Plant Structure and Function Ch 29

Plant Structure and Function Ch 29 • Check Ch 28 GRQ’s – Any Q’s • Intro to Ch 29 Plant Structure/Transport/Function.

Chapter 29: Plant Structure and Growth • Plants are: • Multicellular, • autotrophic • eukaryotes • Cell walls of cellulose • Alternation of generations

Plants are composed of: • Cells (3 major types) • Tissues (also 3 types) • Organs ( roots/stems/leaves) • Organ systems (roots/stems)

Three Plant CellTypes • Parenchyma • Thin walls/flexible cells • Carry out many basic fxns such as photosynthesis • Collenchyma • Thicker cell walls/ grouped in strands/ for support • Think Celery stalks • Sclerenchyma • Thick cell walls for support, cells are often dead. • Shells around nuts have many

Three Plant Tissue Systems • Dermal Tissue (the skin) • Epidermis (nonwoody) • Single layer • Periderm (woody) • Vascular Tissue (the circulatory system) • Xylem (vessel element) • Phloem (sieve tube/companion) • Ground Tissue • Photosynthesis & storage (ex water storage in Cacti)

Organ Systems • Root system • Shoot system • Stems • Leaves

Root Structure • Root structure is organized for growth and absorption of nutrients. • Root Function..?

Roots • Function: • anchor or support • water and mineral absorption • Storage • Tiny roots hairs increase surface Area for absorbing water • symbiotic associations • bacteria • fungi

Shoots: (stems & leaves) • Stems • Alternating nodes and internodes • At nodes: • Leaves, buds, branches • Buds: • terminal buds • growth at tip • axillary buds • growth of branches(Lateral) • Functions

Growth • Animal growth is determinant (stops @ some point) • Also plant leaves and flowers • Plant growth is indeterminant (continues throughout life) • Meristems

Plant Growth • Meristems contain embryonic tissue • Apical meristems provide growth in length • in tips of shoots (buds) and roots • primary growth • Lateral meristems provide growth in width • only in woody plants • secondary growth

Primary Growth: Roots • Apical meristem - • zone of cell division • gives rise to the three primary tissue types • zone of elongation • zone of maturation

Primary Growth: Shoots • Apical meristems are in buds • give rise to new stems, leaves, and axillary buds

Secondary Growth • Lateral meristems  growth in width • secondary growth • only in woody plants • There are two lateral meristems • vascular cambium • produces 2o xylem & phloem • cork cambium • produces cork

Secondary Growth: Vascular Cambium • located between xylem and phloem • produces 2o xylem to inside, 2o phloem to outside • 2o xylem is called “wood” x p

Secondary Growth: Vascular Cambium • each year’s growth of xylem becomes a ring • most recent 2o growth is nearest cambium • 2o phloem lies in bark

Secondary Growth: Cork Cambium • Cork cells develop waxy coat • Periderm is cork & cork cambium • “Bark” is cork & cambium & 2o phloem • Girdling a tree kills it by removing the phloem cc cork

Overall structure: Leaves • Leaves • adapted for photosynthesis and gas exchange

Transport in Plants • How do they do that? • Transport occurs at three levels: • cellular • cell-to-cell • plasmodesmata • long-distance bulk flow • Passive & active transport involved

Plant Cell Types • Xylem (vessel elements) • Water- and mineral- conducting • dead at maturity / 2o cell wall • pores provide continuity • Phloem (sieve tube and companion cell) • live at maturity • Sugar-conducting • end-to-end tubes have pores

Roots: water & mineral absorption • Apoplastic (within walls) and symplasticroutes (through cells)

Root hairs 37.12 and mycorrhizae

Roots: water & mineral absorption • Endodermis is a selective barrier • Determines what enters stele • Apoplast ends at endodermis • Casparian strip

Water movement: roots to leaves • Is water pushed or pulled up xylem? • It’s pushed for short distances – root pressure • But mainly…

…Xylem sucks • Transpiration pull in leaves

Water movement: roots to leaves • Transpiration-cohesion-tension-mechanism

Stomata control transpiration • Transpiration-photosynthesis compromise • open during day - closed at night Two Guard cells

Stomata control transpiration • Opened by: • photosynthesis • low CO2 in leaf • circadian rhythm • K+ regulates stomata opening • When K+ is pumped in • Water follows  turgid • Stoma opens • When K+ is pumped out • Water follows  flaccid • Stoma closes

Bulk flow/Pressure flow/TranslocationAKA - Phloem movement • Sap flows from sugar source to sugar sink

Phloem movement • Source: • sugar loaded into phloem via active transport (cotransport) • this initially reduces the ys(i.e., below zero) • water flows in, raising yp(hydraulic pressure)

Phloem movement • Sink: • sugar unloaded from phloem via active transport (cotransport) • this initially raises the ys (i.e., toward zero) • water flows out, lowering yp (hydraulic pressure) • Note: xylem-phloem link

HW for Thursday 4/17 • Plant BIG GRQ’s

Plant Structure and Function Ch 29