Introduction to Botany. Lecture 18 - Materials of Alexey Shipunov

Outline1 Questions and answers2 TissuesOrigin of tissuesStep four: pipes. Vascular tissuesXylemPhloemShipunov (MSU) Introduction to Botany. Lecture 18 October 17, 2014 2 / 26

Outline1 Questions and answers2 TissuesOrigin of tissuesStep four: pipes. Vascular tissuesXylemPhloemShipunov (MSU) Introduction to Botany. Lecture 18 October 17, 2014 2 / 26

Questions and answersPrevious final question: the answerWhat is the difference between collenchyma and sclerenchyma?Shipunov (MSU) Introduction to Botany. Lecture 18 October 17, 2014 3 / 26

Questions and answersPrevious final question: the answerWhat is the difference between collenchyma and sclerenchyma?Alive vs. deadPrimary vs. secondary cell wallsShipunov (MSU) Introduction to Botany. Lecture 18 October 17, 2014 3 / 26

TissuesOrigin of tissuesOrigin of tissues and organs of plants: first stepsPlants were pushed on land for many reasons, includingcompetitionFirst challenge: drying. Response: epidermis and parenchyma.Second challenge: new level of competition. Response: growingup!Problem: big weight. Response: collenchyma.Competition grows, plants growing even higher. Weight grows.They also need to get rid of turgor dependency. Response: uselignin not only for epidermis surface (cuticle) but also forsecondary cell walls—sclerenchyma.Competition grows again, plants need to grow faster. Solution:meristems.Size of plant is too big for plasmodesmata transportations.Solution: vascular tissues, xylem and phloem.Shipunov (MSU) Introduction to Botany. Lecture 18 October 17, 2014 5 / 26

LigninTissuesOrigin of tissuesPhenolic compounds (e.g., lignin) were initially developed for sporedistribution with a wind, then used in cuticle, then in the secondary cell walls.Shipunov (MSU) Introduction to Botany. Lecture 18 October 17, 2014 6 / 26

TissuesStep four: pipes. Vascular tissuesTissuesStep four: pipes. Vascular tissuesShipunov (MSU) Introduction to Botany. Lecture 18 October 17, 2014 7 / 26

Vascular tissues: XylemTissuesStep four: pipes. Vascular tissuesOccurs in vascular bundles or vascular cylinderTypes of cells: tracheary elements (tracheids and vessel members),fibers, and parenchymaTracheids have pits; vessel members have perforations; all of them aredead cellsGymnosperms have only tracheids; flowering plants have tracheids +vessel elements togetherIn flowering plants, primary xylem has mostly tracheids and vessels withscalariform perforations; secondary xylem has mostly vessels with openperforationsXylem elements (except parenchyma) are rich of lignin and are maincomponents of woodMain functions: water transport and mechanical supportShipunov (MSU) Introduction to Botany. Lecture 18 October 17, 2014 8 / 26

TissuesVessel members vs. TracheidsStep four: pipes. Vascular tissuesShipunov (MSU) Introduction to Botany. Lecture 18 October 17, 2014 9 / 26

TissuesVessel members vs. TracheidsStep four: pipes. Vascular tissuesShipunov (MSU) Introduction to Botany. Lecture 18 October 17, 2014 10 / 26

TracheidsTissuesStep four: pipes. Vascular tissuesPine (Pinus sp.) tracheids with pitsShipunov (MSU) Introduction to Botany. Lecture 18 October 17, 2014 11 / 26

TissuesPit is NOT a direct connectionStep four: pipes. Vascular tissuesShipunov (MSU) Introduction to Botany. Lecture 18 October 17, 2014 12 / 26

VesselsTissuesStep four: pipes. Vascular tissuesAsh (Fraxinus americana) secondary xylemwith vessels (LM ×26)Shipunov (MSU) Introduction to Botany. Lecture 18 October 17, 2014 13 / 26

PerforationsTissuesStep four: pipes. Vascular tissuesShipunov (MSU) Introduction to Botany. Lecture 18 October 17, 2014 14 / 26

TissuesStep four: pipes. Vascular tissuesScalariform perforations: direct connectionsShipunov (MSU) Introduction to Botany. Lecture 18 October 17, 2014 15 / 26

PhloemTissuesStep four: pipes. Vascular tissuesUsually occurs adjacent to a xylemTypes of cells: sieve tube cells, companion cells, fibers andparenchymaSieve tube cells have plastids and perforation (sieve) platesbetween cells but no nuclei, companion cells have nucleiHowever, in gymnosperms there are no companion cells and sievetube cells have nucleiSecondary phloem usually has more fibers than primary phloemMain functions: sugar transport and mechanical supportShipunov (MSU) Introduction to Botany. Lecture 18 October 17, 2014 16 / 26

Phloem cell typesTissuesStep four: pipes. Vascular tissuesShipunov (MSU) Introduction to Botany. Lecture 18 October 17, 2014 17 / 26

TissuesStep four: pipes. Vascular tissuesSieve tubes and phloem parenchymaShipunov (MSU) Introduction to Botany. Lecture 18 October 17, 2014 18 / 26

Perforation (sieve) plateTissuesStep four: pipes. Vascular tissuesCross-section (TEM)Shipunov (MSU) Introduction to Botany. Lecture 18 October 17, 2014 19 / 26

Plates: frontal viewTissuesStep four: pipes. Vascular tissuesFrontal view (LM)Shipunov (MSU) Introduction to Botany. Lecture 18 October 17, 2014 20 / 26

Plates: poresTissuesStep four: pipes. Vascular tissuesSieve plate, a pore in the end wall of a sieve-tube member, throughwhich phloem sap flows (SEM ×4800)Shipunov (MSU) Introduction to Botany. Lecture 18 October 17, 2014 21 / 26

TissuesPrimary vascular tissuesStep four: pipes. Vascular tissuesShipunov (MSU) Introduction to Botany. Lecture 18 October 17, 2014 22 / 26

TissuesSecondary vascular tissuesStep four: pipes. Vascular tissuesShipunov (MSU) Introduction to Botany. Lecture 18 October 17, 2014 23 / 26

TissuesFinal question (2 points)Step four: pipes. Vascular tissuesShipunov (MSU) Introduction to Botany. Lecture 18 October 17, 2014 24 / 26

TissuesFinal question (2 points)Step four: pipes. Vascular tissuesWhat are more primitive states for xylem and phloem, respectively?Shipunov (MSU) Introduction to Botany. Lecture 18 October 17, 2014 24 / 26

SummaryTissuesStep four: pipes. Vascular tissuesXylem vs. phloem:State: dead vs. living cellsTransport: water vs. sugarDirection: up vs. downBiomass: big vs. smallShipunov (MSU) Introduction to Botany. Lecture 18 October 17, 2014 25 / 26

For Further ReadingTissuesStep four: pipes. Vascular tissuesA. Shipunov.Introduction to Botany [Electronic resource].2010—onwards.Mode of access:http://ashipunov.info/shipunov/school/biol_154Th. L. Rost, M. G. Barbour, C. R. Stocking, T. M. Murphy.Plant Biology. 2nd edition.Thomson Brooks/Cole, 2006.Chapter 4.Shipunov (MSU) Introduction to Botany. Lecture 18 October 17, 2014 26 / 26