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 180^o 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