Plant Structure
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Transcript of Plant Structure
Plant Structure
Hierarchy of a Plant BodyExtreme developmental
plasticity in plantsStructurally change
morphology, external form, to better suit environmentGenetic factors play small
role tooMore variety within plant
species than animal speciesPlants have organs that
are composed of tissues that are made of cells
Basic organs are roots, stems, and leaves
Cabomba caroliniana, a fanwort
Hierarchy of a Plant BodyPlants aquires resources
from 2 different environmentsCO2 and light from above
groundWater and nutrients from soil
Plants have organs that are composed of tissues that are made of cells to facilitateBasic organs are roots,
stems, and leavesForm root system and
stem systemSystems rely on each other
for materials
RootsAn organ that anchors, absorbs, and store3 types
Taproot system has 1 main vertical root that produces small lateral, or branched, rootsMost eudicots and gymnosperms; i.e. carrots and beetsStore sugars and starches for flowering; why root crops harvested before
floweringAdventitious roots arise from stems or leaves, with each forming
separate lateral rootsCan be modified to provide more support of anchorage; fig. 35.4
Fibrous roots form a mat of thin roots that don’t penetrate deeplySeedless vascular plants and most monocots; i.e. grasses
Root hairs found near the tips aid in absorption and increase SAShort lived and constantly replaced, not to be confused with lateral
roots
StemsAlternating nodes where leaves attach and
internodes, the segments in betweenUpper angle of each leaf contains an axillary bud
which can form a lateral shoot, but are normally dormant
Near the shoot tips are apical buds which inhibit axillary bud growth via apical dominanceConcentration of resources so plant can grow tallerIf apical bud is gone then axillary buds can develop
into lateral shoots and become their own apical budReason for pruning bushes and trimming house plants
LeavesMain photosynthetic part of the plantConsist of a flattened blade and a petiole or
stalk to join to stem at nodeVeins, the vascular tissue, differ in arrangement
between eudicots and monocotsMonocots with parallel veinsEudicots with branched veins
Angiosperms classified by vein branching (floral morphology too)Simple have single undivided bladesCompound blades of multiple leaflets (apical at base of
blade only)
Adaptations for support, reproduction, or storage
Leave Patterns and Deviations
Tissue SystemsDermal tissue system is the outer protective covering
Nonwoody plants have an have an single layer of epidermis that covers and protects young parts of a plantSecretes a waxy cuticle covering to help retain water
Woody plants have a periderm to protect older regions of plant
Vascular tissue system runs throughout the plantXylem transports water and minerals upPhloem transports food down to where its neededCollectively know as stele
Angiosperms have solid central vascular cylinder, leaves and stems have vascular bundles, separate strands of vascular tissue
Ground tissue systemInternal to vascular is called pith, external is cortex
Plant Cell TypesParenchyma cells: thin and flexible primary walls, lack
secondary‘Typical’ plant cells because they are least specializedPerform most of the cell’s metabolic functionsCan regenerate a whole plant from one cell
Collenchyma cells: thicker primary walls, but unevenly thickenedGrouped as strands or cylinders to support young parts of shootsi.e. strings of celeryNo secondary walls or lignin
Sclerenchyma cells: thick secondary walls strengthened by ligninCan’t elongate and reside in parts of plants no longer growingMost dead at maturity, but produce the secondary cell wall before for
supportFibers are long and slender; hemp fibers to make rope and flax fibers wove
into linenSclereids irregular in shape and are shorter; impart hardness to nutshells and
seed coatsXylemPhloem