Plant Anatomy and Development PDF - University of Saskatchewan

lOMoARcPSD|30352755 Part 1- Plant Anatomy and Development The Living Plant (University of Saskatchewan) Scan to open on Studocu Studocu is not sponsored or endorsed by any college or university Downloaded by Rebeccatheoneandonly ([email protected]) ...

lOMoARcPSD|30352755 Part 1- Plant Anatomy and Development The Living Plant (University of Saskatchewan) Scan to open on Studocu Studocu is not sponsored or endorsed by any college or university Downloaded by Rebeccatheoneandonly ([email protected])  lOMoARcPSD|30352755 Part 1: Plant Anatomy, Growth and Development Lecture 1: The Living Plant  Plants go through life cycles including primary and secondary growth  They have systems similar to humans o Circulatory system (vascular system) o Their pigments absorb light, detect quality, quantity and direction of light o Have stretch receptors o Take in chemical and physical information  Make most of the biomass of the planet  Never run out of food, as long as there is water and sunlight  They are very proliferative, they reproduce rapidly and widely o Seeds and pollen can travel long distances o Have great regenerative capacity. Can regrow branches  Never lonely: most have both male and female organs Growth: can be an increase in size  Adding of new cells, or expanding of cells that already exist  Is not necessarily an increase in physical size, can be dividing of cells but not expansion  There are different dimensions of growth o Meristematic cells are cells which are undifferentiated (think stem cells in humans) Plants have cell walls for structure and protection  Keep the rigid structure of plants, the cells share cell walls  No migration of cells, they do not get cancer Cell Differentiation Development is usually referred to as development of tissues and organs Meristematic cells: are the cells which differentiate into different types of cells Meristem: a region of plant tissue, found chiefly at the growing tips of roots and shoots and in the cambium, consisting of actively dividing cells forming new tissue. Basic Morphology of Vascular Plants Plants have a shoot system and a root system  Are directional classification o Apical and basal, similar to proximal and distal Shoot System  Flower  Terminal Bud (shoot apex): contains the baby cells  Axillary (lateral) bud: leaf axel is the region where the leaf meets the stem Downloaded by Rebeccatheoneandonly ([email protected])  lOMoARcPSD|30352755  Terminal bud (of branch): contains the meristem  Node: where the leaf comes off of the stem  Internode:  Petiole: stalk of the leaf  Stipules: can become thorns or tendrils, are not always present Root System  Taproot: the main root  Lateral roots: branch off of the taproot Lecture 2 Basic Morphology of Vascular Plants (Raven pg. 7-9) The Plant Cell as a Factory Structural components, protection  Cell wall: linked to plasma membrane (included in structure)  Central vacuole: holds water and expands the cell. Helps cell grow o Tonoplast: surrounds central vacuole, deals with pressure “Head Office”  Nucleus: directing the functions within the cell  Nucleolus: makes ribosomes, ribosomal DNA Power Source(s)  Mitochondria: producing ATP with the oxygen that the chloroplasts produce  Chloroplast: needs sunlight as energy, makes sugars for the cell and releases oxygen o Gives green colour (pigment to absorb light) Manufacturing  Making constituents of the cell, cell needs biomolecules i.e. CHO, lipids, protein, DNA  Endoplasmic reticulum o Smooth: no ribosomes, lipid synthesis o Rough: has ribosomes attached, to help with translation of proteins into the ER  Ribosomes: can be free or on the rough ER. Take RNA and translate into protein  Nucleus: makes and stores DNA  Golgi apparatus: protein modification, adding or removing sugars, lipid sidechains, etc. Downloaded by Rebeccatheoneandonly ([email protected])  lOMoARcPSD|30352755 Transit/sorting of biological molecules  Cytoskeleton: cytoplasmic streaming o Microtubules: made of tubulin o Microfilaments: actin o Both move things around the cell like train tracks Storage, is very general  Plastids: many different ones, store biological molecules  Vacuoles can function in storage, smooth ER stores Trade, some molecules are sent to other cells in the plant  Holes in cell walls connect adjacent cells (plasmodesmata movement). Proteins can pass through, lipids, signalling molecules  Some molecules can diffuse through the cell wall Disposal  Lydic vacuole: similar to the lysosome in animal cells o Gets rid of waste products  Secretion outside of the cell  Peroxisomes: break down fatty acids Cell Growth  Cell division  Cell expansion o Elongation  Cell differentiation These three processes occur in an organized spatiotemporal sequence. The zones generally overlap to varying degrees (i.e. they are not discrete regions, with precise borders) Example: stem  Meristem cells are like new floors being built  New cells are added to the top through division  Cells grow bigger as they progress through stages Cell Type Identification Criteria 1. Cell wall: primary or secondary, lignified or non-lignified, uniformity of thickness a. Not all cells have secondary wall, but all have primary b. Lignified: secondary cell walls, most stains are showing lignification (red part usually for lab) Downloaded by Rebeccatheoneandonly ([email protected])  lOMoARcPSD|30352755 c. Some cell walls will be thicker in certain places 2. Cell shape: isodiametric, polyhedral, elongated, branched, etc. a. Isodiametric: same diameter the whole way around b. Polyhedral: many faces, square, etc. 3. Status at maturity: living or dead a. Stains show this 4. Cytoplasmically dense vs. vacuolated a. Dense: involved in metabolism, in meristem or functioning in storage b. Vacuolated: lots of water 5. Distribution throughout the plant a. Some types are only found in one tissue, others are found in many tissues Coleus stem: secondary cell wall is blue, primary cell wall is purple Lecture 3 Plant Cell Basics Cell Walls I. Cellulose microfibril orientation determines cell shape II. Cell shape is created during expansion Inside of a cell, turgor pressure is uniform. Cells deal with uniform pattern by arranging their cellulose microfibrils. Middle Lamella: pectin layer which cements the cell walls of two adjoining plant cells together Downloaded by Rebeccatheoneandonly ([email protected])  lOMoARcPSD|30352755 Primary Cell Wall Structure Cellulose microfibrils made by cellulose synthase enzymes in the plasma membrane  Cellulose synthases: mobile, their trajectories are determined by microtubules  Cell wall formed depending on how microtubules are organized, how the synthases move, then how microfibrils are orientated in the cell wall Cellulose: a CHO Hemicellulose: a shorter, cross-link Pectin: support, mainly in the middle lamella. Takes in water, acts as a buffer Plasmodesmata: allows plants to interact with each other, in the cell walls (holes)  Cells sharing PDs form a “symplasm”  May close off later in differentiation  Can’t be seen with light microscopes, (such as those in labs), need TEM  Desmotubules: strip of the ER that goes through the plasmodesmata Secondary Cell Wall Structure Secondary walls are formed internal to the primary wall, next to the plasma membrane (inside after the primary wall has formed) Alternating cellulose microfibril orientation provides structural fortification because they can resist physical stresses from multiple directions Primary Secondary Deposited as cell is expanding Deposited after the expansion competes (maturation) Thin and more flexible Thick and rigid One layer with middle lamella connecting two Can be multiple layers adjacent walls Don't have lignin (usually) Lignin is always present (large polymers which cross-link  What is being stained in specimens everything, strength) Downloaded by Rebeccatheoneandonly ([email protected])  lOMoARcPSD|30352755 Pits Plasmodesmata clustered into “primary pit fields” become “pits” in the secondary wall  Pit fields are many plasmodesmata clustered together Often can see pits with light microscopes (such as those in lab)  Pit membrane is the remaining area that does not have secondary cell wall; is not a membrane (for water transport) How Prepared Slides are made in lab:  fix specimen  dehydrate it, remove all water (gradual increase in alcohol)  embed specimen in paraffin wax or resin  section with microtone  mount sections on slide  stain (rehydrate a bit)  add coverslip and seal Tissues, Cell Types, Meristems, Secondary Growth Plant Tissue Systems Cells -> tissues -> tissue systems -> organs Downloaded by Rebeccatheoneandonly ([email protected])  lOMoARcPSD|30352755 I. dermal tissue system II. ground tissue system III. vascular tissue system Primary Tissues Secondary Tissues Formed by primary growth Formed by secondary growth (width) Increase in organ length Increase in organ width Herbaceous plant: not woody "Woody" plant, Cells supplied by primary meristems (shoot Cells supplied by secondary meristem apical meristem and root apical meristem) (vascular cambium and cork cambium) All plants have primary growth, not all have secondary growth. Standard Dicot Plants (cross sections), difference in tissue placement and distribution  Stem: distributed vascular tissue  Root: large vascular bundle in centre of the organ  Leaf: large vascular in vein of leaf, netted venation Dermal Tissue System (Chapter 23, p. 553-555) Outermost layer of cells  Controls what goes in and what goes out  Protects from environment  Often covered in a waxy cuticle o Cuticle: up against the cell wall, contains epicuticular wax crystals which help bead water off of leaves  Simple in terms of cell types Dermal tissue cell types in leaves and stems:  Unspecialized “pavement” epidermal cells o Are large cells with odd shapes (puzzle pieces) o General protection and support o Usually no chloroplasts- i.e. no photosynthesis o Intensively studied at molecular level  Guard cells o control gas exchange  water out, CO2 and O2 can enter Downloaded by Rebeccatheoneandonly ([email protected])  lOMoARcPSD|30352755  photosynthesis and respiration o two GCs make a stomatal complex (the hole is the stoma) o can open and close by changes in turgor pressure (positive pressure in cell from vacuoles) o contain chloroplasts, they can photosynthesize o often flanked by subsidiary cells o Usually on lower epidermis: on bottom of leaf there is more air space, where light-independent reactions are occurring o  Trichomes o Gives “fuzzy” leaves and stems their fuzzy features o Protection from insects o Limits water loss from leaf/stem o Protection from high sunlight by reflecting it, which also helps cool the organ o Exclude chemicals for defense or attraction o Glandular (secretory) typically look like stalks o Pluricellular and unicellular (non-secretory) The epidermis is the outermost cell layer of a plant, composed of unspecialized epidermal cells and guard cells. Functions mainly in prevention of water loss (is one cell thick) Root: Epidermis Two epidermal cell types  Hair cells (trichoblasts) o Function: absorb water and nutrients o Increase surface area o Are simpler, unicellular  Non-hair cells (atrichoblasts) o Function: provide support and ensure space between hairs o Space the root hairs out Periderm: the secondary epidermis (of stem)  Derived from secondary meristem called cork cambium  Function is protection and control of water loss  Will discuss later in secondary growth section Ground Tissue System (chapter 23, pg 541-544) Fills space between epidermis and vasculature (in the middle of root)  In stems- cortex and pith o Centre (pith), directly below epidermis (cortex) o Pith: region of primary ground tissue within vascular cylinder Downloaded by Rebeccatheoneandonly ([email protected])  lOMoARcPSD|30352755  In leaves- mesophyll o Middle of leaf (mesophyll)  In roots- cortex (and pith in monocots and gymnosperms) Composed of three tissues  Parenchyma  Collenchyma  Sclerenchyma Parenchyma:  Cells in parenchyma tissue are called parenchyma cells o Chlorenchyma: parenchyma cells which contain chloroplasts for photosynthesis  Living at maturity  Usually only primary walls, but some can be secondary/lignified  Generally simple shapes  May be cytoplasmically dense or vacuolated  Have diverse functions: o Storage of biological material (except DNA)  Starch, protein, water, oil, tannins, crystals o Secretion  Often surrounding a duct within the tissue o Photosynthesis  Leaf mesophyll cells Often found in stem cortex when young (when breaking a twig and it’s green) Cortex: the outermost layer of the stem or root of a plant, bounded on the outside of the epidermis. Usually made of large, thin-walled parenchyma cells of the ground tissue system  These cells can become differentiated, e.g. coleus stem o Redifferentiation of pith parenchyma into xylem Collenchyma:  Cells in collenchyma tissue are called collenchyma cells  Primary walls are non-uniformly thickened  Thickenings mostly cellulose and pectin (a compressible polymer)  Living at maturity  Flexible support in primary/growing tissues (have middle lamella) o Bending a twig, collenchyma supports  Usually found in cortex just underneath epidermis, particularly external to a vascular bundle  Typically elongated Downloaded by Rebeccatheoneandonly ([email protected])  lOMoARcPSD|30352755  Collenchyma location o Usually in the cortex Sclerenchyma:  Cells in sclerenchyma tissue are called sclerenchyma cells  Have secondary walls, often very thick  Dead at maturity  Different shapes  Scler= hard  Types: o Fibers: long and narrow with pointy end walls that overlap  often associated with delicate tissues such as phoelm for protection  rigid support in non-growing tissues, i.e. o Sclereids: lots of shapes  found in groups or alone  provides support and protection  ex: stone cells in a pear fruit, occurring in groups  ex: seed coat: common in hard seed coats of legumes, are columnar shaped  ex: aquatic leaves, provide protection. Dispersed among mesophyll tissue Vascular Tissue I. Xylem a. Transport of water and minerals b. Support c. Food storage II. Phloem a. Transport of sugars and nutrients b. Long-distance signaling (communication) i. Movement of many signaling molecules such as hormones and mRNA Vascular tissue is called a “complex tissue” because Downloaded by Rebeccatheoneandonly ([email protected])  lOMoARcPSD|30352755  In addition to the vascular-specific tissues (xylem and phloem) there are other cell types present, i.e. parenchyma and sclerenchyma  Functions of these cells is same as in ground tissues  Naming is simple o Parenchyma cells in xylem = xylem parenchyma o Parenchyma cells within the phloem = phloem parenchyma Primary vasculature layout:  Often accompanied by bundles of fibers for support/protection Cell types of xylem tissue:  Tracheary elements o Tracheids o Vessel elements  Fibers  Parenchyma Tracheary Elements  Dead at maturity (i.e. cytoplasm and plasma membrane are gone)  Secondary cell walls  Cylindrical with varied diameters  Endwalls typically sloped to varying degrees  Lots of pits of varied patterns and shapes Pits: pit membrane is primary cell wall. Pit membrane is permeable to water, but block air bubbles from moving through from cell to cell. Air bubbles = embolisms (more in physiology section) Downloaded by Rebeccatheoneandonly ([email protected])  lOMoARcPSD|30352755  Vessel element end walls are also known as “perforation plates”. Have a simple perforation plate (a single hole) and compound perforation plate (has several holes)  Allow water and dissolved substances to pass through Tracheary elements: compared to tracheids, vessel elements are  Shorter and wider  Evolutionarily more advanced because they are better conductors due to more diameter  Have perforation plates on end- walls Tracheary element differentiation is programmed cell death Cell Types of Phloem I. Sieve elements Downloaded by Rebeccatheoneandonly ([email protected])  lOMoARcPSD|30352755 a. Sieve tube element and companion cell (angiosperms) i. Supplies information (i.e. DNA) b. Sieve cell and ambulinous cell (gymnosperms) II. Parenchyma III. Sclerenchyma Sieve elements – supply information i.e. DNA  Living at maturity, but organelles are mostly degenerated  Filled with “phloem sap”  Primary cell walls only  Cell shape: cylindrical and elongated  Have a sieve plate (instead of perforation plate) o Allows passage of water and dissolved substances Sieve tube element/companion cell morphologies:  End-walls sloped to varying degrees  Simple or compound end plates  Variation in pattern of lateral sieve areas  companion cells can be one or more per element  no sieve plates in gymnosperms (overlapping lateral sieve areas)  sieve pores: larger on sieve plate than lateral sieve area I. simple = entire plate is a single sieve area II. Compound = plate has multiple sieve areas Function of the P-Protein:  During injury, forms a slime plug to seal off the cell (similar to blood clot)  May regulate conductivity of sieve element Downloaded by Rebeccatheoneandonly ([email protected])  lOMoARcPSD|30352755 Phloem development:  Transition from plasmodesmata to sieve pore  Movement and repurposing of the P-protein  Callose helps pore develop (is temporary)  Nucleus degenerates Monocots vs Eudicots (Dicots) Key differences: vasculature  Patterns of vasculature is different  Stem: Downloaded by Rebeccatheoneandonly ([email protected])  lOMoARcPSD|30352755 o Monocot: vascular bundles scattered throughout o Dicot: vascular bundles around the perimeter  Roots: o Monocot: has pith in middle o Dicots: no pith, central vascular cylinder  Leaves: o Monocot: leaves are parallel to one another o Dicot: long vascular tissue in leaves Meristems, Secondary Growth (chapter 25, pg. 580-602) Apical (primary) meristems  Cell division centers  Small, cytoplasmically dense, undifferentiated cells (similar to stem cells)  Needs to maintain cells within the meristem (balance of cells for self and for distribution)  Initials give rise to derivatives (divide their whole life) Initials and derivatives  initial will divide  derivative will differentiate and grow, lengthen o can divide, themselves SAM and RAM  Shoot Apical Meristem (SAM), part of plant that we see  Root Apical Meristem (RAM) o Lateral roots do not come from meristem Downloaded by Rebeccatheoneandonly ([email protected])  lOMoARcPSD|30352755 The Primary Plant Body Apical meristem will branch into three areas, primary meristems will make primary tissues Downloaded by Rebeccatheoneandonly ([email protected])  lOMoARcPSD|30352755 Root: meristems and Tissues  Derivative sits at the meristem Downloaded by Rebeccatheoneandonly ([email protected])  lOMoARcPSD|30352755 Rootcap: protection as the root pushes through the soil Procambium: beginning to differentiate, no xylem or phloem (are precursor cells) Three primary (apical) meristems:  Protoderm Downloaded by Rebeccatheoneandonly ([email protected])  lOMoARcPSD|30352755  Ground mesoderm  Procambium: cells are still meristematic, usually go dormant (unless secondary growth) *note: residual procambium is also called a fascicular cambium Tissues Are Established during embryogenesis Downloaded by Rebeccatheoneandonly ([email protected])  lOMoARcPSD|30352755 Axis of plant established in the seed, root and leaves Primary meristems give rise to primary tissues Tunica-corpus:  SAMs can also be described as having a “tunica-corpus” organization o A cover (tunica) body (corpus) o A sheet over a body  Tunica-corpus essentially means there are zones of cell division o Central zone: cells divide sideways to make room for new cells o Peripheral zone: divide downwards along the sides o Pith meristem  Two tunica layers: cell division orientations Downloaded by Rebeccatheoneandonly ([email protected])  lOMoARcPSD|30352755  Two division plane orientations (also used to refer to the cell wall divisions) o Anitclinal: cell wall is perpendicular to the surface  Occurring in tunica layers, increase area of the sheet o Periclinal: cell wall is parallel to the surface  Looking at periclinal walls when you look at a plant Primary Tissue Differentiation in Stem Primary xylem development  Protoxylem: cease differentiation before stem has stopped elongating o First to form o Differentiation has completed before elongation of the organ has completed  Metaxylem: o Begins formation later than protoxylem o Differentiation completes after elongation of the organ has completed Protoxylem Metaxylem Primary Phloem  Protophloem: formed first,  Metaphloem: formed later, transports molecules Remember: phloem does not have a secondary cell wall Open vs. Closed Vascular Bundles  Bundle sheath: protects the vascular bundles Monocot (Zea mays) vascular bundle differentiation Downloaded by Rebeccatheoneandonly ([email protected])  lOMoARcPSD|30352755 Secondary Meristems I. Vascular cambium a. Makes secondary xylem b. Makes secondary phloem II. Cork cambium (phellogen) a. Makes periderm (surrounding skin) Formation of Secondary tissues:  Secondary growth (from secondary meristem) increases the thickness of the plants  Herbaceous plants do not have secondary growth  First step: formation of interfascicular cambium from fascicular cambium  Makes cells in two directions o New xylem on inside (red) o New phloem on inside (blue) (periclinal divisions inside of the fascicular cambium). There is much more secondary xylem produced than secondary phloem Formation of Periderm  No cambium activity yet  Cork cambium formed and one division each side o Cork cells mostly formed towards the outside o Most of the periderm come from cork cambium  Now it has made three cork layers, and still one phelloderm Downloaded by Rebeccatheoneandonly ([email protected])  lOMoARcPSD|30352755 o Phelloderm: to the inside of the cork cambium  Selective growth by the cortex layers breaks the epidermis o Done to have better access to oxygen Periderm vs Bark  Bark is all tissues outside of the vascular cambium  Two parts of bark: o Outer bark = dead  Phellum (cork) and epidermis o The inner bark = living Downloaded by Rebeccatheoneandonly ([email protected])  lOMoARcPSD|30352755 Wood Anatomy Bark: periderm, secondary phloem, and vascular cambium Heartwood: middle, almost all dead.  No living parenchyma.  Nonconductive, contains resins and tannins to provide strength Sapwood: active wood, is conductive (xylem sap) Growth Rings:  Form as a result of seasonal slowing/ cessation of vascular cambium o Early and late growth vessels Downloaded by Rebeccatheoneandonly ([email protected])  lOMoARcPSD|30352755  Early wood (lighter, less dark) – in spring o A lot of expansion  Late wood (darker/denser)  Variable based on the environment We can see that this tree was cut in the winter because there are no earlywood vessels, which would grow during the spring months Downloaded by Rebeccatheoneandonly ([email protected])  lOMoARcPSD|30352755 Xylem Ray Radial Rays (a secondary tissue):  Transport in/out  Use of parenchyma cells connecting outermost part of phloem to inner most part of xylem  Phloem rays and xylem rays depending on location in stem Angiosperm woods (i.e. secondary xylem): mainly tracheids  Two types of parenchyma cells o Ray parenchyma (radial transport and storage) o Axial parenchyma. Part of a column around the vessel elements (oriented axially) Angiosperm cross sections: (lecture 8)  Transverse face:  Radial face: through the centre o Can see rays (appear in groups or lines) o Can see vessels and perforation plates  Tangential face: o See rays (different than radial), they look like fish Gymnosperm cross sections: no vessels  Transverse:  Radial: Downloaded by Rebeccatheoneandonly ([email protected])  lOMoARcPSD|30352755  Tangential: can see pits (?) Downloaded by Rebeccatheoneandonly ([email protected])  lOMoARcPSD|30352755 Vascular Cambium Structure and Divisions Initials and derivatives Two types of initials in the vascular cambium:  Fusiform initials o Generate treacheary elements (towards inside) o Generate sieve elements (towards the outside)  Ray initials (dark green in diagram) o Generate ray cells **** Lengths of initials match length of derivatives: both do primarily periclinal division Remember vascular cambium can be multiple cell layers thick Downloaded by Rebeccatheoneandonly ([email protected])  lOMoARcPSD|30352755 Embryos and Embryogenesis Note: many terms at the end of lab 3 in lab manual Seedling basic body plan: Eudicot (Dicot) I. Two patterns established during embryogenesis a. Apical-basal b. Radial Endosperm:  Provides nutrients to developing embryo  Depending on the species: o Endosperm remains during embryogenesis to nurture the embryo o Endosperm gets sucked into the cotyledons, which then nourish the embryo When endosperm remains: When endosperm goes into cotyledons: Radicle: embryonic root In monocots, the cotyledon is called a scutellum Downloaded by Rebeccatheoneandonly ([email protected])  lOMoARcPSD|30352755 Monocot Seed Structure: Maize Monocot specifics: Coleoptile and the coleorhiza ->  Coleorhiza: protects the radicle  Adventitious root: derives from stem tissue, is not a meristem  Note: good diagram in lecture 9 Downloaded by Rebeccatheoneandonly ([email protected])  lOMoARcPSD|30352755 Germination The moment when the radicle first breaks through the seed coat Seedling germination: two types I. Epigeous a. Cotyledons come out of the ground with the leaves II. Hypogeous a. Cotyledons stay underground Dicot epigeous germination Dicot hypogeous germination Downloaded by Rebeccatheoneandonly ([email protected])  lOMoARcPSD|30352755 Monocot epigeous germination Monocot hypogeous germination Downloaded by Rebeccatheoneandonly ([email protected])