Botany Terms Starting With D

Deciduous describes plants that lose all their leaves during a particular season each year, such as before winter or during a dry season.

Leaf abscission in deciduous trees is triggered by decreasing day length sensed by phytochrome pigments in leaves, which initiates chlorophyll breakdown, nutrient resorption, and abscission layer formation at the leaf base. Temperate oaks typically drop their leaves over a two- to three-week window in autumn, recycling up to 70 percent of leaf nitrogen back into twigs and branches before abscission. The abscission zone contains a separation layer of small, thin-walled cells and a protective layer that seals the wound after leaf fall, preventing pathogen entry.

Deciduousness is not universal within a species range; some oaks remain semi-evergreen in mild coastal climates, retaining leaves through winter before new growth forces them off in spring.

Dichlamydeous dichlamydeous flower has two distinct outer rings consisting of a calyx made of sepals and a corolla made of petals.

Dichlamydeous flowers contain two distinct whorls of perianth structures: an outer calyx composed of typically green sepals and an inner corolla composed of usually pigmented petals. The calyx protects flower buds during development, while the corolla typically serves to attract pollinators through color and pattern. This two-layered arrangement occurs in families like Rosaceae and Fabaceae and contrasts with apetalous flowers that lack petals or monochlamydeous flowers lacking a distinct corolla.

Dicotyledons, commonly called dicots, are flowering plants whose seeds usually have two seed leaves called cotyledons.

Dicotyledons possess two cotyledons that store nutrients for the developing embryo during germination. Most dicots display reticulate leaf venation with veins forming a net-like pattern, while monocots typically show parallel venation. Dicot stems contain vascular bundles arranged in a ring, and most dicots produce flowers with parts in multiples of four or five rather than three.

The dicot group includes families like Rosaceae, Fabaceae, and Asteraceae, representing roughly 30 percent of flowering plant species.

Dioecious plants have male and female flowers on separate plants; a male plant and a female plant are both needed for seed production.

Dioecious species constitute about 6% of all flowering plant species and have evolved independently across more than 100 plant families. Cannabis sativa and Ginkgo biloba are well-known dioecious species; only female plants produce the psychoactive resin or fleshy seeds, respectively. Dioecy is thought to evolve from hermaphroditism through the accumulation of male-sterility and female-sterility mutations, sometimes on incipient sex chromosomes as seen in Silene latifolia.

Ecological advantages of dioecy include obligate outcrossing, which increases genetic diversity, and sex-specific resource allocation, with female plants typically investing more carbon in fruit and seed production.

Distichous means arranged in two rows; for example, leaves may grow in two lines on opposite sides of a stem.

Distichous arrangement occurs when leaves or other plant parts develop in two distinct vertical rows on opposite sides of a stem axis. This pattern develops through alternating phyllotaxis where successive leaf primordia emerge 180 degrees apart on the apical meristem. The two-ranked arrangement typically creates a flattened shoot profile, allowing more light penetration in dense vegetation.

Grasses, sedges, and many ferns commonly display distichous leaf patterns.

Dormancy is a resting period in which a plant, seed, or bud slows its growth and metabolic activity to survive harsh environmental conditions like extreme cold or drought.

Dormancy is an adaptive suspension of growth and development triggered by environmental cues such as low temperature, photoperiod changes, or drought, with the metabolic rate declining dramatically to conserve stored reserves. Innate dormancy, imposed by the seed or bud itself, may require exposure to cold temperatures or light wavelengths before growth resumes. Imposed dormancy occurs when external conditions such as drought, darkness, or freezing temperatures prevent growth regardless of the seed’s internal state.

Many temperate tree seeds require 4 to 16 weeks of moist cold to break dormancy and germinate in spring, ensuring seedlings emerge when soil temperature and moisture are favorable.

Drupe drupe is a fruit with a soft outer part and a hard stone around the seed; peaches, cherries, and mangoes are drupes.

The drupe is derived from a single carpel and is the defining fruit type of the family Rosaceae, which includes peaches, cherries, plums, and almonds. That stony endocarp, the pit of a cherry or plum, protects, which protects the seed from digestive enzymes and mechanical damage during animal dispersal. Drupe structure follows a consistent three-layer pericarp: the thin exocarp forms the skin, the fleshy mesocarp provides nutrient reward for dispersers, and the stony endocarp encases the seed.

In coconut, the familiar brown shell is the endocarp, the fibrous husk is the mesocarp, and the smooth outer green layer is the exocarp, making it technically a drupe despite its unusual appearance.