibionts. Such interruptions occur irrespective of the growth form of the chaetetids, although they are more conspicuous in laminar and domical growth forms with ragged margins. Growth forms with smooth margins and fewer interruptions are more commonly high domical to columnar. The latter occur in cleaner carbonates with higher rates of carbonate accumulation and little siliciclastic influx.Interruption surfaces, which may be accompanied by reorientation of skeletal growth, record significant depositional and erosive events during the life history of the chaetetids. Similar surfaces have been described from a variety of other organisms including stromotoporoids, fistuliporoid and trepostome bryozoans, and favositid corals. In most environments, physical disturbance events of this time scale are invariably destroyed by subsequent bioturbation or current reworking. For this reason, chaetetid skeletons provide a valuable means of inferring the frequency and intensity of physical distubance and the rate of sediment accumulation.The temporal significance of growth interruptions must be determined before their environmental significance can be assessed. Geometry of calicle growth at these surfaces is critical for recognizing the manner in which growth was reestablished. Colonization by the settling of larvae on a dead surface has a much different implication than rejuvenation from surviving calicles. The former could occur on long dead skeletal hardgrounds, and the latter indicates physical disruptions during the life of a single chaetetid. Clay partings and clay-filled calicles record mud burial events resulting in partial mortality, followed by rapid rejuvenation and overgrowth of the sediment. Encrustation of growth-interruption surfaces by auloporid corals, and more rarely bryozoans and stromatolitic algae, indicate prolonged exposure of the skeletal surface and subsequent recolonization. Interestingly, auloporid encrustation appears to be more common in clay-rich carbonates having evidence of more frequent and higher-energy disturbance events. Evidence of dissolution or biocorrosion of the skeletal surface may imply an even longer period of exposure between disturbance and recolonization.Local development of chaetetid mounds and biostromes also permits larger-scale environmental fluctuations to be recognized. Changes in growth form, typically associated with changes in clay content of the enclosing carbonates, appear to reflect fluctuations in clastic sediment influx and water turbidity. Subtle clay-rich intervals and unconformity surfaces are recognized within chaetetid-bearing units only a few meters thick. The thin sedimentation units thus defined appear to be correlative between outcrops separated by tens of kilometers.Close examination of spongiomorph and colonial skeletons therefore has the potential to shed light on depositional processes and environmental changes at time scales of tens to thousands of years normally inaccessible to paleoecologists.

Observations on growth form and habit of potassium nitrate as a function of the temperature

Crystals of potassium nitrate were grown in a flow system in order to find out whether fluctuations in growth rate of the faces with the temperature as observed by Sipyagin and Chernov [Soviet Phys.-Cryst. 17 (1973) 881] and Chernov et al. (in: Growth of Crystals, Vol. 12 (Consultants Bureau, New York, 1984) p. 103] lead to expected drastic changes in growth form and habit. Slight changes in both growth form and habit have been observed but they were different from the changes we expected. Discrepancies with the data of Sipyagin et al. are explained by differences in experimental circumstances.

Plant size, nutrient composition and biomass productivity of oats and faba bean in intercropping, and the effect of controlling Rhopalosiphum padi (Hom., Aphididae) on these properties

Effects of mixed intercropping on plant size, content of mineral nutrients and biomass yields were examined in three field experiments in Southern Finland in 1983—1985. The stand types were monocrops and replacement series of mixtures with 2/3 and 1/3 or 1/3 and 2/3 of oats (Avena sativa) and faba bean (Vicia faba), respectively. In one of the experiments control of R. padi, by means of deltamethrin sprayings, was an additional experimental factor having two levels. The height of stems or the above ground biomass of oats either were not affected or were increased by crop diversification. Bean plants remained smaller in the mixtures than in the monocrop. In plant size, there was a significant interaction between stand type and the effect of aphicide spraying: Oat benefitted most from being grown in the mixture containing most bean, and there was an indication (not statistically significant) that in these mixtures bean had proportionately higher weight loss. This result was interpreted as giving some support to the hypothesis of interspecific compensation between oats and bean against aphid damage to oats. In oats, the content of N, P, K, Ca, and Mg all decreased from the stage of inflorescence emergence to the stage of the onset of milk development. Mixed cropping increased the content in oats of all these nutrients except Ca. At the same time, contents of P and K in bean were decreased. The changes in growth form and composition in oats induced by intercropping are discussed from the point of view of host plant relationship and damage function of the aphid pest. In terms of relative yield total (RYT), there was no overyielding in the dry matter, and in one case only was there overyielding in the nitrogen. During the period of population growth of R. padi, the daily maximum temperatures within the canopy were higher in the mixtures than in the monocrop of oats.

Predicted Evolutionary Response to Selection for Tolerance of Soybean (Glycine max) and Intraspecific Competition in a Nonweed Population of Poorjoe (Diodia teres)

Genetic variation within a nonweed (coastal) population of poorjoe was measured in an experimental population subjected to soybean and intraspecific competition for space and light. A sib analysis was used to estimate phenotypic and genetic variance/covariance components of aboveground biomass production and five independent measurements of growth defined by a path-coefficient model. A multivariate analysis of response to selection was applied to predict evolutionary change in the growth measurements in response to selection for performance under soybean and intraspecific space/light competition; sufficient genetic variation was present in the experimental population to allow a rapid response to this selection. Selection under competitive conditions was predicted to cause the nonweed population to emerge earlier, grow faster early in development, change in growth form, and grow faster under a soybean canopy. Most of these changes would increase the resemblance of the selected population to a weed population of poorjoe. However, the growth rate of the selected population under a soybean canopy was predicted to become greater than that actually observed in the present-day weed population. Multivariate analysis of response to selection may be generally useful in predicting evolutionary response of plant pest populations to control practices.

Dimorphismus im system der pilze — grauzone der taxonomie?

Dimorphic fungi can grow as mycelial phase and as yeast phase. The change of growth form is effected by an altered programme in gene expression, which is induced either in certain stages of ontogenesis or by environmental factors. Therefore it is necessary to distinguish ontogenetically conditioned (irreversible) and environment conditioned (reversible) dimorphism. The first is characteristic for dimorphic Ustomycetes, Basidiomycetes and related anamorphs as well as for Taphrinales; the second for the majority of dimorphic Ascomycetes, Endomycetes, and related anamorphs. The integration of dimorphic fungi in the systems of filamentous fungi and of yeasts--which originally have been elaborated rather independently--was difficult in many cases. In recent times, the study of certain ultrastructural and biochemical-physiological characters has much facilitated the taxonomic arrangement of dimorphic fungi and has allowed to demonstrate some phylogenetic relations among filamentous, dimorphic, and yeast fungi. The authors hold the concept that yeasts have evolved from filamentous resp. dimorphic fungi by neotenic simplification.

The Structure and Regulation of Some South American Kelp Communities

The main objective of this study was to evaluate how physical stress and herbivores influence the distribution, abundance, size frequency, and mortality of the giant kelp, Macrocystis pyrifera, in the southeast Pacific. These factors were studied for the kelp and the echinoid herbivore Loxechinus albus over a wide latitudinal range (56°—42° S) of South America on RV Hero cruises in 1972 and 1973. There were large kelp forests with many large plants in the southern Isla de los Estados and Tierra del Fuego sites. Sources of kelp mortality in these sites include entanglement with drift plants and heavy encrustation of bivalves. This resulted in a considerable amount of drifting kelp, and the sea urchins appeared to have abundant food and did not attack living kelp plants. Nevertheless, the urchin densities usually were relatively low and the Loxechinus size frequencies skewed to larger size classes, suggesting that their populations may be limited by larval availability in the Westwind Drift. There were also some large kelp forests in the northern Golfo Corcovado and Isla Chiloe areas, but here the kelp forests seemed relatively ephemeral and Loxechinus appeared to be harvested by humans. The intermediate latitudes (54°—46° S) in areas semiexposed to oceanic waves were characterized by situations in which Loxechinus overexploit the kelps and maintain urchin—coralline algae "barren grounds." In these areas kelps occur only where urchin access is restricted by wave exposure, ephemeral clumps of Desmarestia ligulata, and rarely, by a predator, the asteroid Meyenaster gelatinosus. In many areas the shallow distribution of Macrocystis was restricted by competition with the large fucoid Durvillaea antarctica. These relationships were evaluated by removal and addition experiments. Much more important than latitudinal relationships to both kelp and urchin distribution and abundance patterns were exposure gradients, from shores subject to strong oceanic swells to protected fjords. Transect data suggest that Loxechinus disappear from protected waters before Macrocystis. Thus in some semiprotected habitats there are very dense patches of kelps without grazers; kelp removal experiments in these habitats suggest strong density—dependent kelp interactions. In still more protected sites, the Macrocystis growth form changes, the plants appear to have low fertility, and there is very low recruitment. Summarizing, the Loxechinus population seems restricted by larval recruitment in the face of the Westwind Drift in the far south, perhaps by sedimentation or fresh water in protected fjords, and by human fishing in the north. The very low Loxechinus densities in the far south are correlated with large kelp forests in which the main kelp mortality results from drifting Macrocystis plants. The kelp populations appear limited by physical factors in the fjords and by Loxechinus grazing in most other areas.

Mature Phenotype in Hemerocallis Plantlets Fortuitously Generated In Vitro

Daylily plantlets generated on semi-solid media from morphogenetically competent cells or morphogenetically competent cells regenerated from protoplasts can give rise in aseptic culture to plantlets with a mature phenotype. The individual leaves of these plantlets open to the extreme base so that no encircling leaf sheath is present. This permits the overlapping bases and leaves to assume an open fan-like arrangement. The occurrence of fans correlates with exceptionally tightly sealed culture vessels and experiments to date suggest a gaseous component is associated with this change of growth form. It has not been possible to fix the mature growth mode, however, and new leaf growth assumes the more normal juvenile phenotype when the gaseous environment is altered by admitting or exposure to room air.

Stream-Grade Variation and Riparian-Forest Ecology Along Passage Creek, Virginia

U.S. Geological Survey, National Center, M.S. 461, Reston, VA 22092 Hupp, CLIFF R. (U.S. Geol. Surv., National Center, Mail Stop 461, Reston, Virginia 22092). Stream grade changes and riparian-forest ecology along Passage Creek, Virginia. Bull. Torrey Bot. Club 109: 488-499. 1982.-Passage Creek, in northwestern Virginia, flows on relatively nonresistant shales, then cuts through a gorge underlain by resistant sandstone. In the gorge, the stream gradient steepens, the size of bed material increases, a braided channel forms, and riparian-forest composition and growth form changes relative to areas outside the gorge. Effects of flooding are intensified within the gorge and revealed in the pattern and deformation of streamside vegetation. Increased stream gradient within the gorge provides for high stream power and coarse sediment deposition relative to the flood plain outside the gorge. A more diverse upland forest grows on the flood plain in the gorge. The riparian forest in the gorge may be an example of a nonequilibrium forest, resulting from periodic disturbance by destructive floods. Recognition of vegetation patterns resulting from such disturbances may be useful in detection of potential flooding.

Electrodeposition of copper on a copper single-crystal (100) face and on a copper polycrystalline surface in the presence of sulphaguanidine

In the presence of sulphaguanidine a triangular pyramid growth form changes successively to a layer type of growth which transforms to ridges and then to a polycrystalline deposit on a (100) single-crystal copper substrate. On a polycrystalline copper surface the grain size of the deposit is affected markedly by sulphaguanidine. The change in the growth form and overpotential are explained with the help of IR and X-ray techniques.

Watercress ( Nasturtium microphyllum (Boenn.) RCHB. and N. officinale in New Zealand cold springs

Watercress ( Nasturtium microphyllum and N. officinale) is shown to be common in New Zealand cold springs, growing both as an emergent and a submerged plant. At Waikoropupu Springs, a 2-year study recorded the seasonal changes in growth form and biomass of emergent N. microphyllum. Watercress was also found to grow submerged to a depth of 6.5 m with a growth form, in summer, different from that of the emergent plant and with a much lower biomass.

The Cytogeography of Impatiens L. (Balsaminaceae)

Many plant genera are known to include species with different basic chromosome numbers; such occurrences are generally of interest, but more particularly when cytological variation of this sort is correlated with changes in growth form, reproductive behaviour or distribution. Impatiens L. is a genus of this type-one in which both variation in basic number and the incidence of polyploidy show decided geographical patterns. Recent studies at the Jodrell Laboratory, Kew, make a significant contribution to this knowledge and form the basis for this first report. Impatiens is essentially a montane genus of the Old World containing over 500 species, half of which occur in the sub-continent of India. It is common in Burma and Africa but less so in SE. Asia and is relatively rare in northern Asia, Europe and North America. There is no taxonomic monograph of the genus and the only significant attempts at classification of the species are those of Hooker (1874-5) and again Hooker (1904-6). The classifications are markedly different in the two works due to the discovery of many more species in the intervening years. It had also become more apparent that endemism was prevalent and this resulted in a primarily phytogeographic treatment of the species in the later work. More recently it has been estimated that as many as 91 per cent. of the Indian species are endemics (Chatterjee, 1940: 44)Cytological studies have also been few in number and, prior to the present study, only twenty-three species had been chromosome counted. The latest and most substantial contributions have been made by Khoshoo (1955, 1956, 1957) who, in his I957 paper, lists and reviews all the previous works. At that time two main cytological characteristics of the genus emerged, namely that it was exclusively diploid and that the basic numbers of the species showed considerable variation (x = 6, 7, 8, Io). Although limited, the combined data also suggested that x = 8 might be typical for African species.

Some effects of soil physical condition on ryegrass growth

Summary Two experiments are reported, wherein soil physical condition was changed by (1) compaction treatments and (2) compaction and puddling treatments. Seedlings of perennial rye grass (Lolium perenne L.) and short-rotation ryegrass (L. perenne × L. multifiorum Lam.) were used in the winter 1955. Both rye grasses were tolerant of increasing soil compaction, the only effects being ephemeral changes in growth form, and differences in root distribution. Where the soil had been puddled, the growth of both ryegrasses was reduced, but a compaction three weeks after the puddling appeared to remove the worst effects of the puddling.