Transcript Plant Structure and Growth

Plant Structure, Growth, and
Development
Introduction
The Angiosperm Body
Plant Growth
Introduction to Modern Plant
Biology
• Molecular biology is identifying crucial
genes (flower development); giving a better
understanding of processes such as water
flow, disease resistance, shoot and root
control
• Structure and function is a key theme
The Angiosperm Body
• Problems to be solved: gravity, light, water
transport, reproduction, and desiccation
• Root and shoot systems
The Root System
• Functions: anchor, store food, absorb and
conduct water and minerals
• two types: taproot and fibrous root systems
• role of root hairs
• mycorrhizae
• adventitious roots: form above ground from
stem or leaf
The Shoot System
• Stems, leaves and flowers
• growth occurs at apex
• apical dominance has evolutionary
importance
• underground stems:bulbs and
rhizomes(potatoes)-store food
• leaves: main photosynthetic organ
Types of Plant Cells
• Function determined by protoplast and cell wall
adaptations
• five types of plant cells:
1. Parenchyma-synthesis and storage
2. Collenchyma-support in young plants
3. Sclernchyma-thick secondary walls, lack
protoplast in mature cells?, supportive
4. Xylem-water conduction, two types:
tracheids and vessel elements
5. Phloem-food conduction
Tissue Systems
• Three tissue systems: dermal, vascular and
ground tissues
• Dermal-single outside layer
• Vascular-xylem and phloem, transport and
support
• Ground-between dermal and vascular,
storage, synthesis, and support
Plant Growth
• Meristems generate cells; two types: apical
and lateral
• genetically determined life spans (most)
• annuals and perennials
• plants exhibit indeterminate growth
• two types of growth: primary and secondary
Root Growth
• Primary growth divided into three zones:
1. Cell division: apical meristem, this
differentiates into: protoderm, procambium,
and ground meristem (primary tissues)
2. Cell elongation: elongate at least 10X,
pushes tip through the soil
3. Maturation: cells complete their
differentiation
Primary Tissues in the Root
• Protoderm: outermost layer of primary meristem,
give rise to epidermis, many with root hairs
• Procambium: forms stele (central cylinder)
containing xylem and phloem,
• Ground meristem: cortex between stele and
epidermis, parechyma cells, stores food,
endodermis single cell layer boundary between
cortex and stele, pericycle inside endodermis
Primary Growth of Stems
• Apical meristem forms primary meristems
(protoderm, ground meristem, and
procambium)
• Procambium forms vascular tissue in
bundles
• Ground meristem forms pith and cortex
• Protoderm forms epidermal tissues
Leaf Growth
• Ground tissues form the mesophyll
• procambium forms the veins
• Protoderm forms the upper and lower
epidermis, guard cells waxy cuticle
Secondary Growth
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Produced by growth in diameter
results from vascular and cork cambium
vascular produces xylem and phloem
cork cambium produces covering of roots
and stems that replace epidermis
• occurs in all gymnosperms and most
angiosperms, rare in monocots
Stages of Differentiation
• Apical meristem
• differentiates into: protoderm, ground meristem,
and procambium
• protoderm differentiations into epidermal
structures
• procambium differentiates into the vascular tissues
• ground meristem produces tissues that fill in
between the epidermis and vascular tissues
Secondary Growth in Stems
• Vascular cambium produces secondary vascular
tissues: xylem--forms wood; phloem--contributes
to the formation of bark and sloughs off
• cork cambium produces the periderm (protective
coat of plant, combination of cork cambium,
layers of cork, and phelloderm,)
• bark-all tissues external to the vascular cambium
Secondary Growth in Roots
• Vascular cambium produces secondary
xylem to the inside and secondary phloem
to the outside
• cortex and epidermis split and are shed as
the stele increases in diameter
• very similar to stems, produces annual rings