Botany Secondary Growth PDF

BOT2010 GENERAL BOTANY SLIDE SET 14: Secondary Growth 01 Table of Contents 31 Wood Cuts: Radial – 3 02 Secondary Growth 32 Wood Cuts: Tangential – 1 03 Origin of Secondary Tissues 33 Wood Cuts: Tangential – 2 04 Vascular C...

BOT2010 GENERAL BOTANY SLIDE SET 14: Secondary Growth 01 Table of Contents 31 Wood Cuts: Radial – 3 02 Secondary Growth 32 Wood Cuts: Tangential – 1 03 Origin of Secondary Tissues 33 Wood Cuts: Tangential – 2 04 Vascular Cambium 34 Wood Cuts: Tangential – 3 05 Vascular Cambium Development 35 Wood Cuts: Douglas Fir 06 Cork Cambium 36 Wood Cuts: Eastern White Pine 07 Cork Cambium Development 37 Wood Cuts: Northern Red Oak 08 Three-Year Woody Dicot Stem 38 Wood Cuts: Basswood 09 Cork 10 Cork Cambium 11 Phelloderm 12 Parenchyma 13 Primary Phloem 14 Secondary Phloem 15 Vascular Cambium 16 Secondary Xylem 17 Primary Xylem 18 Ray Parenchyma 19 Pith Parenchyma 20 Heart Wood v Sap Wood 21 Spring Wood v Summer Wood 22 Wood v Bark: Wood 23 Wood v Bark: Bark 24 Lenticels 25 Wood Cuts 26 Wood Cuts: Transverse – 1 27 Wood Cuts: Transverse – 2 28 Wood Cuts: Transverse – 3 29 Wood Cuts: Radial – 1 30 Wood Cuts: Radial – 2 SECONDARY GROWTH Increases girth of woody dicot plants Secondary meristems  Vascular cambium  Fasicular cambium  Interfasicular cambium  Cork cambium OLDER SHOOT Produce secondary tissues  Secondary xylem  Secondary phloem  Cork  Phelloderm Occurs in both stems & roots OLDER ROOT  ORIGIN OF SECONDARY TISSUES ORIGIN SECONDARY MERISTEM SECONDARY TISSUE Fasicular cambium (procambium) Secondary xylem Vascular cambium Interfasicular cambium Secondary phloem (ray parenchyma) Cork Cortex parenchyma Cork cambium Phelloderm VASCULAR CAMBIUM SECONDARY MERISTEM Continuous ring of cells formed from fasicular & interfasicular cambium Major plane of cell division rotated 90° from perpendicular to parallel to stem longitudinal axis Produces secondary xylem to inside & secondary phloem to outside of vascular cambium Secondary xylem persists for life of tree VASCULAR CAMBIUM DEVELOPMENT SECONDARY MERISTEM Vascular cambium  Fasicular cambium  Interfasicular cambium Development of fasicular cambium  Fasicular cambium = procambium Development of interfasicular cambium  Parenchyma cells in ray region dedifferentiate  Become meristematic cells  Form continuous ring with fasicular cambium CORK CAMBIUM SECONDRY MERISTEM Produces cork to the outside of cork cambium Produces phelloderm to the inside of cork cambium CORK CAMBIUM DEVELOPMENT SECONDARY MERISTEM Formed each year Parenchyma cells in cortex dedifferentiate  Forms secondary meristem Produces secondary tissues  Cork  Phelloderm THREE-YEAR OLD WOODY DICOT STEM PRIMARY & SECONDARY TISSUES Primary & secondary tissues (ordered from outside to inside)  Cork  Cork cambium  Phelloderm  Parenchyma  Primary phloem (only 1st year)  Secondary phloem  Vascular cambium (2° meristem)  Secondary xylem  Primary xylem  Ray parenchyma  Pith parenchyma CORK SECONDARY TISSUE Characteristics Function Formed by  Outermost layer  Protection second & all  Cell walls contain suberin (wax)  Water-proofing subsequent  Dead when functional  Insulation divisions of cork cambium CORK CAMBIUM SECONDARY MERISTEM Characteristics  Located beneath cork  Replaced every year CORK Function CORK CAMBIUM  Produces cork cells to outside  Produces phelloderm cells to inside PHELLODERM SECONDARY TISSUE Characteristics  Formed by cork cambium  Layer 1 cell thick CORK Formed by first division of CORK CAMBIUM cork cambium PHELLODERM Function  Unknown PARENCHYMA PRIMARY TISSUE Characteristics  Cortex region  Crushed as time passes CORK Function CORK CAMBIUM  Dedifferentiates to form PHELLODERM cork cambium CORTEX PARENCHYMA PRIMARY PHLOEM PRIMARY TISSUE Characteristics  Formed by procambium during first few months of growth  As tree trunk ages, becomes crushed & sloughed with bark Function  Translocates food when first formed SECONDARY PHLOEM SECONDARY TISSUE Characteristics  Formed by vascular cambium  No growth rings visible  As tree trunk ages, becomes crushed & sloughed with bark Function  Transports food when first formed VASCULAR CAMBIUM SECONDARY MERISTEM Characteristics  Formed from procambium & parenchyma ray cells  Eternally juvenile tissue that continuously divides Function  Produces phloem cells to outside  Produces xylem cells to inside SECONDARY XYLEM SECONDARY TISSUE Characteristics  Formed by vascular cambium  Growth rings present  Layers of cells within each year’s growth (ring)  Large cells = spring wood (early wood)  Small cells = summer wood (late wood)  Growth rings retained for life of tree Function  Conduct water & minerals (Limited to most recent growth, 1–3 years) PRIMARY XYLEM PRIMARY TISSUE Characteristics  Formed by vascular cambium during first 3 months of growth  Innermost layer of xylem Function  Conducts water & minerals when first formed RAY PARENCHYMA PRIMARY TISSUE Characteristics  Extend laterally across stem from pith region to outer edge of phloem  Arranged like spokes on wheel Function  Lateral transport PITH PARENCHYMA PRIMARY TISSUE Characteristics  Primary tissue located at center of tree trunk  After 5–10 years, crushed due to lateral expansion of trunk & no longer recognizable as parenchyma  As tree ages, resins collect & contribute to formation of heart wood HEART WOOD v SAP WOOD Heart wood  Located at center of tree trunk  Reddish brown color  Resins accumulate  Extra hard  Natural insecticide  Preferred for construction Sap wood  Yellowish color  No or very little resins  Cells filled with water, but only youngest layers conduct water  Softer wood  Young trees have mostly sap wood SPRING WOOD v SUMMER WOOD Spring wood  Typically formed in spring  Water readily available  Form large vessel elements Summer wood  Typically formed in summer  Water less readily available  Form smaller vessel elements Progression from large to small vessel elements during growing season forms growth rings WOOD v BARK: WOOD Consists of all layers of the xylem  Includes all parts of trunk inside vascular cambium Characteristics  Has growth rings  Retained for life of tree  Harvested for lumber  Youngest wood layers conduct water & minerals WOOD v BARK: BARK Includes all parts of stem outside vascular cambium  Secondary phloem  Primary phloem (if present)  Cortex parenchyma  Phelloderm  Cork cambium  Cork Characteristics  Repeatedly crushed as sloughed off as tree ages  No growth rings  Functions to protect tree trunk  Phloem translocates food LENTICELS Eruptions in bark  At cellular level, look like volcano  Layers of cork raised exposing cortex parenchyma to external atmosphere Functions in gas exchange  Some water vapor lost  Non-photosynthetic cells require O2 for aerobic respiration which produces CO2 WOOD CUTS Planes of sectioning  Transverse  Radial  Tangential WOOD CUTS: TRANSVERSE – 1 TRANSVERSE CUT Transverse cut  Cross section or cut parallel to earth’s surface TRANSVERSE CUT  Rays appear as spokes on wheel  Growth rings form concentric circles  Cut used to fell trees WOOD CUTS: TRANSVERSE – 2 GROSS ANATOMICAL LEVEL DOUGLAS FIR EASTERN WHITE PINE NORTHERN RED OAK BASSWOOD WOOD CUTS: TRANSVERSE – 3 MICROSCOPIC LEVEL Transverse section  Cross section (XS)  Vessel elements & tracheids appear as circles; length of these cells not visible  Rays appear as spokes on wheel  Spring & summer wood of growth ring clearly visible  WOOD CUTS: RADIAL – 1 RADIAL CUT Radial cut  Longitudinal section or cut perpendicular to earth’s surface  Cut passes through center of trunk or trunk radius  Rays appear as horizontal streaks  Growth rings appear as longintudinal lines  More expensive cut of lumber RADIAL CUT WOOD CUTS: RADIAL – 2 GROSS ANATOMICAL LEVEL DOUGLAS FIR EASTERN WHITE PINE NORTHERN RED OAK BASSWOOD WOOD CUTS: RADIAL – 3 MICROSCOPIC LEVEL Radial cut  Longitudinal section (LS) through center of stem  Longitudinal axis of vessel elements & tracheids visible; appear as long cells  Rays appear as low, brick walls  Growth rings difficult to discern but alternating layers of large & small cells visible WOOD CUTS: TANGENTIAL – 1 Tangential cut  Longitudinal section or cut perpendicular to earth’s surface  Any longitudinal cut not TANGENTIAL CUT through center of tree trunk  Rays appear as short, perpendicular flecks or streaks  Growth rings form ellipses or pattern of “normal curve”  Less expensive cut of lumber TANGENTIAL CUT WOOD CUTS: TANGENTIAL – 2 GROSS ANATOMICAL LEVEL DOUGLAS FIR EASTERN WHITE PINE NORTHERN RED OAK BASSWOOD WOOD CUTS: TANGENTIAL – 3 MICROSCOPIC LEVEL Tangential cut  Longitudinal section (LS) not through center of stem  Longitudinal axis of vessel elements & tracheids visible; appear as long cells  Rays appear as short, vertical rows of small, round cells  Growth rings diffifult to discern WOOD CUTS: DOUGLAS FIR GROSS ANATOMICAL LEVEL TRANSVERSE RADIAL TANGENTIAL SECTION SECTION SECTION WOOD CUTS: EASTERN WHITE PINE GROSS ANATOMICAL LEVEL TRANSVERSE RADIAL TANGENTIAL SECTION SECTION SECTION WOOD CUTS: NORTHERN RED OAK GROSS ANATOMICAL LEVEL TRANSVERSE RADIAL TANGENTIAL SECTION SECTION SECTION WOOD CUTS: BASSWOOD GROSS ANATOMICAL LEVEL TRANSVERSE RADIAL TANGENTIAL SECTION SECTION SECTION