Biology Olympiad Training Program 2006 1 Biology Olympiad Training Program 2006 2 PLANT STRUCTURE Biology Olympiad Training Program 2006 3 Basic plant organs Roots anchor the plant in the soil, absorb nutrients and water, and store food. Stems support and bear the leaves and buds of the plant. Some green stems can photosynthesise. Leaves are the main photosynthetic organs of most plants. Biology Olympiad Training Program 2006 4 Modified shoots Stolons – asexual reproduction. e.g. strawberries Rhizomes – horizontal underground stems. e.g. grass Tubers – food storage. e.g. potatoes Bulbs – food storage. e.g. onion Biology Olympiad Training Program 2006 5 Modified leaves Tendrils – clinging supports. e.g. peas Spines – self defence. e.g. cacti Succulent – water storage. Bright leaves – attractant. Biology Olympiad Training Program 2006 6 Angiosperms - Monocots and dicots Monocots Dicots Seeds/ Embryos Leaf venation Stems Roots Flowers Biology Olympiad Training Program 2006 7 Plant tissues Dermal – generally single celled layer that covers and protects young plant parts. Vascular – conducting tissue, composed of xylem and phloem. Ground – all tissues found between the dermal and vascular systems. All plant organs are made of 3 tissue types:
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PLANT STRUCTURE Basic plant organsmembers.optusnet.com.au/~romainedb/notes/Lecture 5 grey.pdf · All plant tissues are made of 3 basic cell types: 1. Parenchyma – ‘typical’
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Biology Olympiad Training Program 2006 1
Biology Olympiad Training Program 2006 2
PLANT STRUCTURE
Biology Olympiad Training Program 2006 3
Basic plant organs Roots anchor the plant in the soil, absorb nutrients
and water, and store food.
Stems support and bear the leaves and buds of the plant.
Some green stems can photosynthesise.
Leaves are the main photosynthetic organs of most
plants.
Biology Olympiad Training Program 2006 4
Modified shoots
Stolons – asexual reproduction. e.g. strawberries
Rhizomes – horizontal underground stems. e.g. grass
Tubers – food storage. e.g. potatoes
Bulbs – food storage. e.g. onion Biology Olympiad Training Program 2006 5
Modified leaves
Tendrils – clinging supports. e.g. peas
Spines – self defence. e.g. cacti
Succulent – water storage. Bright leaves – attractant.
Biology Olympiad Training Program 2006 6
Angiosperms - Monocots and dicots
Monocots
Dicots
Seeds/ Embryos
Leaf venation
Stems Roots Flowers
Biology Olympiad Training Program 2006 7
Plant tissues
Dermal – generally single celled layer that covers and protects young plant
parts.
Vascular – conducting tissue, composed of xylem and phloem.
Ground – all tissues found between the dermal and vascular systems.
All plant organs are made of 3 tissue types:
Biology Olympiad Training Program 2006 2
Biology Olympiad Training Program 2006 8
Dermal tissue
Dermal tissue, or the epidermis, is generally a single layer of tightly packed cells.
Functions in:
Protection of young parts of plant. Absorption of water and nutrients (root hairs).
Water retention (secretion of waxy cuticle).
Biology Olympiad Training Program 2006 9
Vascular tissue - xylem Xylem is made of tracheids and vessel elements. They are dead at functional
maturity.
They transport water and dissolved minerals upwards from the roots into
the shoots.
Tracheids are long, thin cells with tapered ends, found mainly in simple
plants
Vessel elements are wider, shorter, thinner walled and less tapered, mainly
in complex plants
Biology Olympiad Training Program 2006 10
Vascular tissue - phloem Phloem is made of sieve-tube
members. They are alive at functional maturity.
It transports sucrose, organic compounds, and some mineral ions
up and down the plant.
One companion cell accompanies each sieve-tube members.
Sieve plates are porous walls between sieve-tube members.
Biology Olympiad Training Program 2006 11
Ground tissue Ground tissue is tissue that is neither dermal nor vascular.
It is more than just filler. It also functions in photosynthesis,
storage, and support.
In dicot stems, ground tissue is divided into the pith, internal to the vascular tissue, and cortex, external to the vascular tissue.
Biology Olympiad Training Program 2006 12
Cell types
All plant tissues are made of 3 basic cell types:
1. Parenchyma – ‘typical’ cells.
2. Collenchyma – growth support.
3. Sclerenchyma – support.
A major difference is in their cell wall structure.
Biology Olympiad Training Program 2006 13
Plant cell review Plants have chloroplasts
(sites of photosynthesis), a central vacuole (storage of
substances) surrounded by the tonoplast, and a cell wall (maintaining cell and plant
shape).
The protoplasm is the part of the cell interior to the cell
wall, i.e. the plasma membrane, the cytoplasm,
and the nucleus.
Biology Olympiad Training Program 2006 3
Biology Olympiad Training Program 2006 14
Parenchyma Parenchyma have thin, flexible primary
walls and no secondary walls.
They are the least specialised of the 3 cell types. Their protoplast typically has a large
vacuole.
Parenchyma perform most of the metabolic functions of the plant – eg
photosynthesis, storage of organic compounds, etc.
Biology Olympiad Training Program 2006 15
Collenchyma Collenchyma have unevenly thickened primary walls, and lack secondary walls.
Mature collenchyma cells are living, flexible, and elongate with the stems and
leaves they support.
They act as support for young parts of the plant shoot, that
are actively growing
Biology Olympiad Training Program 2006 16
Sclerenchyma Sclerenchyma have thick secondary
walls hardened by lignin.
Mature sclerenchyma cells are dead at functional maturity and cannot elongate.
Tracheids and vessel elements (of xylem) are made of sclerenchyma.
Fibers are long, slender, and tapered, and usually occur in groups.
Sclereids are short and irregular in shape.
Biology Olympiad Training Program 2006 17
PLANT GROWTH
Biology Olympiad Training Program 2006 18
Growth and development
Growth – irreversible increase in mass resulting from cell division and cell expansion.
Development – sum of all the changes that progressively elaborate an organism’s body.
Biology Olympiad Training Program 2006 19
Meristems Meristems are tissues that are
perpetually embryonic (i.e. they are totipotent cells)
Apical meristems supply cells for growth in length – primary growth.
Lateral meristems supply cells for growth in girth – secondary growth.