LEAVES
ALTERNATE – leaves unevenly spaced, usually on either side of a twig, with one leaf per node
AUTUMN COLOURS – the chlorophyll decomposes and the leaf loses its green colour, leaving the pigments (red and yellow carotenoids) and anthocyanin in the sap - the nutrients in the leaf withdraw into the body of the tree
AUXINS – hormones that move to dark areas within the stem – they cause the surrounding cells to grow larger and more quickly thus creating a twist in the stem so that a maximum area of the leaf faces the sun
AXIL – junction between leaf stem and twig – usually V shaped
BLADE – also called the lamina – where photosynthesis and transpiration occur – broad usually flat part of the leaf
BRACT – leaf like form at base of leaf or cone scale – often highly coloured
BROADLEAVED – angiosperms (flowering) trees which may be evergreen or deciduous
BUDSCAR – after the bud scales drop a scar is left on the twig
CHLOROPHYLL – chemical in green parts of the tree which aids photosynthesis
CHLOROPLASTS – cells containing chlorophyll, mostly on the upper side of the leaf to obtain most sunlight
CHLOROTIC – lacking in chlorophyll – usually yellow
COMPOUND – leaf divided into leaflets on one stalk
CORDATE – heart shaped
CORIACEOUS – leathery texture
COTYLEDON – leaf or leaves within a seed
DECIDUOUS – shed leaves in autumn
DENTATE – toothed
DICOTYLEDON – two leaves contained within the seed
ENTIRE – leaf edges without indentations
EVERGREEN – retain their leaves through the winter
FASTIGIATE – a conical outline to the canopy
FROND – refers to palm tree leaves
GLABROUS – hairless and scaleless
GLUCOSE – the product of photosythesis used to form cellulose (forms the cell walls) or starch
HELIOTROPISM – the turning of the leaf and stem towards the light
HONEYDEW – a sticky sweet liquid created by aphids taking the sap from leaves (esp. lime) – it falls onto pavements under the trees
INTERNODE – length of twig or branch between the nodes
LEAFLET – small division of a leaf
LEAFSTALK – see petiole
MARGIN – the edge of the leaf, which may be smooth, toothed (dentate), saw toothed (serrations close together), lobed (large rounded teeth) or wavy/undulate
MONOCOTYLEDON – single leaf or leaf pair within the seed
NODE – division of the branch where the leaves grow
OPPOSITE – leaves either side of a twig in pairs
OSMOSIS – the movement of liquid between cells
PALMATE – leaves spread from a single point
PETIOLE – leaf stalk – may be very short or not exist (sessile) – sets the angle of the leaf so that it can receive most sunlight (see AUXINS)
PHOTOSYNTHESIS – the process of fixing carbon dioxide from the air to form glucose and oxygen.
PINNATE – leaves paired in two rows along the stalk, sometimes without a top leaf (terminal leaf) and then called paripinnate - along a central stalk but not paired is called imparipinnate
REVOLUTE – leaf edges turn under
SCALES – tough small leaves, normally produced in the autumn to protect the overwintering buds
SESSILE – leaves with no stalks
SIMPLE – a single leaf blade from one stem
SINUS – the indentation between the lobes
STIPULE – leaflike form at the base of a leaf stalk, often falls off as leaf ages, or maybe formed as a thorn
STOMATA – pores in the outer layer of cells of the leaf, underneath to protect from sunlight
TRANSPIRATION – loss of fluids from the leaf surface by evaporation
VEINS – spread from the petiole across the leaf in various patterns - xylem and phloem cells are found here
WHORLS – 3 leaves or more at the node
A – Needle like leaves – conifers
B – Oblong leaves with nearly parallel sides
C – Lanceolate leaves widest near to the stem
D – Oblanceolate leaves widest at the tip
E - Broad elliptic leaf narrows at tip and stem
F – Broad obovate leaf wide at the tip
G – Broad ovate leaf wide at the stem
H – Heart shape leaf
I – Rounded (orbicular) leaf
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