plant structure (leaves, stems, roots)
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Plant Structure (Leaves, Stems, Roots) . Honors Biology. Plant Body. Shoot system = leaves + stem Root system Meristem = cells that divide for life of plant, can give rise to all plant structures 3 BASIC Organs Roots Stems Leaves. 2 BASIC Systems BOTH SYSTEMS DEPEND ON THE OTHER - PowerPoint PPT PresentationTRANSCRIPT
Plant Structure (Leaves, Stems, Roots)
Honors Biology
Plant Body• Shoot system = leaves
+ stem• Root system• Meristem = cells that
divide for life of plant, can give rise to all plant structures
3 BASIC Organs– Roots– Stems– Leaves
2 BASIC Systems• BOTH SYSTEMS DEPEND ON THE
OTHER–Root System (roots)
receive sugars and other nutrients from photosynthetic parts– Shoot System (leaves and
stems) depends on water & minerals absorbed from the soil by roots.
Tissue Types in Vascular Plants• Dermal Tissue
– Covers/ protects plant– Makes cuticle on stems/ leaves– Allows for better H2O absorption
(root hairs)– Make guard cells
• Vascular Tissue (xylem & phloem)– Transport and support– Throughout the plant– Called “veins” in leaves– Called the “stele” in stem or root
• Ground Tissue– Between dermal and vascular tissues– Storage– Photosynthesis (makes sugars)– Support
Dermaltissue
Vasculartissue
Groundtissue
Plant Body-LEAF
Functions– Exposes surface to sunlight– Major site of photosynthesis– Conserves water– Provides for gas exchange– Transpiration-water movement throughout the
plant; evaporation of water from plant leaves
Blade
Petiole
Leaf = blade + petiole
Stoma = opening in the leaf for
gas exchange, water evaporation
Leaf Structure-Dermal layers• Cuticle-The thin waxy
covering on the outer surface of the leaf has a thin waxy covering This layer's primary function is to prevent water loss within the leaf. (Plants that live entirely within water do not have a cuticle).
• Directly underneath the cuticle is a layer of cells called the epidermis (upper and lower)
Leaf Tissues• Mesophyll
– Ground tissue between upper and lower epidermis
– Two types:• Palisade parenchyma (mesophyll) cells
– Lots of chloroplasts in these cells– Most photosynthesis occurs here
• Spongy parenchyma (mesophyll) cells– Lots of air spaces where O2 and CO2
circulate– Near stomata (Think: sponges have lots
of air spaces)
• Veins– Xylem and phloem are continuous from
roots through stem to leaves
Vascular Tissue (Veins)• Transports materials in roots, stems,
& leaves.• Xylem (dead cells-water conducting)– Carry water & minerals up from roots– Tube-shaped dead cells
• Their walls are used as water pipes
• Phloem (living cells-food conducting)– Carry nutrients (food) throughout
plant• SUGARS (sucrose), amino acids….
– Tube-shaped living cells
Stomata and Guard Cells• The underside portion of a leaf has stomata and is the site of
transpiration (water loss) and gas exchange.
Stomata help regulate the rate of transpiration
• Guard cells –2 cells on either side of stomata
(surrounds stomata)–regulate water loss
• What conditions will promote closing of guard cells?–Hot, dry, windy conditions
Stoma Opening/Closing
• http://academic.kellogg.edu/herbrandsonc/bio111/animations/0021.swf
Plant Body- ROOTSRoot Functions• Anchors plant in
soil • Takes up water and
minerals from soil
& gymnosperms
Modified Roots• Some plants have modified
roots • Adventitious roots arise
aboveground spread over large areas
• Storage roots hold “food” called root tubers
Plant Body-STEMStem: series of nodes and internodesFunctions• Support for the plant body • Holds leaves up to light• Transports nutrients throughout plant
Xylem conducts waterand minerals
Phloem transports sugar
Division of Meristem Cells Causes Plant Growth
• Apical Meristem– tips of root and
shoot– increase in height
• Lateral Meristem– cylinders within
plant body– increase in width
• Apical meristems are located at the tips of roots and in the buds of shoots– elongate shoots and roots, a process called primary
growth• Lateral meristems
– add thickness ONLY to woody plants, a process called secondary growth
Types of Meristems (like embryonic stem cells)
MONOCOT PLANTS vs. DICOT PLANTS– Monocots: grasses, lilies, orchids, corn, palms, onions– Dicots (aka-Eudicots): broadleaf trees, shrubs, most flowers,
and vegetables.