Compression wood in rooted cuttings of Douglas-fir

Rooted cuttings of three clones of Douglas-fir [ Pseudotsuga menziesii (Mirb.) Franco] were growing plagiotropically two seasons after propagation. The oblique growth habit of cuttings was due, in part, to dorsoconvex curvature of the wood of the original 12-cm cuttings after rooting. In cross sections taken 1.5–2.0 cm from the bases of cutting stems, the total widths of xylem and compression wood were significantly greater on the morphologically upper (convex) than on the lower sides of the stems. This was due to an asymmetry in the growth ring produced the season following rooting. In nearly every cross section examined, 80–90% of the width of the upper side of this growth ring was compression wood. Examination of cross sections taken 1.5–2.0 cm from the distal ends of the wood of original cuttings revealed a shift in the position of compression wood formation during the second season. As the distal portions of their stems were displaced from the vertical by curvature, cuttings of two clones produced compression wood on their lower sides in this region. Cuttings from the third clone, which showed the least basal curvature, continued forming compression wood on their upper sides in the distal portions of the original cuttings.     

Effect of seasonal changes in the photosynthates mannitol and laminaran on maturation of Ecklonia cava (Phaeophyceae, Laminariales) in Nishiki Bay, central Japan

Seasonal changes in the contents of two photosynthates, namely, mannitol and laminaran, were investigated in Ecklonia cava Kjellman with reference to its maturation. The samples were collected from a depth of 8 m in Nishiki Bay, central Japan. The mannitol and laminaran contents in the bladelets were measured. We also determined the content of these photosynthates in the bladelets occupying different positions on the frond and in the sorus and non‐sorus portions of the bladelets. The maturation of sori initiated in July and peaked in October. The content of the two photosynthates in the bladelets was low in winter; this coincided with the active formation of new bladelets. Mannitol levels were high during the beginning of the maturation season in summer. Laminaran, in particular, was present in the bladelets only in summer. The laminaran content was higher in the sorus portions than in the non‐sorus ones; however, the mannitol content was almost equal in both portions. The laminaran content was high only in the bladelets just prior to maturation and in the mature bladelets at the beginning of the maturation season. These results suggested that mannitol and laminaran were important energy sources for the maturation of E. cava from summer to autumn, and laminaran in particular was closely associated with the maturation of reproductive structures.     

Size and reproduction of Thelypteris limbosperma and Athyrium distentifolium along environmental gradients in Western Norway

The performance of the ferns Thelypteris limbospgrma and Athyrium distentifolium , as expressed by number of son on pinnules and frond size, has been related to environmental gradients. Data have been collected from homogenous fern-dominated stands from different geographical areas in Western Norway. Number of sori produced, which was assumed to indicate fern fertility, was highly variable. There were significant correlations between frond size and fertility, but only 35–46 % of the variation in fertility could be explained by differences in frond size. The highest number of sori was found on plants of medium size, and for A. distentifolium there was a statistically significant reduction in sori number on fronds taller than 125 cm. For the linear relationships between fertility and size, it is suggested that the small X-intercept and slope defines the high competitive ability of A. distentifolium in sites with a long-lasting snow cover. The ferns may dominate in large stands even though their fertility is low or zero, which indicates that they under certain ecological conditions mainly reproduce vegetatively. Both ferns show decreased fertility both toward their altitudinal and lowland distribution limits, but their fertility optima were different. The performances of the two fern species showed highly different responses to geographical and climatical variables. The fertility of T. limbosperma could be predicted by mean July- and January temperatures, humidity and canopy cover, while the fertility of A. distentifolium could not be predicted by any of the site environmental variables investigated.     

New Middle Jurassic record of fern genus Eboracia (Dicksoniaceae,Filicales) and its spatio-temporal distribution in China

As an important component of the Mesozoic flora, the extinct fern genus Eboracia Thomas (Dicksoniaceae, Filicales) is widely reported in China with diverse fossil records. New material of Eboracia lobifolia, represented by a nearly intactly preserved fossil frond, is described herein from the Middle Jurassic Haifanggou Formation in Beipiao of western Liaoning, Northeast China. The frond is lanceolate in gross outline, at least 38.0 cm long, and can be divided into the basal sterile part, the upper fertile part and a transitional part in between. The new discovery confirms for the first time that the frond of E. lobifolia is hemidimorphic rather than holodimorphic. Many in-situ spores were detached from the sori of the fertile pinnae, which are characterized by rounded-tetrahedral shape, smooth surface, distinct border, and a wide, long triradiate crack almost reaching the equator. Comparing with dispersed spores in the same horizon, these in-situ spores seem to be most similar to Cyathidites minor Couper in morphology. A spatio-temporal analysis of Eboracia in China shows that Eboracia with totally four species occurred in a time interval ranging from the Late Triassic to the Early Cretaceous in China, and mostly flourished in the Middle Jurassic; the genus was widely distributed in both the Northern and Southern Phytofloristic Provinces of China, particularly in southern China during the Late Triassic to Early Jurassic, while more abundant and diverse in northern China during the Middle Jurassic to Early Cretaceous.     

Sorus development on median and marginal parts of the sporophyte of Laminaria japonica Areschoug (Phaeophyceae)

Sorus formation on median and marginal parts of Laminaria japoncia Areschoug was investigated by cultivating sporophytes from December 1996 to September 1997 in Southern Hokkaido, Japan. Simultaneously, discs (ca. 3 cm in diameter) that were cut off monthly from median and marginal parts of the cultivated sporophytes were incubated in our laboratory. All the cultivated sporophytes formed sori on the median parts from January to August, while all the median and marginal discs formed sori at 10 under 46 μmol photon m^-2s^-1 (12L:12D) in enriched medium. There was no difference in sorus area between median and marginal discs. These results indicated that the marginal parts are able to produce sori, although the greater part of them are actually washed away before forming sori in the sea. The marginal part is probably in a state of `resource limitation' on the reproduction because the resource outflowed from this part to the basal part for the growth of sporophytes. This revised version was published online in August 2006 with corrections to the Cover Date.     

The origin of the sporophyte shoot in land plants: a bryological perspective

Background

Land plants (embryophytes) are monophyletic and encompass four major clades: liverworts, mosses, hornworts and polysporangiophytes. The liverworts are resolved as the earliest divergent lineage and the mosses as sister to a crown clade formed by the hornworts and polysporangiophytes (lycophytes, monilophytes and seed plants). Alternative topologies resolving the hornworts as sister to mosses plus polysporangiophytes are less well supported. Sporophyte development in liverworts depends only on embryonic formative cell divisions. A transient basal meristem contributes part of the sporophyte in mosses. The sporophyte body in hornworts and polysporangiophytes develops predominantly by post-embryonic meristematic activity.

Scope

This paper explores the origin of the sporophyte shoot in terms of changes in embryo organization. Pressure towards amplification of the sporangium-associated photosynthetic apparatus was a major driver of sporophyte evolution. Starting from a putative ancestral condition in which a transient basal meristem produced a sporangium-supporting seta, we postulate that in the hornwort–polysporangiophyte lineage the basal meristem acquired indeterminate meristematic activity and ectopically expressed the sporangium morphogenetic programme. The resulting sporophyte body plan remained substantially unaltered in hornworts, whereas in polysporangiophytes the persistent meristem shifted from a mid-embryo to a superficial position and was converted into an ancestral shoot apical meristem with the evolution of sequential vegetative and reproductive growth.

Conclusions

The sporophyte shoot is interpreted as a sterilized sporangial axis interpolated between the embryo and the fertile sporangium. With reference to the putatively ancestral condition found in mosses, the sporophyte body plans in hornworts and polysporangiophytes are viewed as the product of opposite heterochronic events, i.e. an anticipation and a delay, respectively, in the development of the sporangium. In either case the result was a pedomorphic sporophyte permanently retaining juvenile characters.     

Another evidence for inhibitory effect of auxin in adventitious bud formation of decapitated flax (Linum usitatissimum L.) seedlings

Adventitious buds were formed on the hypocotyls of decapitated flax seedlings. Scanning electron and light microscopic examinations of hypocotyls showed that epidermal cells divided to produce meristematic spots from which several leaf primordia were formed. Between leaf primordia and the original vascular tissues of hypocotyls, new xylem cells were formed which connected them. About 10, 30 and 60% of adventitious buds were formed on upper, middle and basal parts of hypocotyls of decapitated seedlings, respectively. Removal of apical meristem together with longer hypocotyl zero to four cm long below the apical meristem) induced higher percentage of adventitious bud formation in the remaining hypocotyl. When the entire hypocotyl was cut into 16 segments (0.25 cm each) and these segments were cultured on MS medium containing 3% sucrose and 0.8% agar, adventitious buds were mainly formed in the lowest five segments. These results suggested that there was a gradient of inhibitory factor(s) from apical to basal part of hypocotyl with respect to adventitious bud formation. Auxin transport inhibitors, morphactin and TIBA induced adventitious bud formation on intact seedlings by suppressing the basipetal movement of auxin.     

THE FERTILE SPIKE OF OPHIOGLOSSUM PETIOLATUM. I. MECHANISM OF ELONGATION

The frond of Ophioglossum consists of a sterile segment and a fertile segment or spike. An investigation of fertile spike elongation reveals that growth of the spike proceeds by activity of an intercalary meristem located in the most distal region of the peduncle subtending the sporangial area. Anatomical comparisons of all regions of developing spikes, counts of mitotic figures along the length of spikes of various ages, determination of cell lengths of peduncle ground parenchyma cells, and historadioautography of spikes treated with H³-thymidine confirms the presence in the apical portion of the peduncle of a region of frequently dividing cells intercalated between two regions of more mature tissues. Marking experiments indicate that the petiole of the sterile segment of the frond elongates in a similar fashion. Although this type of intercalary meristem is rather common in angiosperm flower scapes and peduncles, this is the first detailed analysis of this type of growth in a pteridophyte genus.     

CIRCANNUAL GROWTH RHYTHM AND PHOTOPERIODIC SORUS INDUCTION IN THE KELP LAMINARIA SETCHELLII (PHAEOPHYTA)1

Growth and reproduction of laboratory-grown sporophytes of Laminaria setchellii Silva were investigated in a tank system with controlled conditions of daylength, temperature, and nutrients (N and P). A circannual growth rhythm of the frond was detected under constant laboratory conditions. In continuous long-day and night-break conditions the period τ of the free-running rhythm varied between 11.3 and 17.3 months; in short-day conditions the frond grew indefinitely. The growth rhythm of individual plants could be synchronized by a simulated annual cycle of day-length with a period of T = 12 months. The four seasons of the year were simultaneously simulated by phase shifting the annual cycle of daylength by 3, 6, or 9 months in three out of four tanks. The annual growth cycle followed these phase shifts, and initiation of the new blade always started just after the winter daylength minimum. The formation of sori was induced by a genuine photoperiodic short-day reaction in 1- to 2-year-old plants. Sori became, visible 9–14 weeks after transfer of individual plants from long-day to short-day conditions, whereas plants cultured in continuous long-day or night-break conditions remained sterile. Sporophytes with or without blades were able to continue growth or produce new blades in continuous darkness.     

Microlepia boluoensis sp. nov. (Dennsteadtiaceae) from Guangdong,China

Microlepia boluoensis Y. Yuan & L. Fu, a new species of the genus Microlepia from Luofu mountain, Boluo county, Guangdong province, China, is described and illustrated. Its gametophytic chromosome number is n =47. Microlepia boluoensis has a similar morphology to M. scyphoformis, M. speluncae and M. hancei, such as creeping rhizomes, bipinnate‐tripinnatified laminas, intramarginal sori, cup‐shaped indusium and trilete spores, but it has a shorter creeping rhizome, larger frond (up to 351 cm), dry chartaceous, longer stipe (up to 139 cm), 23 pairs of primary pinnae, 1–13 sori, and spores with a distinct and raised laesurae.     

Isolated, distal blade discs of the brown alga Laminaria digitata form sorus, but not discs, near to the meristematic transition zone

Blade discs of vegetative thalli of Laminaria digitata (Huds.) Lamour. from Helgoland (North Sea) cut at 5–15 cm distance from the blade/stipe transition, formed sorus in the laboratory after 7–12weeks, 5 months earlier than whole fronds in the field. Sorus formation occurred in a broad range of daylength regimes or temperatures, at 8–16 h light pe rday and 6–12 ^°C. No sorus was developed during three months by meristematic blade discs cut from the lowermost 3 cm portion of the blade, nor from whole thalli cultured in parallel to isolated blade discs. These findings point to the possible existence of sporulation inhibitors produced by the laminarian meristem. This revised version was published online in August 2006 with corrections to the Cover Date.     

The movements of pikeperch in a shallow reservoir

The movements of 12 female (62–74 cm) and eight male pikeperch (55–64 cm) radiotagged in early March 1997 in the shallow and turbid Bygholm Reservoir, peaked during the summer, but all fish were also active during the winter. Females moved more than males and their activity was correlated with water temperature. Rate of movement was correlated positively with body size for both male and female pikeperch. During the breeding season (April–May) males became stationary for 14–47 days. Spawning sites, inferred from movements of males, were at depths of 2·0–2·5 m on hard substrata, mainly gravel in areas with many submerged trees and shrubs. Males tended to use the same spawning site the next year. Diel activity pattern varied seasonally but activity was highest from 1800 to 2400 hours.     

Crowding in clonal seaweeds: Does self-thinning occur in Mastocarpus papillatus shortly before stand biomass peaks?

Fronds from crowded stands of clonal seaweeds, particularly those in which holdfasts are mostly perennial and are the major source of new fronds every year, are thought not to undergo self-thinning during the growth season, unlike those from crowded stands of unitary seaweeds. For clonal seaweeds, it is not known, however, what happens at the very end of the growth season, when crowding is highest for the year. By sampling twice more frequently than previously done for similar species, the possible occurrence of frond self-thinning was tested for Mastocarpus papillatus (Rhodophyta, Gigartinales, Petrocelidaceae) from western Canada during the growth season (spring) of 2003. Initially, stand biomass increased together with frond density, as found previously for similar clonal seaweeds. Shortly before stand biomass peaked for the year (June), frond density remained statistically unchanged. Thus, the increased sampling precision of this study confirms that fronds of these clonal seaweeds do not undergo self-thinning, not even shortly before crowding is highest. Frond size inequality for M. papillatus remained statistically similar during the growth season, which is also consistent with a model of no self-thinning. There are similarities in biomass–density dynamics and in size inequality dynamics between clonal seaweeds and clonal vascular plants.     

COMPLEX PALEOZOIC FILICALES IN THE EVOLUTIONARY RADIATION OF FERNS

Filicalean frond segments bearing indusiate sori with gradate development have been discovered in Pennsylvanian deposits of eastern North America. The specimens combine characters of Schizaeaceae, Gleicheniaceae, Cyatheaceae and Hymenophyllaceae, and together with data from other sources, indicate that the Filicales were in the midst of an evolutionary radiation during the late Paleozoic. Evidence from fossil and extant species prompts the hypothesis that filicalean ferns originated near the base of the Carboniferous, and have undergone three major evolutionary radiations.     

Fecundity,spore recruitment and size in Gelidium sesquipedale (Gelidiales,Rhodophyta)

Gelidium sesquipedale fecundity was quantified by counting tetrasporangial sori and cystocarps per meter squared and by estimating the number of spores contained inside them. These were obtained by regression on a size metric of reproductive structures. Tetrasporangial sori length and cystocarp thickness were the best estimators of spore number. To assess spore recruitment, 12 pottery tiles were fixed to the bottom, and the appearance of small fronds was monitored.No clear seasonal pattern of reproduction was found. Tetraspore production peaked in March 1990 with 10.4 × 10⁶ spores m^–2, whereas the carpospore peak was lower, 4.9 × 10⁵ spores m^–2 in July 1989. Recruitment followed tetraspore peaks. The probability of a G. sesquipedale tetraspore making the transition to a recruit was 4.7 × 10^–5. Frond length was significantly related to tetrasporangial sori number, while cystocarp number was only related to frond branching order. Minimum size for reproduction was 6.9 cm for gametophytes and 5.4 cm for tetrasporophytes; very rarely were cystocarpic fronds smaller than 9 cm, while tetrasporic fronds were often longer than 15 cm. Cystocarpic fronds were significantly shorter and had more branches than tetrasporic fronds.     

A new late Westphalian fossil marattialean fern from Nova Scotia

Sydneia manleyi gen. et sp. nov. is based on part of a fertile frond from the upper Westphalian D of the Sydney Coalfield, Nova Scotia, Canada. It has small synangia composed of laterally fused sporangia that are elongate and with a circular cross-section. The sporangia yielded variably sized monolete and trilete spores with laevigate and microspinate ornamentation; intermediate forms were also observed. The spores can be correlated with the sporae dispersae species Latosporites minutus , Punctatosporites oculus and Laevigatosporites minimus . Size distribution of the spores is variable and highly skewed, suggesting heterogeneity of the spores within the sporangium. Spore ultrastructure indicates that the fossil is part of a fern, and the morphology of the spores and synangia indicate marattialean affinities.  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society , 2003, 142 , 199–212.     

Flow and polypide distribution in the cheilostome bryozoan Bugula and their inference in Archimedes

Cilia-generated flow in the absence of ambient current is directed from frontal to reverse sides of branches in Bugula turrita, B. turbinata, B. neritina , and B. stolonifera , whether axes of feeding lophophores are perpendicular to the basal plane of branches or are tilted toward distal ends of branches. Ambient current less than 5 cm per second interacts with cilia-generated flow, but ambient flow of 15 cm per second destroys self-generated colonial flow and severely hampers feeding. Polypides are located in the more distal, younger portions of colonies, in species with and without polypide recycling, whereas zooids in the more proximal, older portions are senesced. Presence of feeding polypides in distal but not in proximal portions of the larger spiralled colonies of B. turrita and B. turbinata results in downward, slightly radially directed flow through the colony. The colonial flow passes directly from one whorl to the next-proximal so that water exits from low around the colony perimeter, and a proximally expanding conical stagnant zone occupies the interior of the colony. A substantial percentage of zooecia in distal whorls of well-preserved Archimedes is filled by sediment and inferred to have been occupied by actively feeding polypides. whereas spar-filled zooecia capped by terminal diaphragms were apparently senesced during the latter part of a colony's existence. The capped zooecia constitute an increasing percentage of the total in more proximal whorls. Generally similar colony form and inferred similarity in distribution of current-generating polypides in spiralled colonies of Bugula and in Archimedes suggest that colony-generated flow in Archimedes was similar to that in Bugula , passing downward and then outward, and only through the distal whorls of the colonies.     

DEVELOPMENT OF PROTOPLASTS OF ULVA FASCIATA (CHLOROPHYTA) FOR ALGAL SEED STOCK

The aim of this study was to isolate and cultivate protoplasts of the green alga Ulva fasciata Delile and subsequently induce them to form a microthallus suspension for algal seed stock. The protoplasts were covered with secreted mucilage following 6 h of culture when viewed with SEM. The mucilage fused to form thick layers during day 1 of culture. Microfibrillar cell walls were deposited into the thick layers of mucilage on the 5th day of culture. An average of about 10% of the freshly isolated protoplasts began to divide at 6–14 days. These protoplasts subsequently developed varied morphologies, depending on the time of collection during the year. Protoplasts isolated from U. fasciata collected in March to June developed frond thalli or microthalli when they were cultured in low or high densities (cells/area), respectively. The microthallus suspension was cultured for more than two years at 10–40 μ mol·m^{− 2} ·s^{− 1} . Frond thalli formed when the suspension was cultivated at 100–160 μ mol·m^{− 2} ·s^{− 1} . Therefore, microthallus suspension can serve as a seed stock of U. fasciata .     

Ultrastructure of Draparnaldia glomerata (Chaetophorales, Chlorophyceae). 1. The flagellar apparatus of the zoospore

The fine structure of the quadriflagellate zoospores of Draparnaldia glomerata (Vauch.) Agardh is described with emphasis on the flagellar root system and compared with the flagellar apparatus of related green algae. It is demonstrated that the flagellar root system in Draparnaldia is similar to that of the zoospore of Uronema belkae. Common features include presence of a cruciate root system (formula 2–5–2–5), prominent striated distal fibre connecting opposite basal bodies, a system I striated root component associated with the 2–stranded root, association of electron dense material with the 5–stranded root, mode of arrangement of the basal bodies in the absolute configuration model, and presence of four striated peripheral fibres interconnecting adjacent basal bodies. Differences exist in the shape of the striated peripheral fibres, the origin of the 2– and 5– stranded roots in the proximal part of the flagellar apparatus, and the architecture and striation pattern of the proximal part of the system I fibre that detaches from the 2–stranded root between adjacent basal bodies. Both the 2– and 5–stranded roots originate near the basal bodies and descend deeply into the zoospore. One of the 5–stranded roots passes near the eyespot of the chloroplast. The implications of these findings for the taxonomic position of the genus Draparnaldia are discussed. In addition, an evaluation is given of the present status of the order Chaetophorales. Suggestions are given to standardize some aspects of the current terminology of the cruciate flagellar root system in green algae.     

TRANSLOCATION OF IODINE IN LAMINARIA SACCHARINA(PHAEOPHYTA)1

Long-distance translocation of ¹²⁵I in Laminaria saccharina (L.) Lamour. followed a “source to sink” pattern. When the source of ¹²⁵I was placed on the distal mature part of the blade, the translocation was unidirectional, basipetal and directed towards the meristematic region at the blade-stipe junction. When the source was placed directly at the meristem there was no movement of label distal to the meristem. The velocity of¹²⁵I transport ranged from 2 to 3.5 cm · h^?1. The anion I^? seemed to be the only species of¹²⁵I transported. An assay of iodine content in different parts of L. saccharina plant showed much higher levels of iodine in the meristem, stipe and holdfast than in the blade. This distribution concurs well with the pattern of I^? translocation.