What is a TREE? Woody plant (stems, branches, roots) Long lived (typically 100 s of yrs. sometimes 10

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Scarlett Carroll
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variability) Annual height AND diameter growth (woody plants have 3 meristems) Ability to compartmentalize

1 What is a TREE? Woody plant (stems, branches, roots) Long lived (typically 100 s of yrs. sometimes 10 s or 1000 s) Single main axis (stem, trunk, bole) Typically tall at maturity (note variability) Annual height AND diameter growth (woody plants have 3 meristems) Ability to compartmentalize problems Not everything called a tree meets this definition How many species? Perhaps 8-10,000 Depends on definition and interpretation

2 But what about these?

3 Systems and Organs 3 systems: Dermal: skin Vascular: circulatory system Fundamental: structural (skeletal) 6 organs: Vegetative: leaves, shoots, roots Reproductive: flowers, fruits, seeds

4 3 parts of a leaf: blade, petiole, stipules Blade Simple Compound/multiple compound Petiole Petiolate Sessile Stipules Often absent Common in tropical plants Structure of Leaves

5 STRUCTURE OF A BROADLEAF LEAF Dermal System: cuticle, epidermis, stomata, guard cells Vascular System: xylem, phloem, bundle sheath Structural System: mesophyll, pith (includes the various enchyma cells)

6 Leaf stoma, guard cells, stomatal bloom

7 Cross Section of Pine Needle

8 Sun/shade leaves in western hemlock Leaf Variation Snowberry and canyon live oak

9 Structure of woody stems Function Support Conduction Storage Form Tapering columns of annual sheaths Similar to stacking cones except for connectivity between rings and around branches Annual growth rings (on trunk and branches)

10 Internal structure of a tree Outer bark Inner bark Vascular cambium Sapwood Heartwood (can t see pith)

11 How Do Trees Work? Wood (xylem) Sapwood (conductive) Young xylem Heartwood (non-conductive, structural) Older xylem Vascular Cambium Thin layer of cells Produces xylem (to the inside) and phloem (to the outside) Bark Inner bark (conductive) Includes phloem and cortex Outer bark (protective) Cork cambium Produces cortex (to the inside) and cork (to the outside)

Earlywood Latewood (Springwood Summerwood) Occurs within a single annual ring Occurs because earlywood cells are thin walled (light in color) and latewood cells are thick walled (darker in color)

12 Earlywood Latewood (Springwood Summerwood) Occurs within a single annual ring Occurs because earlywood cells are thin walled (light in color) and latewood cells are thick walled (darker in color) Very distinct in some trees, not in others Wood properties are affected by rate of diameter growth Slow growth results in tight rings and high wood quality Fast growth results in wider rings and sometimes problems

13 Not all cross sections look the same

15 Burls and Lignotubers

16 Bark: complex structure with many layers

17 cork oak Quercus suber

18 Variations in Bark

19 Special properties of bark Inert (non-reactive) Insulating Non-porous to liquids and gasses Example: corkbark oak from Spain and Portugal

Roots Many depictions of roots mostly wrong Function Anchorage Absorption Storage (food and extractives) Primary roots Trace origin to radicle

21 Roots Many depictions of roots mostly wrong Function Anchorage Absorption Storage (food and extractives) Primary roots Trace origin to radicle Taproots (many misconceptions) Adventitious roots Arise from phloem parenchyma (unpredictable pattern) Help trees adapt to changing conditions (e.g. redwoods)

22 Typical root tip Root Structure Mycorrhizal infected root tip

23 Some special adaptations of roots Prop roots: adventitious roots that help support the plant Pneumataphores: aerial roots that help plants breath in poorly aerated soils

24 Some special adaptations of roots Buttressed roots: help stabilize the tree Aerial roots:

25 Some special adaptations of roots Nodulated roots: fix atmospheric nitrogen and convert it to a form plants can use. Mycorrhizal roots: fungus-root association. Tree feeds fungus but benefits by increased uptake of water and nutrients.

26 Some special adaptations of roots Strangler figs: germinate in tree top and send roots down to ground may kill host

27 Special Adaptations of Roots

Root Trivia Spread laterally well beyond crown width Most roots lie within 12-18 of soil surface, even when soils are deep This is why compaction is such a problem Western soils are shallow, so roots

28 Root Trivia Spread laterally well beyond crown width Most roots lie within of soil surface, even when soils are deep This is why compaction is such a problem Western soils are shallow, so roots are shallow Plants in dry climates have/need more roots than plants in moist climates Root systems require large inputs of energy to maintain themselves and are importnat in nutrient cycling Fine roots don t live long (weeks to months) Root grafts allow trees to share resources, but also diseases (argues against same species urban plantings) In PNW, fall is prime root growing time (before winter cold and summer drought) Living roots are white; dead roots are brown Mature oak trees may have 500 million living root tips

29 Vegetative Growth Growth occurs in cycles seasonal, annual, over life span Growth is centered in meristems lateral and apical. Growth occurs in spurts it s not continuous even within a season.

30 Shoot Elongation Results in taller trees and longer branches (wider crowns) Originates from buds Terminal Lateral Adventitious Develop in unpredictable pattern Buds result in: Vegetative growth Reproductive growth Mixed States of activity: Active Dormant common at root collar Activated when environment changes

31 Adventitious and Dormant Buds

32 Leaf Growth Individual leaves Broadleaves may take 2-40 days to develop Conifer leaves take longer Some add weight throughout their lives Whole plants Some develop all leaves early in season Some add leaves throughout season Deciduous leaves Last one growing season (ended by cold or drought) Sometimes multiple growing seasons w/in single year Leaf fall is programmed nutrients are reculceld Abscission layer forms Evergreen leaves Don t last forever Highly variable by species

33 Shoot growth Characterized by: Characterized by: Location terminal, lateral, basal, water shoots Type of bud Coppice (from root collar) Epicormic (from advnetitious buds on stem Determinate: Occurs from true terminal buds Typically only 1 flush/yr., but some are recurrent Most pines, spruces, oaks, hickories Indeterminate No terminal bud is set winter die back occurs to hardened bud Birches, sycamores, locusts, basswood, hawthrons

34 Shoot Growth Fixed vs. Free Growth Fixed: Predetermined growth based on previous growing season Examples: Dougals-fir, hemlocks, spruces, firs Free growth No predetrmination Growth continues based on growing season Examples: poplars, apples, larches, tropical pines Abnormal Shoot Growth Recurrent flushing Multiple flushes w/in 1 season Common in sub-tropical and tropical species Difficult to count rings, affects wood quality, may result in winter damage if planted too far north Abnormal late season flushes Lammas growth if terminal Prolecptic growth if lateral Often results in winter damage

35 Shoot Growth w/in a single tree Apical dominance Pattern is determined within a single growing season Pattern is controlled by auxin, a growth hormone Strong dominance: terminal shoot elongates more than laterals Examples: Douglas-fir, true firs, spruces Weak dominance: laterals may elongate as much as or more than terminals Examples: western hemlock, knobcone pine, many broadleaved trees.

36 All trees have a maximum height (more or less) Regardless of light, water, and nutrients they receive Determined by genetics Not much influence by growth rate or longevity Some trees that grow rapidly are short lived Some that grow very slowly are very long-lived Some do both Maximum height

CAMBIUM, meristem, heartwood, and lenticel are

Examining the Structures of a Tree CAMBIUM, meristem, heartwood, and lenticel are some terms that may be new to you. These terms are used to describe various tree structures. Not surprisingly, many terms