Cytochemical and ultrastructural aspects of aquatic carnivorous plant turions

Turions, which are modified shoot apices, are vegetative, dormant overwintering organs produced by perennial aquatic plants. In this study, the turion cytochemistry and ultrastructure of Aldrovanda vesiculosa, Utricularia vulgaris and U. stygia were compared with particular emphasis placed on storage substances. These three aquatic, rootless carnivorous plant species were studied at the end of their winter dormancy. At this stage, the turions of all species had starch as their main storage material. In contrast with A. vesiculosa, Utricularia turions were rich in protein storage vacuoles, and proteins were also accumulated as crystalline inclusions in the nuclei. All examined species accumulated lipid droplets in cells of epidermal glands.     

Increases in Phosphorus Requirements for CO(2)-Enriched Pine Species

Pinus radiata D. Don (half-sib families 20010 and 20062) and Pinus caribaea var hondurensis (an open-pollinated family) were grown for 49 weeks at seven levels of phosphorus and at CO₂ concentrations of either 340 or 660 microliters per liter, to establish if the phosphorus requirements differed between the CO₂ concentrations and if mycorrhizal associations were affected. When soil phosphorus availability was low, phosphorus uptake was increased by elevated CO₂. This may have been related to changes in mycorrhizal competition. When the phosphorus concentration in the youngest fully expanded needles was above 600 milligrams per kilogram the shoot weight of all pine families was greater at high CO₂ due to increases in rates of photosynthesis. More dry weight was partitioned to the stems of P. radiata family 20010 and P. caribaea. At foliar phosphorus concentrations above 1000 milligrams per kilogram (P. radiata) and 700 milligrams per kilogram (P. caribaea), growth did not increase at 340 microliters of CO₂ per liter. Soluble sugar levels in the same needles mirrored the growth response, but the starch concentration declined with increasing phosphorus. At 660 microliters of CO₂ per liter, shoot weight and soluble sugar concentrations were still increasing up to a foliar P concentration of 1800 milligrams per kilogram for P. radiata and 1600 milligrams per kilogram for P. caribaea. The starch concentrations did not decline. These results indicate that higher foliar phosphorus concentrations are required to realize the maximum growth potential of pines at elevated CO₂.     

Localization of starch in shoot apices of vegetative and photoperiodically induced plants ofChenopodium rubrutn

Starch was determined by means of IKI reaction in shoot apices ofChenopodium rubrum plants induced to flowering by two short days and in non-induced plants. Small starch grains were already observed in the meristematic cells at an age of four days after sowing. Larger grains were found in the subapical region of the apex. Heterogeneity increases during further growth of the plants in induced, as well as in non-induced vegetative plants. Starch disappears from the cells potentially giving rise to axillary buds, while the number and size of starch grains increase in cells from which leaf primordia will be formed. This metabolic specifity of leaf and bud primordia is preserved during morphological differentiation and applies to vegetative, as well as to prefloral apices of photoperiodically induced plants. The amount of starch in the different regions of the apex is linked rather with organogenesis than with the quantitative growth in the apex.     

In vitro induction of multiple shoots and plant regeneration inVigna

Summary Cotyledonary nodes, excised cotyledons, and hypocotyl segments of six varieties ofVigna mungo andV. radiata have been tested for their morphogenic potential on media containing a range of hormonal combinations including benzyladenine, kinetin, thidiazuron (TDZ), and zeatin. Multiple shoots developed on cotyledonary node explants in all varieties tested on basal medium containing cytokinin. Presence of both the cotyledons, either full or half, resulted in a maximum number of shoots produced. Shoot bud regeneration was achieved via meristem formation on excised cotyledons on Murashige-skoog basal medium with B₅ vitamins supplemented with TDZ. Mature plants had normal phenotypes.V. mungo var. PS1 andV. radiata var. Pusa 105 were found to be the most responsive varieties for shoot regneration. The histology ofin vitro organogenesis was studied.     

SYMMETRY AND DEVELOPMENT OF BUTOMUS UMBELLATUS (BUTOMACEAE) AND LIMNOCHARIS FLAVA (LIMNOCHARITACEAE)

The prostrate rhizome of Butomus umbellatus produces branch primordia of two sorts, inflorescence primordia and nonprecocious vegetative lateral buds. The inflorescence primordia form precociously by the bifurcation of the apical meristem of the rhizome, whereas the non-precocious vegetative buds are formed away from the apical meristem. The rhizome normally produces a branch in the axial of each foliage leaf. However, it is unclear whether the rhizome is a monopodial or a sympodial structure. Lateral buds are produced on the inflorescence of B. umbellatus either by the bifurcation or trifurcation of apical meristems. The inflorescence consists of monochasial units as well as units of greater complexity, and certain of the flower buds lack subtending bracts. The upright vegetative axis of Limnocharis flava has sympodial growth and produces evicted branch primordia solely by meristematic bifurcation. Only certain leaves of the axis are associated with evicted branch primordia and each such primordium gives rise to an inflorescence. The flowers of L. flava are borne in a cincinnus and, although the inflorescence is simpler than that of Butomus umbellatus, the two inflorescences appear to conform to a fundamental body plan. The ultimate bud on the inflorescence of Limnocharis flava always forms a vegetative shoot, and the inflorescence may also produce supernumerary vegetative buds. Butomus umbellatus and Limnocharis flava exhibit a high degree of mirror image symmetry.     

Vigna Radiata Seed Germination under Salinity

Salinity reduced mung bean (Vigna radiata Wilczek) radicle and root elongation, delayed and inhibited hypocotyl elongation and mobilization of reserves from the cotyledons to the embryo axis. Fresh and dry masses and water content of the embryo axes were reduced. Under salinity, a net leakage of K to the media increased with time and increasing NaCl concentrations. Sugars present in the cotyledons of seeds were of primary importance for growth of the embryo axis upto 18 h after sowing whereas breakdown of starch by amylase contributed later, the contribution being delayed and reduced with increasing NaCl concentration. Even when amylase activity in the cotyledons was progressively reduced with increasing NaCl concentration, the increasing contents of soluble sugars in the cotyledons indicated that sugars were not limiting for mung bean seedling growth under salinity.     

Vegetative anatomy of Pachycortnus (Anacardiaceae)

Pachycormus discolor , an arborescent desert perennial endemic to Baja California, has small, pinnately compound, hypostomatic, bifacial leaves produced on short shoots and photosynthetic stem phelloderm covered by exfoliating translucent phellem. Tightly packed laminal palisade cells are filled with tannins and lack chloroplasts. Spongy mesophyll is the major photosynthetic tissue. Leaves possess unicellular trichomes with secondary walls and uniseriate trichomes with glandular heads. Schizogenous resin ducts occur in primary phloem of stems, leaves and roots as well as all living tissues of the bark. Developmental studies reveal that initiation and differentiation of foliar primordia resembles that of other dicotyledons except that tannin cells and secretory ducts arise precociously. Primary vasculature is an open sympodial system with three principal traces diverging toward each foliar primordium. The wood is highly specialized and comprises mostly unlignified cells packed with starch grains. Thick bark is mainly produced as annual layers of secondary phloem marked by a ring of secretory ducts each surrounded by tannin cells. The possible adaptive significance of these unusual anatomical features is discussed.     

Chusquea sect. Swallenochloa (Poaceae: Bambusoideae) and allies in Brazil

The 13 high altitude/latitude, dwarf species ofChusquea in Brazil are described, illustrated, and mapped, and their morphology, habitats, distributions, and taxonomic affinities are discussed. Two keys to species are provided, one based solely on vegetative characters, and the other on vegetative and flowering characters.Chusquea erecta, C. nutans, C. riosaltensis,C. windischii, C. caparaoensis, andC. nudiramea are described as new, andC. microphylla is elevated to specific status. Two subspecies are recognized within the variableC. mimosa: C. mimosa subsp.australis and subsp.mimosa. Seven species are formally classified withinChusquea sect.Swallenochloa; the remaining six species are classified into two informal categories, theNudiramea andHeterophylla groups. A list of all the species currently included withinChusquea sect.Swallenochloa is provided.     

Biomass allocation patterns in terrestrial, epiphytic and aquatic species of Utricularia (Lentibulariaceae)

Utricularia forms the largest genus of carnivorous plants and is characterized by the possession of typical traps (“bladders”). Total biomass allocation was examined in three aquatic, six terrestrial and one epiphytic species of Utricularia from natural habitats in West Africa and from the Botanical Gardens, Bonn. Total biomass of aquatic species was considerably higher than that of terrestrial or epiphytic species. Epiphytic Utricularia accumulate about 35% of their biomass in green leaves, in contrast to 65% of nearly chlorophylless reproductive structures and traps. Aquatic species allocated more than 85% of their total biomass to stolons, leaves and traps, but only 10–13% to reproductive structures. This is in stark contrast to the allocation patterns of terrestrial bladderworts. These species allocate nearly 90% of their total biomass in reproductive structures, and only about 10% to stolons, leaves and traps. This reduction of photosynthetically active plant tissue strongly suggests that as a consequence of the alternative resource of chemical energy, the carnivorous habit might have partly replaced autotrophy in certain terrestrial Utricularia species, especially in some smaller ones.     

NaCl effect on the distribution of wall ingrowth polymers and arabinogalactan proteins in type A transfer cells of Medicago sativa Gabès leaves

In most species of the Genlisea–Utricularia sister lineage, the organs arising directly after germination comprise a single leaf-like structure, followed by a bladder-trap/stolon, with the lack of an embryonic primary root considered a synapomorphic character. Previous anatomical work suggests that the most common recent ancestor of Utricularia possessed an embryo comprising storage tissue and a meristematic apical region minus lateral organs. Studies of embryogenesis across the Utricularia lineage suggest that multiple primary organs have only evolved in the viviparous Utricularia nelumbifolia, Utricularia reniformis, and Utricularia humboldtii within the derived Iperua/Orchidioides clade. All three of these species are specialized for growth as “aquatic epiphytes” in the tanks of bromeliads, with recent phylogenetic evidence suggesting the possibility that multiple primary organs may have evolved twice independently within this clade. The primary organs of viviparous Utricularia also possess epidermal surface glands, and our study suggests that these may function as root hairs for uptake of solutes from the external environment—a possible adaptation for the “aquatic–epiphytic” habitat.     

A complex case of simple leaves: indeterminate leaves co-express ARP and KNOX1 genes

The mutually exclusive relationship between ARP and KNOX1 genes in the shoot apical meristem and leaf primordia in simple leaved plants such as Arabidopsis has been well characterized. Overlapping expression domains of these genes in leaf primordia have been described for many compound leaved plants such as Solanum lycopersicum and Cardamine hirsuta and are regarded as a characteristic of compound leaved plants. Here, we present several datasets illustrating the co-expression of ARP and KNOX1 genes in the shoot apical meristem, leaf primordia, and developing leaves in plants with simple leaves and simple primordia. Streptocarpus plants produce unequal cotyledons due to the continued activity of a basal meristem and produce foliar leaves termed “phyllomorphs” from the groove meristem in the acaulescent species Streptocarpus rexii and leaves from a shoot apical meristem in the caulescent Streptocarpus glandulosissimus. We demonstrate that the simple leaves in both species possess a greatly extended basal meristematic activity that persists over most of the leaf’s growth. The area of basal meristem activity coincides with the co-expression domain of ARP and KNOX1 genes. We suggest that the co-expression of ARP and KNOX1 genes is not exclusive to compound leaved plants but is associated with foci of meristematic activity in leaves.     

Identification of the Flower-inducing Factor Isolated from Aphid Honeydew as being Salicylic Acid

Honeydew produced by the aphid Dactynotus ambrosiae when feeding on flowering or vegetative plants of the short day plant Xanthium strumarium contains an active substance capable of inducing flowering in the long day plant Lemna gibba G3. In the present study, this active material has been identified as salicylic acid through the use of gas-liquid chromatography and mass, infrared, and ultraviolet spectrometry. Authentic salicylic acid induces flowering in L. gibba G3 under strict short day conditions with an optimal response at about 5.6 μm. The possible significance of salicylic acid for the control of flowering in Xanthium or L. gibba G3 is discussed.     

Effect of anatomical structure on the buoyancy of achenes of two subspecies ofBolboschoenus maritimus

Differences between two subspecies ofBolboschoenus maritimus (L.)Palla (=Scirpus maritimus L.) in different habitats (littoral and terrestrial) are partly due to variations in the buoyancy of their achenes, caused by different anatomical structure of the fruits. This hypothesis was tested by comparing fruit buoyancy and anatomy of both subspecies at several localities. Plants were sampled fromBolboschoenus maritimus subsp.maritimus (plants with branched inflorescences and triangular fruits, 4 localities) andB. maritimus subsp.compactus (Hoffm.)Hejný (plants with compact inflorescences and prevailing concave fruits, 4 localities) in the Czech and Slovak Republics, andB. maritimus subsp.compactus (plants with compact inflorescences and convex fruits, 1 locality) from the coast of South Sweden. From each locality a plant with several tubers connected by rhizomes was taken and transferred into the experimental garden; from these cultivated plants (clones) mixed samples of fruits collected from each clone were used for buoyancy tests and a study of their anatomy. Fruit buoyancy was found to depend on the anatomical structure of the pericarp—the presence of aeriferous tissue in the exocarp serves as the main floating organ. This differentiated all plants studied into two groups: short-floating subsp.maritimus, with a thin or none acriferous tissue in the exocarp, and long-floating subsp.compactus with well developed aeriferous tissue. Differences in fruit buoyancy corresponds to differences in the prevailing habitat types of both subspecies studied in the inland sites: the frequent occurrence of subsp.compactus in temporarily flooded terrestrial habitats contrasts with the prevalence of subsp.maritimus in the littoral of water bodies. This is an example of intra-specific ecological differentiation leading to differentiation in wetland communities.     

Sieve-element plastids ofCyrillaceae,Erythroxylaceae andRhizophoraceae: Description and significance of subtype PV plastids

A new subtype (PV) of protein-containing sieve-element plastids was found to contain a uniquely large number of polygonal protein crystals, sometimes with (PVcf) and sometimes without (PVc) protein filaments. These plastids do not accumulate starch. The PVcf-plastids occur inCyrillaceae only, while the PVc-plastids are limited toErythroxylaceae andRhizophoraceae. The significance of the new P-subtype with respect to the systematic position of the three families is discussed.     

Giant oil cells in the cotyledons ofPharbitis nil and other convolvulacean plants

Suspension of protoplasts (ca. 13–25 μm in diameter) that were isolated from the mesophyll of the cotyledons ofPharbitis nil, strain Violet, contained many large spherical or spheroidal bodies (ca. 100 μm in diameter). Microscopic observation of these bodies and some anatomic studies of the cotyledons during embryogenesis and after germination showed that these bodies are giant cells containing many oil drops stainable with Sudan dyes. Such giant cells were found in four otherPharbitis nil strains, Nepal, Tendan, Africa and Tokyo-kokei, and in six other Convolvulacean plants,Ipomoea batatas, cv. Koukei-14,Calystegia japonica, Calystegia hederacea, Calonyction aculeatum, Quamoclit pennata andCuscuta japonica.     

Inhibition of Pinus radiata Primary Needle Epicuticular Wax Biosynthesis by Trichloroacetate

High concentrations (1000 parts 10^–6) of trichloroacetate(TCA) inhibit germination of Pinus radiata seed. Seedlings growingin the presence of lower concentrations (100 parts 10^–6)take up TCA where it becomes concentrated in cotyledons anddeveloping primary needles. TCA inhibits biosynthesis of nonacosan-10-oland long chain diol constituents of the primary needle epicuticularwax concomitant with a reduction in appearance of tubular waxexcept around stomatal pores. Epicuticular wax from TCA-treatedplants consists mainly of alkyl esters, and is amorphous. Itis suggested that P. radiata stomatal subsidiary cells possesstubular epicuticular wax chemically distinct from that of epidermalcells.     

Structure, development and evolution of the androecium in Adansonieae (core Bombacoideae, Malvaceae s.l.)

Androecium development and vasculature were studied in nine species of the Adansonieae clade (core Bombacoideae, Malvaceae s.l.). In early androecium development either distinct pentagonal androecial ring walls or five common petal/androecium primordia are present. Ring walls give rise to five antepetalous and five alternipetalous primary androecial primordia. Common primordia divide into peripheral petal primordia and antepetalous primary androecial primordia. Antepetalous primary androecial primordia split anticlinally into ten primordia-halves, on which secondary androecial primordia are initiated in a centrifugal succession. Androecial lobes are formed by fusion of an alternipetalous primary androecial primordium and its two neighbouring antepetalous primary primordia-halves, a pattern that also occurs in other Malvatheca. Later, tertiary androecial primordia are formed by the subdivision of secondary androecial primordia (except in Adansonia and Ceiba). Each tertiary primordium differentiates into a two-locular androecial unit. At anthesis these two-locular androecial units are often present in pairs, corresponding to the two halves of the same secondary androecial primordium. Androecium development and vasculature imply that the alternipetalous androecial sectors have been reduced in Bombacoideae, a tendency that is shared with other subfamilies of Malvaceae.     

Open dichotomous venation in the leaves ofUtricularia striatula (Lentibulariaceae)

The open dichotomous pattern of venation in the leaves ofUtricularia striatula is described in detail and compared withCircaeaster andKingdonia. Similar traits of dichotomous venation occur in other species ofUtricularia and may be due to reduction.Studies on IndianUtricularia, 3.     

Structure of the vegetative shoot apex ofCassiope lycopodioides

The structure of the vegetative shoot apex ofCassiope lycopodioides D. Don, which has a decussate leaf arrangement, was analyzed using trans- and longisections to generate a three-dimensional viewpoint. The apical dome of this species is relatively high from the middle to the maximal area phase of a plastochron. Therefore, the initial protrusion of a pair of leaf primordia occurs laterally on an apical dome conspicuously in contrast to the cases ofDaphne pseudo-mezereum andClethra barbinervis whose apices are nearly flat or slightly convex. The structure of the apex ofCassiope, however, may be understood with the concept of “apical sectors” on the same basis asDaphne andClethra (Hara, 1961, 1962, 1971a, b, c).     

ARABIDOPSIS THALIANA HOMEOBOX GENE1 establishes the basal boundaries of shoot organs and controls stem growth

Apical meristems play a central role in plant development. Self-renewing cells in the central region of the shoot meristem replenish the cell population in the peripheral region, where organ primordia emerge in a predictable pattern, and in the underlying rib meristem, where new stem tissue is formed. While much is known about how organ primordia are initiated and their lateral boundaries established, development at the interface between the stem and the meristem or the lateral organs is poorly understood. Here, we show that the BELL-type ARABIDOPSIS THALIANA HOMEOBOX GENE1 (ATH1) is required for proper development of the boundary between the stem and both vegetative and reproductive organs and that this role partially overlaps with that of CUP-SHAPED COTYLEDON genes. During the vegetative phase, ATH1 also functions redundantly with light-activated genes to inhibit growth of the region below the shoot meristem. Consistent with a role in inhibiting stem growth, ATH1 is downregulated at the start of inflorescence development and ectopic ATH1 expression prevents growth of the inflorescence stem by reducing cell proliferation. Thus, ATH1 modulates growth at the interface between the stem, meristem, and organ primordia and contributes to the compressed vegetative habit of Arabidopsis thaliana.