[bio] 04 - Plant Tissues (calsado)

Plant tissues

PLANTS Photosynthetic autotrophs Obtain inorganic materials from the external

environment and process them into the organic compounds needed for life Cells secrete a cell wall exterior to the plasma membrane

Plant Propagation Asexual/vegetative reproduction Clone Meristems Special types found at the growing tips, other

parts Similar to proembryo, all cells can differentiate

Adventitious Plant parts produced by dedifferentiation

Complexity Dispersal means Most primitive: spores More complex: seed Conducting/vascular tissue Simpler plants: no conducting tissues  Complex plants: with vascular tissues

Plant Organization Root system- growth toward gravity; generally

below ground; consists of roots

Root – epidermis; cortex; stele (vascular tissue);

pith

Shoot system Growth away from gravity along the axis Generally above the ground Consists of the stem and the leaves Flowers are modified shoot system

Plant Tissues Meristems Surface or dermal tissues Vascular tissues Ground or fundamental tissues

Meristems Responsible for increase in number of cells Meristems do not specialize Plant tissues are derived from the meristems Three types: Apical Lateral Intercalary

Meristems Intercalary Meristem- plants without vascular

cambium (grasses) Growth regions that occur at the base of nodes

Growth Primary growth Inc in length of plants (apical meristem) Secondary growth Inc in plant girth (lateral meristem) Select plants only (woody plants such as dicot

and gymnosperms) Product: wood and cork

Plant growth patterns and regions Primary growth- growth in length; primary

meristems Secondary growth- growth which increases the girth or circumference of the plant Vascular cambium- bet wood and bark Cork cambium-found in the outer bark

Primary meristems At tips Shoot tip meristems (shoot system) Stem meristem; leaf primordia; bud primordia Root tip meristems Primary meristems are permanent and self

perpetuating

Derivative meristems Produced when meristem cells divide; forms

the tissue systems of the plant Protoderm- develops into surface or dermal tissues  Procambium- develops into vascular tissue  Ground meristem- fundamental /ground tissues  Secondary meristems  Vascular cambium- produces wood (strength); produces part of bark (protection)  Cork cambium- produces protective layer of bark called cork 

Plant Growth Primary Growth

(roots and shoots)

Secondary

Growth (roots and shoots)

Meristems from Cell Dedifferentiation Dedifferentiate-any plant cell has the ability

to dedifferentiate Lateral root formation  Adventitious growth  Wound healing  Secondary cork cambium 

Primary Growth of Roots Root cap protects the delicate meristems as the root elongates through the abrasive soil  secretes mucous that lubricates the soil 

3 Zones of cells at successive station Zone of cell division  Zone of cell elongation  Zone of cell differentiation 

Simple Tissues

Ground or fundamental tissues Fibers- for support Photosynthetic cells Storage cells Fill in the spaces cells

Ground or Fundamental Tissues Parenchyma basic tissue type

Collenchyma supports young plants

Sclerenchyma supports for mature plants

Parenchyma Definition: a simple tissue composed of spherical-

shaped cells; most common type of tissue Have thin primary walls Living, metabolizing tissue E.g. Chlorenchyma, Aerenchyma Functions:  Photosynthesis & Respiration  Storage (starch, oil droplets, air, water, and salts)  Wound healing & regeneration

Collenchyma Definition: a simple tissue found beneath

the epidermis in young stems and in large veins of leaves (“strings” in celery). Provides a flexible support system (like our skeletal system). Found uniformly throughout the plant. Elongated cells that have unevenly thickened cell walls (especially in the corners) Alive at maturity

Sclerenchyma Definition: a simple tissue

specialized for structural support; occurs in many areas Two types: Fibers Sclereids

Have both primary and

secondary cell walls. At functional maturity cells are often dead

Fibers Long, tapered cells that often occur in groups or clumps (abundant in the wood and bark of flowering plants) Found in leaves & stems. Primary function is support

Sclereids Short, cuboidal cells common in shells of nuts and pits of fruits (peaches, cherries) Found in all plant parts, usually clustered. Primary function is for protection

Complex tissues Vascular Tissue System

Vascular tissues Functions: conduct water and solutes

support and strength of the plant Types of vascular tissues Xylem- conducts water and minerals Phloem- conducts solutes/food Continues throughout the plant

Xylem Conduction of H2O from roots to leaves Made up the wood Composed of: Vessel Elements- elongated cells with secondary walls  Dead at functional maturity; perforated  Large diameter  Tracheids – elongated, narrow cells with secondary walls; dead at functional maturity; pitted  Xylem fibers  Xylem parenchyma  Xylem rays  Parenchyma cells and Fibers 

Tracheids Tracheids are typically found in

gymnosperms and seedless vascular plants and aid in transporting water.

Vessel Elements Vessel elements

are typically found in angiosperms and aid in transporting water.

Phloem Moves solutes (especially carbs) Composed of: Sieve tube cells  Elongated

cells forming tubes  End walls have pores forming sieve plates  Alive at functional maturity  Carry food

Companion cells  Parenchyma cells adjoining the sieve tube cells  Phloem fibers  Phloem parenchyma (Sclerenchyma fibers and parenchyma cells)

Sieve tube members Sieve tube members

can secrete a protein called callose to plug sieve plates to stop the flow of food if the phloem is damaged

Complex tissues Dermal Tissues

Surface or dermal tissues Protection

Prevents dessication

Dermal (surface) tissue Epidermis (herbaceous plants) 

Cuticle (protective waxy layer)- prevents dessication (cuticle) and invasion of pathogens , absorption of water, control of gas exchange

Periderm or cork layer (woody plants) Produced from cork cambium  Secondary epidermis or periderm of woody plants 

Dermis Epidermis: Two types Parenchyma cells Guard cells NO Chloroplasts

Cuticle A waxy layer

secreted by epidermal cells of stems and leaves Prevents water loss and diffusion of gases Cuticle

Parenchyma cells

Guard cells Guard cells form the tiny opening called the

stomata

Peridermis Woody plants initially produce an epidermis that

splits as the plant grows. These plants also have periderm, which is several cells thick and forms under the epidermis. Periderm composes the outer bark Composed of two types of cells  Cork

cells- secrete suberin  Cork parenchyma

Dermal (surface) tissue Epidermal modifications Hairs of trichomes Root hairs: absorption of water  Guard cells: form stomata for gas exchange  Glands: modified cells containing oils or other substances for secretion 

Transport in Plants Cellular level transport Lateral transport Long-distance transport

Plant Nutrition Chemical composition of plants 80%-85% of herbaceous plants is H2O Plants grow mainly by accumulating water in

the central vacuoles of their cells Carbon, hydrogen, oxygen are the most abundant elements in the dry weight of a plant

Essential Nutrients Hydroponic structure- used to determine

which of the mineral elements are actually essential nutrients Macronutrients- elements required by plants in relatively large amounts Micronutrients- elements needed by plants in small amounts