Glossary - general

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Deciduous – losing all its leaves for part of the year; not evergreen

Declinate – bent or curved downwards or forwards

Decompound – (Cyperaceae) applied to an inflorescence where there are three or more orders of branching

Decumbent – lying on the ground, but with the distal part upright

Decurrent – extending downwards; used of leaf edges when they continue down the stem as wings or raised lines

Decurved – curved downwards and outwards, but not coiled

Decussate – used of opposite organs (i.a. leaves), when alternate pairs are at right angles to each other

Decussate aestivation – the successive pairs of sepals/petals are borne at right angles to each other

Definite – (of shoot growth) in which the axis terminates in an inflorescence; (of cymose inflorescence) in which the axis terminates in a flower

Deflexed – bent abruptly downwards

Defoliate(d) – of which the leaves have been shed

Degraded – less complex, reduced, damaged

Dehiscence – mode of opening (of a fruit capsule or anther)

Dehiscent, dehiscing – splitting; opening spontaneously when ripe, e.g. capsules and anthers

Deltate, deltoid – shaped like an equal-sided triangle (deltoid mainly used of 3-dimensional shapes)

Dendritic – tree-like (e.g. dendritic hairs), branched like a tree

Dendroid – shaped like a tree, with a thick basal part and narrowing branches

Dentate – prominently toothed with acute symmetrical projections (usually of margins)

Dentation – the degree of incision of the margin

Denticidal capsule – dehiscing apically, leaving a ring of teeth

Denticle – small tooth

Denticulate – finely toothed

Depauperate – impoverished; of much lesser stature than normal

Depressed – more or less flattened from above downwards, or at least at the top

Dermal – relating to the epidermis

Dermatogen – the outermost layer of cells (formed from a promeristem), which divide and give rise to the epidermis of the stem, or a mass of tissues, the calyptrogen, in the root; in most angiosperms the root dermatogen (a questioned term) forms the epiblema, the epidermal rootlet cells

Dermatogenic – developing from the outermost layer; from the meristem forming the primordial epidermis

Descending (of ovule or stigma) – turned downwards

Determinate – (1) with finite growth, either ending in an inflorescence or with the growing tip aborting (sympodial); (2) (of inflorescence) main axis ending in a flower, the lateral branches if any following this patterns; centrifugal, basipetal

Dextrorse – towards the right (when viewed from the front), e.g. in climbing stems – Opposite: sinistrorse

Diacytic stomata – the guard cells are covered by two subsidiary cells at right angles to that of stoma; with two subsidiary cells surrounding the guard cells, their radial walls at right angles to the longitudinal axis of the guard cells

Diadelphous – in two bundles (usually of stamens, i.a. in Fabaceae and Polygalaceae)

Diallelocytic stomata – with three subsidiary cells; diacytic stomata with an alternating complex of three or more C-shaped subsidiary cells of graded sizes at right angles to guard cells

Diaphanous – translucent; with light showing through

Diaphragm (of medulla, pith) – septa consisting of sclerified cells which separate the different compartments of the medulla in many plants

Diaphragm – annular structure in the flower of, e.g., Rafflesiaceae, Mitrastemonaceae, and Apodanthaceae.

Diarch root – with four lines of lateral roots; with two xylem strands

Diarch xylem poles – with two xylem poles

Dichasium, dichasial cyme – a peduncle bearing a terminal flower and two bracts, which subtend lateral stalked flowers (simple dichasium); a compound dichasium repeats this branching pattern on the lateral axes

Dichotomous – forked, dividing into two equal branches

Dichotomous venation – with veins branching or forking in pairs equally

Dichotomy – forking, dividing in two

Dicolpate pollen grain – with two colpi

Dicotyledonous type of anther wall formation – only the outer cells in the secondary parietal layers divide periclinally, forming three new layers which differentiate, from outside to inside, into the endothecium, one middle layer and the tapetum; the endothecium and the middle layer are formed from the outer secondary parietal layer, and the tapetum is formed from the inner secondary parietal layer

Dicyclic perianth – see Bicyclic perianth

Didymous – in pairs; divided into two lobes; of anthers, two-lobed with a very short connective

Didynamous stamens – in two pairs of unequal length

Diffuse – loosely spreading

Diffuse parenchyma – axial parenchyma strands scattered randomly within the axial secondary xylem; diffuse parenchyma is hypothesized as the most primitive type of axial parenchyma; single parenchyma strands or pairs of strands irregularly distributed among the fibrous wood elements

Diffuse-in-aggregates parenchyma – axial parenchyma with cells grouped into tangential lines (not more than one cell wide radially); parenchyma strands grouped into short discontinuous tangential or oblique lines

Digitate – like fingers; of a compound leaf, when the leaflets diverge from the same point (palmate)

Dihedral – having two plane faces, or contained by these, as in some seeds

Diheterostylous species – with flowers of two types, pin-eyed and thrum-eyed, respectively, having styles of different lengths and anthers on different levels

Dilated – expanded, widened

Dilation – widening

Dillenioid leaf tooth – with the medial vein ending in a clear expanded apex, the vein often projecting further, not associated with lateral veins

Dimidiate – divided into two parts, but with one part much smaller so only the other one seems present

Dimorphic – with two different shapes or forms

Dimorphic hypoderm cells (of trichoblast) – cells of two different types in the layer of thick-walled supportive or water-storing cells present beneath the epidermis

Dimorphic stem – stem dimorphism; shoots of different architecture, i.a. long shoots and short shoots

Dioecious – with unisexual flowers, male and female flowers on different plants; with male and female plants

Diplobotryoid – a compound (double) closed raceme (with terminal flower)

Diplobotryum – a compound (double) open raceme (without terminal flower)

Diploid – with twice the haploid (somatic) number of chromosomes

Diplostachyoid – a compound (double) closed spike (with terminal flower)

Diplostachyum – a compound (double) open spike (without terminal flower)

Diplostemonous androecium – with the stamens in two whorls, twice as many as the petals, the outer alternate with the inner perianth whorl, the inner alternate with the outer perianth whorl; the outer staminal whorl is initiated before the inner whorl

Diplostemony – see Diplostemonous androecium

Disarticulating – falling apart into its constituent parts (e.g. of a lomentum)

Disc – (1) an enlargement of the floral receptacle or ovary, secreting nectar or displaying stamens, usually ring- or cup-shaped; (2) (Cyperaceae) three-lobed structure occurring at the base of the nutlet in Scleria and Diplacrum

Disc floret – (Asteraceae) the actinomorphic or sometimes bilabiate florets in the centre of the capitulum

Disciform – (Asteraceae) a capitulum with outer filiform florets and inner disc florets

Discoid – (1) like a disc or plate; (2) (Asteraceae) applied to a head with only disc florets (without ray florets)

Discolorous – with two different colours; e.g. the upper surface of a leaf dark green, the lower surface white – Opposite: concolorous

Discrete – separate, individual

Disintegrating – falling apart into its constituent parts

Dispersal – the movement of propagation units such as seeds away from the parent plant by mechanical means, wind, animals etc.

Dispersive protein bodies (of sieve tube cells) – energy dispersive x-ray (EDX) analysis is used in order to investigate the chemical composition of the crystalline bodies of P-protein, e.g. in sieve tube cells; with this approach all elements with atomic number 11 and higher can be detected; some protein bodies are dispersive, whereas others are non-dispersive

Disporangiate (bisporangiate) anther – with two microsporangia

Disporic (bisporic) megagametophyte – developing from two megaspore nuclei from the megaspore tetrad

Dissected – divided into segments

Dissepiment – a partition in an ovary or fruit; septum

Distal – farthest from the place of attachment; opposite to proximal; the distal part of a leaf is its tip

Distichous – arranged in two opposite rows, one on each side of the stem

Distinct – separate from other parts in the same series; free

Disymmetrical – see Bisymmetrical

Dithecal anther – with two thecae

Divaricate – spreading wide

Divergence – gradual separation

Divergent – gradually spreading, but less so than divaricate

Divided – of a structure that is not entire, but split into two or more subunits; i.a. a leaf may be variously divided into lobes or leaflets – Opposite: entire

Dizonosulculate pollen grain – with two sulculi along the equator

Dolabriform – hatchet-shaped

Dolichostylous (of heterstylous flowers) – long-styled – Opposite: brachystylous

Domatia – small pockets, usually present in the lower-surface axils of the leaf veins; acarodomatia

Dormant – not active, awaiting a stimulus to function

Dorsal – synonymous with adaxial or upper in regard to the lamina surface – Opposite: ventral (abaxial)

Dorsal placentation – see Laminar-dorsal placentation

Dorsicide capsule – dehiscing along the dorsal (abaxial) side

Dorsifixed anther – the connective is attached between the base and the apex, i.e. by its back

Dorsiventral – with two surfaces, upper (dorsal) and lower (ventral)

Dorsiventrally – of a solid structure, with a distinct division into lower/abaxial and upper/adaxial surfaces

Dorsobasal – present dorsally yet near the base

Drepanium – a sickle-shaped cyme, the successive flowers springing always from the upper side of their respective axes; a putative monochasial cymose inflorescence, branching not from the adaxial prophyll, but from the leaf above it (and borne at 180o to it), the whole more or less coiled like the tail of a scorpion

Drupaceous – like a drupe; with the character of a drupe, or producing fruit like a drupe

Drupe – a stone fruit (i.a. plum, cherry); a fleshy, single-seeded indehiscent fruit with the seed enclosed in a stony (sclerenchymatous) and often lignified endocarp (pyrene)

Drupelet – in aggregate fruits, the single drupes that, together, form the fruit

Druse – a radiating irregular mass of crystals consisting of a crystalline form of calciumoxalate which is frequently present in cells

Dry type stigma – receptive surface having a hydrated, proteinaceous extracuticular layer or pellicle but no free-flowing secretion; frequent in species with trinucleate (tricellular) pollen grains; the transmitting tissue extracellular matrix (ECM); a freely flowing ECM (Wet type stigma) was ancestral to a cuticle-bound ECM (Dry type stigma); the most recent common ancestor of extant angiosperms produced an ECM that was structurally and functionally equivalent to a Dry type stigma; Dry type stigmas are composed of a cuticle and primary wall containing compounds which facilitate the adhesion and growth of the male gametophyte (including methyl-esterified homogalacturonans, arabinogalactan-proteins, and lipids)

Duplicate – double or folded, twin

Dyad (of pollen grains) – two microspores (pollen grains) fused into a dispersal unit