structure of flowering plants - rochfordbiology.weebly.com
TRANSCRIPT
In this topic:
• Tissue in flowering plants
• Structure of a flowering plant
• Monocotyledons and dicotyledons
Tissue in Flowering Plants
• Also known as ‘meristem’
• Found in:
– Shoot tips
– Root tips
– Buds
Meristematic tissue: Unspecialised cells that are continuously dividing by mitosis
Tissue in Flowering Plants
Tissue Location Function
Dermal tissue Outer covering • Protection
Ground tissue Between dermal and vascular tissues
• Photosynthesis • Storage of food and
wastes • Strength • Support
Vascular tissue • Xylem: transport water & minerals • Phloem: transport food
Vascular Tissue: Xylem
• It is a dead tissue
• Cells lose their cytoplasm early in development and become hollow
• Transports water and dissolved minerals
• Two types of xylem:
1. Vessels
2. Tracheids
Vascular Tissue: Xylem
• Cells join to make a continuous, hollow tube
• Pits in walls let water pass from one vessel to another
• Lignin in walls make them strong
• More efficient than tracheids
• Found in most flowering plants
1. Xylem Vessels
Vascular Tissue: Xylem
• Long, sloping or tapering cells
• Hollow inside
• They overlap and allow water to pass from tracheid to tracheid via pits
• More basic than vessels
• Found in coniferous trees
2. Xylem Tracheids
Vascular Tissue: Phloem
• Transports food
• Mainly made of two elements:
1. Sieve Tubes
2. Companion Cells
• Companion cells are alive so phloem is a living tissue
Vascular Tissue: Phloem
• Long and tubular, with end walls
• End walls have pores to allow passage of materials
• End walls = sieve plates
• Have cytoplasm but no nuclei
• Walls made of cellulose
• No lignin
1. Sieve Tubes
Vascular Tissue: Phloem
• Each sieve tube has an accompanying companion cell
• Each has a nucleus and dense cytoplasm
• They maintain the sieve tube cells
2. Companion Cells
Differences between Xylem and Phloem
Xylem Phloem
Carries water and minerals Carries food
Dead Living
Has lignin No lignin
No companion cells Companion cells
Root Functions
• Anchor & support plant
• Take in water & minerals from soil
• Transport water and minerals
• Some store food in roots.
– Carrots
– Beetroot
– Radishes
• Plumule: will form the shoot
• Radicle: will form the roots
Remember from the Junior Cert:
Broad bean seed
Root Types 3 main types of root
1. Tap roots • Main root develops from the radicle • Also called the primary root • Many smaller roots grow from the tap root • Found in most dicotyledons Dandelion Carrot
Root Types
2. Fibrous roots
• Radicle withers and dies • A group of equally sized roots left behind • These emerge from the base of the stem • Found in monocotyledons Grasses Marigold
Root Types
3. Adventitious roots
• Related to fibrous roots • Grow from unusual places on a plant • Can come from anywhere on a stem or branches,
depending on the plant • Examples: Ivy Banyan tree
Root structure • All roots have the same general structure
Zone Function
Zone of protection A root cap protects meristematic tissue as it pushes through soil
Meristematic zone Meristem that undergoes rapid mitosis for root growth
Zone of elongation Newly produced cells increase in size
Zone of differentiation
Cells specialise into a specific plant tissue type
Stem functions
• Support leaves & flowers
• Transport:
– water & minerals from roots to leaves
– food from leaves to roots
• If green: photosynthesis
• Some store food.
– Potato
– Asparagus
Stem Structure
Nodes: points on the stem where new branches and leaves develop
Internodes: regions between nodes where no branching occurs
Stem Structure
Part Location Function Apical Bud
(or terminal bud) Tip of the stem
Causes the stem tip to grow
Axillary bud (or lateral bud)
Between a leaf and stem
Produce new branches or flowers
Leaf functions
• Photosynthesis
• Gas exchange
• Transpiration
• Some store food.
– Cabbage
– Spinach
Leaf Structure
• Petiole = stalk of the leaf
• Leaves without a petiole are known as sessile
Long petioles in rhubarb Sessile leaves on speedwell
Leaf Structure
• Leaf veins are xylem and phloem vessels
• Xylem is always on the top side of the leaf
• Phloem is always below the xylem
Leaf Venation
• Veins run in parallel • Found in most monocots
Grasses Daffodils
Parallel Venation
• Veins form a branching network
• Found in dicots Rose Horse chestnut
Net/Reticulate Venation
Monocotyledons
• Often referred to as ‘Monocots’
• Examples:
Cotyledon: the first leaf that develops in a seed
Daffodils Grasses Cereals Tulips