Plants, Nutrients and Australian Soils

Abaxial

bottom, or back, of the leaf.

Accessory pigments

pigments other than chlorophyll a that absorb light but are not directly involved in photochemical reactions. Generally absorb light in different part of the spectrum from chlorophyll.

Adaxial

upper surface, or "top", of the leaf. The side of the leaf that faces the stem.

Aerobic

having oxygen; oxygenated.

Anaerobic

without oxygen.

Anatomy

structure; or the study thereof. In plants, with an emphasis on tissues and their component cells in the interior of the plant body.

Aquatic

with water as the normal habitat.

Aqueous

of water

Awn

a bristle-like structure, often associated with the flowers of grasses.

Benthic

sea or lake floor. E.g. benthic algae are attached to the sea floor, below the water line.

Bioclimate

Climate suitable for a particular organism. Includes elevation, soil type, temperature, precipitation, aspect (north, south) and so on.

Bladder

a bag or vesicle of some kind. E.g. urinary bladder is a sac that stores urine; inflated vesicles of sea weeds.

Brackish

freshwater which is contaminated with salt water, but generally still drinkable.

Capricious

irregular, unpredictable, inconstant.

Cladode

a specialised stem structure resembling and performing the functions of the leaf. A cladode may be distinguished from a leaf by the presence of buds on its surface.

Community

any group of organisms comprising a number of different species that co-occur in the same habitat or area and interact with each other.

Cone

1. strictly refers to cones of conifers which are well defined groups of specialised spore-bearing structures (sporophylls) arranged around a central axis. 2. Cone-like structures of some angiosperms e.g. aggregate fruits of casurinas and alders.

Dehiscent

the splitting open along predetermined lines of certain plant organs such as anthers, spore capsules and fruits to release their contents. It is often caused by the gradual drying out of the enclosing walls.

Desiccate

to dry out

Deuterium

an isotope of hydrogen, consisting of 1 proton, one electron and a neutron, not present in hydrogen.

Dioecious

plants in which the female and male reproductive organs are separated on different individuls.

Discontinuous

not continous; disjunct.

Diurnal

relative to the alternation of daylight and darkness.

Dorsiventral

having distinct upper and lower sides (dorsal and ventral). E.g. a dorsiventral leaf usually only has palisade mesophyll on the upper side.

Endemic

plant species that grows in a specific area and has a restricted distribution.

Ephemeral

Living for only a short period of time. For example, desert ephemerals complete their life cycle when water is available which may or may not be related to the season.

Eukaryote

cells with a distinct nucleus and often with other well defined organelles as well. (cf. prokaryote.)

Extirpation

the local extinction of a species

Follicle

a dry dehiscent many seeded fruit derived from one carpel. On ripening the follicle splits down on only one side to expose the seeds. E.g. Proteaceae.

Gondwana

the southern supercontinent formed by the break up of Pangea in the Mesozoic, approx 150 million years ago, comprising the present South America, Africa, Arabia, Australia, Antarctica, India and New Zealand.

Grana

region of the chloroplast consisting of layers of membranes (thylakoids). Main site of light reactions of photosynthesis.

Heathlands

vegetation characterised by small leaved shrubs (woody plants) less than 2 m tall. Usually dominated by Myrtaceae (Australia) and Ericaceae (northern hemisphere).

Heterozygous

having two different alleles at a locus in a chromosome pair. e.g. Aa. Heterozygosity is where a substantial proportion of each gene in a given population is represented by more than one allele.

Holdfast

an attachment to a substratum. For example, algae often attach to the substrate with a holdfast.

Honeydew

a liquid high in carbohydrate secreted in small droplets by various insects.

Huxley

Several members of the Huxley family have been famous scientists. Thomas was a key proponent of the theory of natural selection; Julian consolidated the modern synthesis of evolution in the 1920s; Auldus wrote the science fiction classics "Brave New World" and "Island".

Indigenous

belonging naturally to an region.

Intertidal

the zone between the average high and low tide marks.

Inundate

to cover with water

Isobilateral

having the same structure on either side e.g. adult leaves of eucalypts have same tissue arrangement below their dorsal and ventral surfaces.

Kranz anatomy

Structure of a leaf where there is a distinctive sheath of cells around the vascular bundles, observed as a ring in cross section. From the German Kranz meaning ring.

Lignin

a complex carbohydrate polymer making up about 25% of the wood of trees. Also found in the cell walls of sclerenchyma, vessels, fibres and tracheids at maturity. Its distribution in tissues can be shown by staining with specific stains, such as Toluidine Blue.

Lobe

a roundish part which stands out, as of an organ such as a leaf.

Manna

the sugary liquid that flows from wounded eucalypts.

Marine

pertaining to the sea.

Mesophyll

1. a leaf that cannot withstand severe drought. Often soft and dorsiventral in structure. 2. the middle tissue of a leaf, i.e., the soft tissue between the upper and lower layers of epidermis. 3. in the classification of Australian rainforests, used to describe forests dominated by plants with leaves >12.5 cm long.

Mesophyt

a plant without adaptations to environmental extremes often displaying soft, dorsi-ventral leaves (mesophylls).

Monocotyledon

Subclass Monocotyledonae. Contains all flowering plants having embryos with one cotyledon. Members only very rarely possess a cambium and hence lack secondary growth. Leaves generally narrow with parallel veins; floral parts in threes or multiples of three.

Morphology

the study of form, particularly external structure.

Mucilage

A type of gum or slimy substance. From the Latin, mucos or mucus.

Nauplius

earliest larval stage of crustaceans; typically with three pairs of functional limbs, lacking compouind eyes, but usually with a simple median eye.

Neap

Tide of lowest tidal range. Occurs when the gravitational attraction of the sun and the moon act at right angles to each other with respect to the earth ie at the time of first and third quarters of the moon.

Node

the point on the stem where leaves are attached. The area between nodes is called the internode.

Operculum

a cap-like covering that seals an opening. e.g. - calcaeous lid of Galeolaria tubes. - cap-like covering on eucalypt buds

Pangea

the single super continent formed about 240 million years ago comprising the present continental land masses joined together that began to break up 150 million years ago.

Photorespiration

Light-driven reactions which consume oxygen and release carbon dioxide, consuming energy. Catalysed by the enzyme ribulose bisphosphate carboxylase and competes with part of the fixation of carbon dioxide in the Calvin cycle in photosynthesis.

Phyllode

more or less flattened petiole resembling and performing the functions of a leaf. Phyllodes may be seen in a number of species of Acacia. They can be distinguished from leaves by the angle at which they emerge from the stem (they are rotated 90°).

Pneumatophore

specialised aerial roots through which gaseous exchange can take place; found in mangroves and other plants in waterlogged or compacted soils. (Such soils tend to be anaerobic.)

Prokaryote

cells without a distinct nucleus and usually lacking other organelles as well. e.g. bacteria, cyanobacteria (blue-green algae).

Sclerophyll

hard leaved i.e. leaves with rough and pliable texture and evergreen, usually with an abundance of sclerenchyma.

Sclerophyte

plant displaying sclerophyllous features.

Spring tide

Extreme tides of maximum range. Occur at the time of new and full moon, when the sun and moon are in line, either in conjunction or in opposition, with respect to the earth; ie when the gravitational attraction of the sun and moon act together.

Stipe

a supporting structure or stalk.

Stoma

from stoma, meaning mouth. Stomata (plural). Opening in the surface of leaf, and sometimes stem. Usually refers to both the opening and the subtending guard cells.

Stroma

non-membranous part of a chloroplast; ie, not the grana. Site of carbon fixation in photosynthesis (Calvin cycle).

Sublittoral

below the littoral. Roughly corresponds to subtidal.

Subtidal

zone below the average low tide mark

Taxonomic group

group of organisms based on evolutionary relationships.

Taxonomy

theory and practice of describing, naming and classifying organimsms.

Thallus

a vegetative body undifferentiated into root and shoot. Plural: thalli

Thylakoid

membranes shaped liked flattened cylinders, sometimes called cisternae, that run through the chloroplast. Where they are stacked together they are referred to as the grana.

Tidal range

the difference in height between consecutive high and low waters.

Tidal

e.g. tidal mudflats. Area that is covered by tides, frequently or occassionally.

Tide

the periodic rise and fall of the ocean, produced by gravitational effects of the moon and sun on the Earth.

Vagary

This word has a range of meanings including: irregular, inconsistent, unpredictable, capricious, whimsical. Generally used to imply the unpredictable, variable and patchy nature of the environment, especially fires.

Vegetative

the non-reproductive part of a plant or thallus; vegetative reproductionis the production of new individuals from the parts of the plant other than the reproductive organs.

Vesicle

small bladder, cell, bubble or hollow structure.

Xerophyte

plant which can avoid or tolerate drought. Includes sclerophyllous plants, succulents and ephemerals.