#algae

• Actinella — Romanian name adapted from the taxonomic genus Actinella. In botany, it defines a genus of herbaceous plants (often associated with Hymenoxys) in the Asteraceae family, or a genus of unicellular algae (diatoms) characterized by asymmetric, arched siliceous shells that expand radially at one extremity. In micropaleontology, these fossilized structures are used as environmental indicators.
• Aerocyst — An anatomical structure in the shape of a bladder, pouch, or sac filled with air, found in the stem or leaf structure of certain aquatic plants and marine algae (such as those of the genus Fucus). This floating vesicle functions as a natural hydrostatic organ, keeping the plant at the water surface to capture a maximum amount of sunlight required for photosynthesis.
• Aeroplanctophytes — Microscopic plant organisms, specifically unicellular algae, aerobic bacteria, or fungal spores, structurally adapted to float and survive passively in the lower and middle layers of the atmosphere. These micro-plants utilize air currents for dispersion and colonization, playing a discrete but important ecological role in global aerobiological ecosystems.
• Agar — A natural gelling substance (polysaccharide) extracted from the cell wall of certain species of red algae (Rhodophyta), utilized as a solid culture medium in microbiology, a thickening agent in the food industry, and a stabilizer in chemistry; in a historical and religious sense, represented as a proper noun, it is the biblical name of Sarah's and Abraham's Egyptian maidservant, mother of Ishmael, considered an ancestral structural figure in Judaic, Christian, and Islamic traditions.
• Agar-agar — A mucilaginous polysaccharide product extracted from the cell wall of certain red marine algae (especially from the genera Gelidium and Gracilaria), commercialized as a powder, flakes, or gelatinous strips insoluble in cold water but soluble in hot water. Structurally, it gels upon cooling to form a rigid, thermally stable three-dimensional network, widely used in microbiology as a support for bacterial cultures, in confectionery as a plant-based substitute for animal gelatin (under code E406), and in pharmaceutical technology.
• Algophilous — Manifesting a distinct structural biological affinity, attraction, or optimal evolutionary adaptation for aquatic environments dominated by algae, stagnant ponds, or laboratory algal cultures; a plant, bacterial, or small animal organism that lives, develops, or feeds in close symbiosis with algae. As a masculine noun, it describes an algae-loving microorganism or microscopic species whose cellular architecture is metabolically optimized to absorb organic nutrients released by phytoplankton in aquatic ecosystems.
• Alga — A lower, cryptogamic thallophyte plant with a body unsegmented into true roots, stems, or leaves, containing chlorophyll and other photosynthetic pigments. It lives primarily in aquatic environments or high-humidity spots. Classified into green, brown, or red variants, it plays a vital role in global ecosystems.
• Algotrophic — Feeding on algae or depending nutritionally on algal biomass; algophagous. In aquatic ecology, the term characterizes secondary consumer organisms or trophic webs within a biotope where primary production is overwhelmingly provided by microscopic or macroscopic algae.
• Anadyomena — A genus of marine green algae in the family Anadyomenaceae, structurally characterized by a flat, foliaceous, fan-shaped or leaf-like thallus made of branched filaments arranged in a distinct single cellular layer. These macroalgal organisms develop primarily in warm tropical and subtropical waters, being studied in systematic algology for their unique flabellate cellular architecture and their role in reef biocenoses.
• Androspore — A specialized asexual male spore (found in certain green algae belonging to the Oedogoniales order) which, upon release and attachment to a female plant, structurally germinates to produce a dwarf male filament, a structure subsequently responsible for producing antherozoids.
• Aulophytes — A group of lower plants (algae, mosses) or parasitic and saprophytic plant organisms that develop inside hollow cavities, cellular channels, natural tubes, or tissues of other host plants, without necessarily causing immediate structural degradation.
• Autospore — A type of non-motile, asexual spore produced within the parental cell wall in certain species of unicellular green algae (such as the genus Chlorella). The autospore is a perfect, fully formed microscopic replica of the mother cell, possessing the same cellular framework and its own membrane before being released via the rupture of the outer protective wall.
• Diatoms — A class of microscopic unicellular or colonial algae, scientifically known as Bacillariophyceae or commonly as diatoms, characterized by a silicified, rigid, and ornamented cell wall called a frustule, consisting of two overlapping valves like a box. These aquatic photosynthetic organisms play a fundamental ecological role as primary producers in the phytoplankton of seas and fresh waters, with their fossil accumulations forming diatomite.