Leaf Teeth Research Articles

Androecial development and systematics inFlacourtiaceae s. l.

Androecial development of 13 species belonging to six tribes ofFlacourtiaceae has been investigated. While inScolopieae andFlacourtieae the stamens develop centrifugally, inErythrospermeae, Oncobeae andPangieae they are initiated in a centripetal sequence or a sequence that is neither distinctly centripetal nor centrifugal. The distribution of these developmental patterns coincides with the distribution of other characters (e.g. cyanogenic compounds, salicoid leaf teeth) and therefore supports a split of the family intoFlacourtiaceae s. str. (containing theScolopieae, Homalieae, Prockieae, Flacourtieae, Casearieae andBembicieae) andKiggelariaceae (withErythrospermeae, Oncobeae andPangieae) and is in accordance with results of recentrbcL studies.

Taxonomic continuum of Alchemilla (Rosaceae) in Estonia

23 widespread apomictic Alchemilla microspecies occurring in Estonia are analyzed to investigate whether the species and higher rank taxa are distinct, how variable these taxa are and which characters distinguish them better. Cluster analysis, discriminant analysis, analysis of variance, principal component analysis and continuum analysis are used for data processing. The characters form four correlative groups, describing (i) vegetative and (ii) generative parts of the plant body, (iii) hairiness characters and, (iv) leaf teeth measurements. The best characters according to analysis of variance for disünguishing species are hairiness characters, but often they distinguish only few species very clearly and cannot be used for the remaining ones. Hence the other characters cannot be excluded. From the studied species only A. plicata, A. semilunaris and A. lindbergiana are significantly distinct from all others. The remaining ones form a complicated network of mutually indistinct pairs. Higher rank taxa — sections and series according to Rothmaler, Fröhner and Yuzepchuk are better separated, containing very few mutually indistinct pairs. Results from species centroids' clustering are most congruent with Fröhner's system, but still some changes seem to be necessary and a corrected system is proposed here. Section Plicatae is split into two series: Pubescentes and Barbulatae, sections Alchemilla, Ultravulgares and Decumbentes are joined as three series of section Hirsutae, and A. filicaulis is moved from section Plicatae to section Coriaceae. Coriaceae should also be split into three series: Exuentes (A. filicaulis), Glabricaules (A. glabricaulis) and Coriaceae (other species).

THE ECOLOGICAL SIGNIFICANCE OF LOBED AND TOOTHED LEAVES IN TEMPERATE FOREST TREES

Leaves with toothed and lobed margins are frequent in deciduous forests but are rare in moist tropical forests. We hypothesize that leaf teeth may be important to deciduous species as sites of precocious, early season photosynthesis. To test this hypothesis we dosed leaves with 14CO2 and used autoradiography to examine the spatial distribution of photosynthesis within immature leaves of 18 woody species of North Carolina Piedmont forests. We found a significant concentration of early season photosynthesis on the margins of eight species with prominent teeth or lobes, but not in seven toothed or lobed leaf species and in none of the four entire-leaf species.

RAPD mapping of three QTLs determining trichome formation in Microseris hybrid H27 (Asteraceae:Lactuceae)

Segregation for 289 random amplified polymorphic DNA markers (RAPDs) has been determined in 106 F2 plants of an interspecific hybrid (H27) between Microseris douglasii (strain B14) and M. bigelovii (C94). Multicelluar trichomes ("type D", specific for Microseris) occur on the leaf teeth of early vegetative rosettes of the B14 parent and on the leaf blades of later rosettes in both parents. Trichomes on the leaf blades appear earlier and eventually more densely in B14. Segregation for trichome appearance is quantitative and strongly transgressive in the F2 hybrid. Cosegregation between RAPDs and trichome phenotypes combined with linkage data have revealed a main gene ("quantitative trait locus A", QTL-A) with a pleiotropic effect on all trichome characters and two unlinked additive modifiers (QTL-B, QTL-C). Alleles of both modifiers reduce the main gene effect in each parent. Their recombination explains the occurrence of plants with transgressive phenotypes in the hybrid offspring. Additional QTLs affecting trichomes are at and below the level of statistical significance.

Hydrodynamic Modelling Study of Angiosperm Leaf Venation Types

AbstractThe morphology of leaf venation has been studied repeatedly and various systems have been proposed for the classification of the observed leaf venation patterns. Almost nothing is known, however, about the functional properties of the various venation types. Using a computer modelling approach we analysed the water transport properties of typical craspedodromous and brochidodromous venation patterns. The water transport through the leaf and the veins was modelled as a fluid flow through a porous medium and the mathematical model was solved with the Finite Element Method. The simulations illustrate that the leaf margin represents a critical region in terms of water supply. The results provide a plausible functional explanation for three well known phenomena: 1) the correlation between craspedodromous venation and the formation of leaf teeth; 2) the fact that craspedodromous venation is more common in temperate than in tropical regions and 3) the fact that xeromorphic leaves tend to have more closed venation.

Leaf teeth, transpiration and the retrieval of apoplastic solutes in balsam poplar

The rapid flow of the transpiration stream through major veins to leaf teeth was followed in leaves of Populus balsamifera L., using the tracer sulphorhodamine G (SR), which probes for cells with H+‐extrusion pumps. The tracer accumulated quickly in the hydathodes of the teeth. It was shown by freeze‐substitution and anhydrous processing that SR was taken up by phloem parenchyma and epithem cells of the hydathode. When 14C‐labelled aspartate was fed to the leaves in the transpiration stream, it also was taken up most strongly by the same phloem parenchyma and epithem cells. It is proposed that one function of the hydathodes in leaf teeth is the retrieval of solutes from the transpiration stream.

Another arborescent umbellifer: a new species of Steganotaenia from north-east tropical Africa

THULIN, M., 1991. Another arborescent umbellifer: a new species of Steganotaenia from north-east tropica] Africa. The new species Steganotaenia commiphoroides is described from central and southern Somalia, and south-eastern Ethiopia. It differs from the likewise arborescent S. araliacea, widespread in tropical Africa, in, for example, its 3-foliolate or occasionally simple leaves, leaf teeth with shorter aristae, shorter petioles and pedicels, and fruits with a pair of distinctly winged dorsal ridges.

Leaf teeth, transpiration and the retrieval of apoplastic solutes in balsam poplar

Leaf teeth, transpiration and the retrieval of apoplastic solutes in balsam poplar

Comparison of Hydathode Structure in Micropropagated Plantlets and Greenhouse-grown ‘Queen Elizabeth’ Rose Plants

Abstract Foliar anatomical comparisons were made between in vitro-grown plantlets and greenhouse-grown plants of ‘Queen Elizabeth’ rose (Rosa sp.) using scanning and light microscopy. Each acuminate leaf apex and marginal serration had a terminal hydathode region composed of a glandular tip and a subterminal, adaxial group of sunken water pores. Leaf apices of greenhouse-grown plants had up to 35 water pores per hydathode, while cultured plantlets had < 20. Hydathodes of leaf serrations had up to 10 water pores in both sample groups. Water pores and stomata of plantlet leaves were open, while those of greenhouse-grown plants had smaller apertures or were completely closed. Internally, hydathodes were delimited by a bundle sheath extending below the vascular tissues and approaching the adaxial epidermis on each side of the water pore zone. Files of tracheary elements extended various distances into the leaf teeth. Small, irregularly shaped parenchyma cells (epithem) abutted on the xylem parenchyma cells, filling the space between the files of tracheary elements and the adaxial epidermis. The hydathodes of plantlet leaves were smaller with fewer water pores and reduced epithem than those of greenhouse-grown plants. Ex vitro guttation probably occurs as a result of increased water potential and high relative humidity when plantlets are transferred from culture to soil.

Hydathode Structure of Micropropagated Plantlets and Greenhouse-grown ‘Totem’ Strawberry Plants

Abstract Leaves of in vitro-grown plantlets and greenhouse-grown plants of ‘Totem’ strawberry (Fragaria × ananassa Duch.) were compared using scanning and light microscopy. Each apex and marginal serration of in vitro- and greenhouse-grown leaves had a terminal hydathode region. The leaf teeth were composed of an acuminate-mucronate tip, obscured in greenhouse-grown plants by an abaxial cluster of thick-walled unicellular trichomes, and a subterminal, adaxial group of sunken water pores. Water pores and stomata of plantlet leaves were open, whereas greenhouse-grown plant leaves had closed water pores and stomata or comparatively small apertures. Internally, the hydathodes of greenhouse-grown plants and cultured plantlets were delimited by a bundle sheath that extended below the vascular tissues, approaching the adaxial epidermis on each side of the zone of water pores. Between the epidermis and the vascular tissues were loosely arranged epithem cells. The hydathodes of plantlet leaves were smaller than greenhouse-grown plants, with fewer water pores and reduced epithem.

Hydathode anatomy in Potentilla palustris (Rosaceae)

Guttating leaf teeth of Potentilla palustris plants from Wisconsin, USA, were cleared or processed for plastic sectioning or scanning electron microscopy. Anatomical features include: 1) long slender hydathode area occupying most of the tooth, 2) adaxial pad of small, flat epidermal cells with 50 or more sunken water pores about the size of ordinary abaxial stomates, 3) three converged bundles that extend distally, where their tracheary files are separated by intervening files of xylem parenchyma cells with sinuous walls, 4) adaxial mass of small, loosely arranged epithem cells above the xylem, 5) one slender phloem strand that extends only about a third of the way into the hydathode, and 6) bundle sheath extending distally only abaxially and along the flanks of the hydathode. Potentilla hydathodes differ significantly from non‐guttating ones described earlier in Physocarpus (Rosaceae).

Distribution and Anatomy of Hydathodes in Asteraceae

Hydathodes have been reported as rare for the Asteraceae, but we collated published reports of guttation, water pores, and hydrathodes from ca. 80 genera of 10 tribes. Only a few incomplete anatomical descriptions were found. Leaf teeth with guttation droplets were removed for anatomical study from Ambrosia trifida, Arctium minus, Erigeron annuus, Eupatorium rugosum, Lactuca scariola, Rudbeckia laciniata, and Silphium perfoliatum. Conspicuous xylem, but very little phloem, enters each tooth. Phloem ends well before xylem termination. Xylem diverges distally into individual files of tracheary elements separated by parenchyma. Progressively toward the tooth apex, xylem parenchyma proliferates, and successive cells are at first more elongate with increasingly sinuous walls, then shorter, broader, and lobed. The epithem beyond xylem termination resembles ordinary mesophyll chlorenchyma. The bundle sheath is variably developed but always incomplete. Water pores resemble ordinary stomata but are mostly sunken, ...

Morphology, Anatomy, and Relationship of Extrafloral Nectaries and Hydathodes in Two Species of Impatiens (Balsaminaceae)

We studied nectaries and hydathodes in Impatiens scabrida and I. balfourii (Balsaminaceae), two Himalayan natives In I balfourii a pair of equal, ovoid nectaries occurs in the stipular position at each node; in I. scabrida a shelflike nectary occurs in the stipular position on one side of the petiole base, with poorly developed nectary tissue on the other side A core of small, isodiametric, closely packed cells and large raphide-bearing idioblasts occupies the central portion of each nectary. In both species, the foliar nectaries on the proximal three or four pairs of leaf teeth are round to elongate and are similar internally to the larger nectaries. Both types are vascularized to some extent, primarily with phloem Hydathodes occur on all leaf teeth distal to those bearing nectaries; they are vascularized with xylem elements that terminate about the midpoint of the tooth beneath an area of open stomata on the adaxial surface Structures intermediate between nectaries and hydathodes are present in I balfourii but not in I. scabrida We postulate an origin of these Impatiens nectaries from hydathodes. Nectar was analyzed using gas chromatography. Floral nectar from both species contains nearly equal concentrations of fructose, glucose, and sucrose. The stipular nectar of I scabrida is glucose dominant