Phenology of 16 species of ferns in a subtropical forest of northeastern Taiwan

A knowledge of fern phenology promotes understanding of the biology and ecology of ferns. In this study, the phenology of 16 fern species in a subtropical broadleaf forest (N24°46′, E121°34′) in northeastern Taiwan was monitored from August 1997 to August 2001. Every fern produced both fertile and sterile leaves in each year of the study. Most fertile leaves emerged in February and March, whereas most sterile leaves emerged from May to September. Most leaves reached full expansion during April–July and died during April–August. The average life span of leaves ranged from 4.4 months to 30.3 months. In seven species, fertile leaves lived longer than sterile leaves, but this difference was significant only in Pteris wallichiana. In the other nine species, sterile leaves lived longer than fertile leaves, but the difference was significant only in Cyathea spinulosa, Plagiogyria dunnii, and Plagiogyria adanata. The ephemeral fertile leaves of the two dimorphic species died soon after releasing their spores, at only 5 months of age. However, their sterile leaves survived for over 22 months. The fertile leaves of the other 14 species remained green for almost 2 years after releasing their spores. Sterile leaves remained sterile throughout their lives. Spores matured in May–July and were released in June–August. After spore release, the sporangia detached. No leaf produced a second cohort of sori. Several phenological events, including sterile leaf emergence, leaf expansion and senescence, and spore maturation and release, were significantly positively correlated with temperature but not with precipitation, whereas the emergence of fertile leaves was weakly negatively correlated with temperature and precipitation. However, those correlations varied among different species. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Leaf growth and demography of the rheophytic fern Thelypteris angustifolia (Willdenow) Proctor in a Puerto Rican rainforest

Morphological and temporal aspects of the growth of leaves of Thelypteris angustifolia (Willdenow) Proctor are under study along a 400-m section of the Sonadora River at the El Verde Field Station in the Luquillo Experimental Forest of Puerto Rico. Emergence, expansion and growth of leaves of 149 sporophytes have been observed approximately mid-month every January, May and September since September 1991. Results of the first four years of this long-term study of T. angustifolia are reported here. Although they are land plants, sporophytes of T. angustifolia are rheophytic, subject to intermittent flooding and submerged approximately 7% of the time. The pinnate leaves of T. angustifolia exhibit sterile-fertile leaf dimorphy. Only 7.6% of the leaves in the the sample were fertile. The petiole of a fertile leaf was 41% longer than that of a sterile leaf while leaf blades were the same length. Leaves expanded at a mean rate of 1.7 cm per day, maturing in 29.7 days. Mean leaf life span was 10.8 months with a maximum of 26 months. Sterile leaf longevity (11.0 months) was longer than that of the fertile leaf (9.6 months). Leaves were produced at a mean rate of 4.7 leaves per plant per year. Leaf damage occurred on 38% of the leaves observed. Net leaf counts for individual sporophytes ranged from one to eight with a mean of 3.0 leaves per plant. Fertile plants had higher mean leaf counts (4.1) than plants without fertile leaves (2.8). Leaf production, although possibly triggered by increasing daylength, also paralleled seasonal increases in rainfall during the wetter mid-May/September months. Increased leaf mortality occurred during the drier mid-January/May period.     

Experimental Studies of the Factors Controlling Transpiration: II. THE RELATION BETWEEN TRANSPIRATION RATE AND LEAF WATER CONTENT

Data are presented which show, when stomatal control is eliminated,that wheat leaves may lose 5–6 per cent. and Pelargoniumleaves 10–12 per cent. of their water without any reductionin the transpiration rate. Experiments in which Pelargonium and wheat leaves, with stomatalcontrol present, were submitted to cycles of changing watercontent also failed to establish any direct relation betweentranspiration rate and leaf water content. It is concluded that leaf water content over the range of 70–100per cent. of that present in the turgid state has no significanteffect in determining the rate of water loss from leaves. A repetition of Knight's experiment showed that stomata openedin still air and closed in moving air. This was not recordedby Knight, who used a porometer cup permanently attached tothe leaf. It is concluded that the higher transpiration raterecorded by Knight after a period of still air was due to widerstomatal aperture and not to the higher leaf water content assuggested by him.     

Effects of Nitrogen Nutrition on Leaf Expansion and Photosynthesis of Trifolium subterraneum L. 1. Comparison between Different Levels of Nitrogen Supply

Growth analysis showed that reductions in the relative growth-rateof subterranean clover plants (cv. Mt. Barker), even those dueto moderate nitrogen deficiencies, were reflected in reductionsof the leaf-area ratio and particularly of the net assimilationrate. A decline in nitrogen supply in the culture solutions was foundto depress net rates of carbon dioxide uptake per unit leafarea and leaf expansion per plant to about the same extent,even at moderate levels of nitrogen stress. Four days aftertransfer of plants grown with adequate nitrogen to solutionswithout nitrogen, leaf area and net carbon dioxide uptake haddeclined to 84 per cent and 89 per cent of the values for thecontrol plants. After a further 4 days these values had decreasedto 71 per cent and 52 per cent respectively. When net carbon dioxide uptake was expressed per unit weightof chlorophyll, the effect of changes in nitrogen supply onnet photosynthesis largely disappeared, indicating a close relationshipwith the chlorophyll content of the leaves. However, anotherand perhaps more direct effect of nitrogen on photosynthesiswas suggested by the fact that, during the early stages of recoveryfrom a severe nitrogen stress, photosynthesis began to increasebefore the chlorophyll content of the leaves.     

Isolated Megaspore Tetrads of Stauropteris burntislandica

A new type of fossil spore tetrad, Didymosporites scotti gen.et sp. nov. is described from the Dinantian and Namurian (Carboniferous)of Ireland, Scotland, and England. The spores always occur inthe form of a tetrad composed of two large (presumably fertile)and two minute (presumably abortive) spores, all with cutinizedwalls. Reasons are given for regarding these as the megasporesof the coenopterid fern Stauropteris burntislandica; their distributionindicates a far wider range in time and space than that previouslyknown for this species. Their occurrence as adhering tetradssuggests that Stauropteris burntislandica 'shed' its megasporesstill enclosed in the sporangiumIan interesting analogy withboth Lepidocarpon and the seeds of Pteridosperms.     

Studies in the Nutrition of Apple Rootstocks: II. Effects of Concentration of Iron in the Nutrient Solution on Growth and Chlorophyll Content

Rooted one-year shoots were grown for one season by sprayingtheir roots with nutrient solution. Iron supplied as Fe-EDTAat four concentrations resulted in plants which were respectively(a) severely chlorotic, (b) mildly chlorotic, (c) dark greenand healthy (controls), and (d) dark green but with slight reductionin growth. Severely deficient plants showed 40–70 per cent reductionsin growth as measured by fresh weight, shoot length, diameterincrease, leaf area, net assimilation and relative growth-rates.Dry weights were reduced 70–80 per cent and of the totaldry-weight increment a greater proportion remained in the leaves,which had a lower dry weight and higher water content per unitarea. However, because the initial old stem formed a greaterproportion of the total dry weight, the leaf area ratio remainedabout 11 per cent lower than in the controls. Severely deficientplants had, per unit of chlorophyll, a higher dry-weight increaseand net assimilation rate than the controls. Mild deficiency caused 10–20 per cent reductions in growthand net assimilation rate; the leaf area ratio was normal. Possible mechanisms of the effects of low iron supply are discussed,while the small growth reduction at the highest Fe-EDTA concentrationis attributed to chelate toxicity     

Cell Division and Expansion in the Growth of the Leaf

Volumes and numbers of cells were determined at different stagesof development of the fifth leaf of Lupinus albus, and eachof the second pair and the tenth leaf of Helianthus annuus.In the case of the second pair of sunflower leaves the valuescover the whole life of the leaf from initiation to senescence. During both primordial development and the ensuing ‘grandperiod of growth’ division is the determinant of growth.About 10 per cent. of the cells in the fully grown leaf arelaid down before leaf-emergence; the remaining 90 per cent.are formed during unfolding. Division does not cease in thelupin leaf or the second pair of sunflower leaves until theyhave reached half their maximum area. The tenth leaf, on theother hand, is as much as three-quarters fully grown beforedivision ceases. Cell expansion commences soon after leaf initiation and continuesthroughout the life of the leaf. With lupin and the second pairof sunflower leaves there is a fourfold increase in the averagevolume of the cells before emergence from the apical region.During unfolding, there is a further tenfold increase in theaverage volume of the cells of the lupin leaf, and a twentyfoldincrease with the second pair of sunflower leaves. Expansioncontinues after the cessation of division but this further increasein volume is comparatively small. The data are discussed in relation to the ‘two phase’hypothesis of leaf development.     

The Production and Distribution of Dry Matter in Maize after Flowering

An experiment in which different groups of leaf laminae wereremoved, or ears shaded, shortly after silking showed that mostof the dry-matter increase after flowering was produced by upperleaves. The top five, the middle four, and the bottom six laminaeaccounted, respectively, for 26 per cent, 42 per cent, and 32per cent of the leaf area duration (D) of the laminae afterflowering; the estimated contributions of the three groups todry-matter production by the laminae after flowering were about40 per cent, 35–50 per cent, and 5–25 per cent,respectively. The sheaths provided about one-fifth of the totalleaf area and probably contributed about one-fifth, and laminaefour-fifths, of the total dry matter produced after flowering.The contribution from photosynthesis by the ear was negligible,presumably because its surface area was only 2 per cent of thatof the leaves. Leaf efficiency (dry matter produced per unitarea) decreased greatly from the top to the base of the shoot.When laminae were removed, the grain received a larger fractionof the dry matter accumulated after flowering, less dry matterremained in the stem, and the photosynthetic efficiency of theremaining leaves was apparently increased. When alternate laminae were removed at the time of silking (half-defoliation)D was decreased by 40 per cent, and the subsequent productionof dry matter decreased nearly proportionately, so that netassimilation rate (E) was not affected but grain dry weightwas decreased by only 32 per cent. At the final harvest, thegrain of half-defoliated plants constituted 80 per cent of thedry matter accumulated after flowering, compared with 65 percent for intact plants. Stem weight decreased from two weeksafter flowering in half-defoliated plants, but remained nearlyconstant in intact plants. When pollination was prevented andno grains formed, E during the first month after flowering wasunaffected; the dry matter that would have passed into the grainaccumulated in the stem and husks, not in the leaves. The decrease in stem weight caused by defoliation suggests thatpreviously stored dry matter was moved to the grain. That suchmovement is possible was shown by keeping prematurely harvestedshoots in the dark for two weeks with their cut ends in water;the dry weight of the grain increased and that of the stem,laminae, husks, and core decreased. Nevertheless, dry-matterproduction after flowering was more than sufficient for graingrowth, and previous photosynthesis probably contributed littleto the grain.     

Gibberellin-induced Fertility in the Fern Ceratopteris thalictroides (L.) Brongn

Treatment of the homosporous fern Ceratopteris thalictroides L. sporophyte with gibberellic acid results in fertile fronds appearing 3 to 5 weeks after treatment. The hetero-blastic leaf sequence is markedly reduced, and the entire life cycle can be completed in 3 months on defined medium. Treatment with gibberellic acid also stimulates the accumulation of starch in mature leaves.     

Mineral Depletion and Leaf Senescence in Soya Bean as Influenced by Foliar Nutrient Application During Seed Filling

Senescence, as judged by the time courses of leaf lamina photosynthesis,soluble protein and chlorophyll contents, was studied in relationto mineral redistribution in field-grown soya beans [Glycinemax (L.) Merr] to investigate the hypothesis that the depletionof nutrients m the leaves by the developing seeds is the causeof soya bean senescence. A mineral nutrient solution was appliedto the canopy during the seed-filling period, and the effectson senescence and mineral depletion of the leaves were determinedin three cultivars, at two leaf positions, weekly from beginningof seed filling through physiological maturity. The onset of senescence occurred shortly after the beginningof rapid seed filling Photosynthetic rate declined about 60per cent within 3 weeks. Protein dropped by 52 per cent andchlorophyll by 48 per cent over the same period. Foliar nutrient application, at a rate previously shown to givesignificant yield increases in soya beans, increased the concentrationsof N, P and K in the leaf laminae, but tended only to delaytheir decline and failed to either delay the onset or alterthe course of senescence. The results of this experiment seem to indicate that, undernormal growth conditions, the events of senescence in the soyabean are not causally related to the N, P or K concentrationsof the leaf laminae Glycme max (L.) Merr., soya bean, nitrogen, phosphorus, potassium, leaf protein, chlorophyll, photosynthesis, foliar nutrient application, mineral depletion, leaf senescence     

Leaf Growth in Phaseolus vulgaris: I. Growth of the first pair of leaves under constant conditions

The growth of the first pair of leaves of Phaseolus vulgaris(French bean) has been studied during germination and followingemergence of the seedling. The leaves are well developed inthe embryo and, at 22.5° C, show an exponential increasein fresh weight, dry weight, and leaf area up until about eightdays from planting. Cell division commences about two days afterplanting and is exponential for a short period. Considerablechanges in cell volume occur during the period over which celldivision occurs. Cell division ceases soon after emergence andunfolding, when the leaf has reached only 17 per cent of itsfinal area. Cessation of cell division is followed by a phaseof growth which is due entirely to cell expansion. The significanceof these findings is discussed in relation to recent work onother genera.     

Nitrogen Deficiency in Small Closed Communities of S24 Ryegrass. II. Changes in the Weight and Chemical Composition of Single Leaves During Their Growth and Death

Small communities of S24 ryegrass were grown under supplementarylights in a glasshouse at 20°C, and abundantly suppliedwith a complete nutrient solution containing 300 p.p.m. of nitrogen,until they had a leaf area index of 5 and were fully light intercepting.Half were then given a solution containing only 3 p.p.m. ofnitrogen (LN) while the rest were kept at 300 p.p.m. (HN). The HN plants subsequently produced marginally more leaves,which elongated more rapidly to a greater final length and area,on a third more tillers than did the LN plants. Leaves 5, 6 and 7 on the main stem were examined in more detail.In both the HN and the LN plants the d. wts of both laminaeand sheaths fell by about 30 per cent between their full expansionand death. Changes in acid extractable carbohydrate (AEC) verylargely accounted for the changes in leaf weight, particularlyin the LN plants. With increased nitrogen deficiency, AEC contentsrose from less than 10 per cent for leaf 5 to peak values of20 and 45 per cent for the lamina and sheath of leaf 7, as against10 and 15 per cent in the nitrogen sufficient leaves. Conversely,the nitrogen content of the deficient plants fell from valuesof 5·8 and 4·8 per cent for the lamina and sheathof leaf 5 to 3·0 and 1·2 per cent for leaf 7.It was striking that while the HN leaves lost nitrogen onlywhen they aged and died, the LN leaves started losing nitrogenbefore they had reached full expansion—70 per cent ofthe N initially present was remobilized by the time the leaveswere dead. The significance of these findinp to estimates of leaf deathand total biomass production in the field, and to our understandingof the achievement of ceiling yield, are discussed. Luliwn perenne, S24 ryegrass, carbohydrate content, nitrogen content, nitrogen deficiency     

Chlorophyll Content and the Pattern of Yellowing in Senescent Leaves

In senescent leaves of four species, leaf chlorophyll contentwas approximately linearly related to the estimated area ofyellow tissue, but the species differed in the amount of chlorophylllost before yellowing became apparent. Cotoneaster and Vicia leaves and Sinapis cotyledons, which produceddistinct yellowing patterns lost about 40 per cent, whereasSolanumleaves, which yellowed more uniformly lost over 60 percent of the chlorophyll before yellowing was visible. It issuggested that the leaf-cell population of Solanum may senescerather more synchronously than the other species, and that chlorophyllloss before yellowing may be a useful index of synchrony ofsenescence in leaves.     

Vascular Organization and some Aspects of the Morphology of the Rhizome of Gymnogrammitis dareiformis

Gymnogrammitis dareiformis, the taxonomically controversialdavalliaceous fern has a parenchymatous rhizome, in the groundtissue of which groups of 1–16 thick-walled cells (withpeg-like protrusions on inner walls) are irregularly scattered.Paleae clothing the rhizome are basally attached, gland-tippedand bearing unicellular marginal hairs. The vascular cylinderis a radially-symmetric dictyostele dissected by spirally-arrangedleaf gaps into slender reticulated meristeles. Some of the dorso-laterallyplaced leaves alone are fully developed; most other leaves aresuppressed and some are highly reduced (the larger reduced leavesappear as protrusions on the rhizome and have a well-formedleaf base). The leaf trace of developed as well as the largerreduced leaves is a channel-shaped loose reticulum of four vascularstrands; the trace of the reduced leaves is smaller and endsblindly at the leaf base. The leaf trace of the smaller reducedleaves is vestigial and represented often by only a pair ofvascular strands fusing into one and ending blindly in the cortexof the rhizome. The leaf trace of suppressed leaves fuses backwith the stelar cylinder, forming a convex reticulum bridgingthe sides of the leaf gap. It is suggested that the characteristic stelar organizationof the Davalliaceae is derived by suppression of leaves froma radiallysymmetric dictyostele with spirally-arranged leafgaps as found in Nephrolepis and that Gymnogrammitis with itsreduced and suppressed leaves indicates the process of transition.The creeping solenostelic rhizome with two-ranked leaf arrangementcould be derived from an erectgrowing dictyostelic one by supppressionof leaves.     

Effects of Population Density on Sex Expression in Onoclea sensibilis L. on Agar and Ashed Soil

Population density affected the sex expression of agar-growngametophytes of Onoclea sensibilis L. The time of onset of sexualitywas advanced, the proportion of females was increased, and thegrowth rate of individuals was greater at lower densities. Populationdensity had no effect on the sex expression of Onoclea grownon ashed soil, and there was no difference in growth rate ofindividuals grown on ashed soil at different densities. Covariateanalysis, using thallus width as a measure of growth rate, indicatedthat the effect of density on sex expression was mostly associatedwith growth rate. The differing effects of population densityon agar and ashed soil demonstrate that substrate influencessex expression in Onoclea. This influence is most dramatic insingle-gametophyte cultures, where agar cultures produced 97per cent females and ashed soil cultures 100 per cent males. Onoclea sensibilis L., sensitive fern, fern gametophytes, sexuality, population density     

Patterns of 14C-labelled Assimilate Partitioning in Red and White Clover During Vegetative Growth

A quantitative analysis of the ¹⁴C-labelled assimilate suppliedby the expanded leaves on the primary shoot to growing leaves,stem, lateral shoots (branches or stolons) and roots in redand white clover was conducted during vegetative growth. Stem growth of the primary shoot was inhibited in both cloversand utilized no energy resources. The growing leaves at theprimary shoot apex of white clover imported 4 per cent of theshoot's assimilate compared with 10 per cent in red clover.At the basal end of the primary shoot, the tap root of whiteclover imported 16 per cent of the shoot's assimilate comparedwith 22 per cent in red clover. Branches in red clover and stolonsin white clover were by far the largest sinks for primary shootassimilate, importing 39 per cent and 63 per cent of the labelledassimilate, respectively. Analyses of the translocation of assimilate from individualprimary shoot leaves demonstrated that in both clovers olderleaves exported more of their assimilate to branches or stolons,whereas younger leaves exported more of their assimilate toroots, and possibly in white clover, to growing leaves at thetip of the shoot. Of the labelled assimilate exported to branchesor stolons, each primary shoot leaf exported preferentiallyto the branch or stolon in its own axil, but in addition exportedsubstantial quantities of assimilate to all other axillary shoots,particularly those arising from basal axils where the subtendingleaf had died. Trifolium repens, Trifolium pratense, red clover, white clover, assimilate partitioning, perennation     

Effects of Age and Gibberellic Acid on the Flavonol Content of Pisum sativum Leaves

Changes in the content of quercetin and kaempferol during leafdevelopment in Pisum sativum cv. Meteor are described. As theleaves matured the quercetin content decreased and that of kaempferolincreased during a period from 37 to 48 days from planting.Maximum flavonol content per leaf was found in leaves higheron the shoot as development proceeded, but total leaf flavonolcontent per plant remained relatively constant. There was noevidence to suggest that the quantitative changes in the individualflavonols were the result of conversion of quercetin into kaempferol. Treatment with gibberellic acid led to an accelerated fall inquercetin content in the mature leaves. This change was detectable24 h after treatment and before any apparent growth response.     

First report of fern (Culcita macrocarpa) spore consumption by a small mammal (Apodemus sylvaticus)

Few vertebrates are known to consume ferns regularly. Several species of mammals consume leaves to some extent but the consumption of fern spores is much rare. In Galicia (Northwest Spain) we studied the seasonal variation in the consumption of Culcita macrocarpa fertile leaves (i.e. with spores) in two populations (Capelada and Eume), assessed whether consumption rate increased with fern population size, and evaluated whether the consumer was a spore predator or a spore disperser. Consumption began in December and finished by mid February, and occurred before spore release, which happened later in Capelada than in Eume, probably influenced by differences in altitude. The consumer was identified as Apodemus sylvaticus by DNA analysis of its droppings and by capture of live animals. Throughout Galicia there was a significant increase in fern consumption rate as the population size of C. macrocarpa increased. Germination tests from droppings were carried out in 14 dishes but only in two dishes 1% and 0.3% of the spores germinated. Our results suggest that woodmouse can disperse spores of C. macrocarpa, although most of the spores were digested.     

Effects of Airspeed and Humidity Changes on Spore Discharge in Sordaria fimicola

An improved experimental system is described for studying therate of spore discharge in Sordaria fimicola subjected to anair-stream of controlled rate and relative humidity. Under nearlysaturated conditions the rate of air-flow does not seem to affectthe rate of discharge. Reduction of the R.H. from 95 per centto 70 per cent or 35 per cent leads to an immediate but temporaryincrease in discharge rate. 70 per cent R.H. seems only to affectactual discharge, but prolonged exposure to 35 per cent R.H.interferes as well with earlier stages in spore development.It is suggested that the immediate effect on discharge is physicalrather than biochemical. There is evidence that the perithecialwall plays some part in the control of spore discharge.     

Cellular Structure and Light Absorbtion in Leaves of Frithia pulchra (Mesembryanthemaceae)

In order to quantify the structural differences between celltypes of leaves from a ‘ window’ plant, an ultrastructuralmorphometric analysis was made of the epidermal, window andchlorenchyma tissues of Frithia pulchra. Epidermal cells arethe largest cells found in Frithia leaves and are characterizedby the presence of a thick outer tangential cell wall and numerousvacuolar inclusions. Epidermal tissue has an optical densityof 0.30. The transparent window tissue (i.e. optical density= 0.08) has a uniform ultrastructure throughout the length ofthe leaf. The vacuome comprises aproximately 97 per cent ofthe protoplasmic volume of window cells. Chlorenchyma cellspossess thin cell walls and are surrounded by numerous intercellularspaces. Cells of the apical chlorenchyma tissue possess approximately30 plastids per cell. These chloroplasts have an average individualvolume of 220 µm². Cells of the basal chlorenchyma tissuecontain chloroplasts that are five to six times smaller andmore numerous than those in cells of the apical chlorenchyma.The increased volume of chloroplasts in the apical comparedwith basal chlorenchyma cells (i.e. 31.4 and 20.2 per cent ofthe protoplasm, respectively) is positively correlated withtheir optical densities of 1.46 and 0.97, respectively. Frithia pulchra, stereology, leaf, light absorption, window plant