plants

• plants belong to the kingdom plantae
• they are multicelled organisms capable of making their own food (autotrophic)
• flowering plants are divided into two groups - monocotyledons and decotyledons
• a cotyledon is an embryonic seed leaf
• the cotyledon is a food store in seeds
• monocots have one cotyledon in their seeds eg. grass
• dicots have two cotyledons in their seeds eg. carrots and ash tree
• dermal tissue - forms the outer protective layer in plants
• groud tissue - makes up majority of the plant and have many functions depending on its location including photosynthesis, support and storage
• vasucular tissues - a transport tissue made up of xylem and phloem
• xylem transports water and dissolve minerals from the roots up through the plant
• phloem transports food around the plant from where its produced to where it is needed
• meristematic tissue is found in root and shoot tips and in all buds and develops into each of the other 3 tissue types in plants
• a meristem is composed of unspecialised cells that are continuously dividing by mitosis
• plants only grow at their tips - happens at apical meristems
• functions of the shoot system - photosynthesis, storage, transport and support
• functions of roots - anchors the plant in the soil and stores food
• tap roots consist of a main root called a tap root - lateral roots grow from the main root - the tips of the lateral roots have thousands of tiny root hairs - most dicotyledons have tap roots
• fibrous roots consist of many roots all the same size - most monocots have a fibrous root system
• adventitous roots are roots that are sometimes said to grow in strange places - examples include roots at the base of onions and the gripping roots of ivy
• zone of protection - the root cap protects the root tip as it grows through the soil
• zone of elongation - when new cells formed by the meristem they are very small
• the shoot system is the part of the plant above the ground - it consists of the stem, leaves, flowers and seeds
• functions of stems - to support the aerial parts of the plant, to store food and to transport materials between the leaves and roots
• in monocots the vacualr bundles are scattered at random
• in dicots the vascular bundles are arranged in a ring (xylem always towards the inside)
• tissue at the centre of the stem is called pith - cortex is to the outside
• functions of leaves - to carry out photosynthesis, to allow water to pass out and to store food
• leaves are attached to stem at a node - the stalk of the leaf ic called the petiole
• some leaves do not have a petiole - they are joined directly to the stem - these leaves are said to be sessile
• the pattern of veins on a leaf is called venation - veins contain the vascular tissue
• parallel venation - veins run alongside each other - mostly found in monocots
• net (reticulate) venation- veins form a branching network - mostly found in dicots
• xylem - two types - vessels and tracheids - the living part dies before they reach maturity is xylem is a dead tissue
• xylem tracheids - insides are hollow - the walls of xylem are strengthened by lignin - they are more primitive than vessels
• vessels - have pits in their side walls to allow water to pass from one vessel to another - more efficient at transporting water than tracheids - most commonly found in flowering plants - spiral lignin found in vessels for strength and support
• function of xylem is to transport water and minerals from the roots to the leaves and also gives mechanical support to the plant
• xylem is found in roots, stems, leaves and flowers - usually found in vascular bundles
• phloem is made up of companion cells and sieve rubes
• sieve tubes are long tubular structures - form when cells called sieve tubes join end to end