Trees and Shrubs: Definitions & Development

Flashcards reviewing key definitions, structural morphology, wood anatomy, identification traits, and development stages of trees and shrubs from lecture notes.

What is dendrology?

Dendrology is the scientific study of woody plants (trees and shrubs), with an emphasis on identification.

How is a tree defined in dendrology?

A woody plant that will grow at least $20\text{ feet}$ tall with a single primary trunk, generally unbranched for several feet, and a well-defined crown structure at maturity.

How is a shrub defined in dendrology?

A woody plant that is generally under $20\text{ feet}$ tall at maturity and has multiple stems growing from ground level.

Which plant species is specifically noted for blurring the line between trees and shrubs?

Flowering dogwood

What distinguishes gymnosperm seeds from angiosperm seeds?

Gymnosperms bear naked seeds (not enclosed in an ovary) on cones, whereas angiosperms produce seeds enclosed in ovaries with true flowers.

What type of wood do gymnosperms produce, and what are its key properties?

Gymnosperms produce softwoods, which are valued in construction due to their light weight and high strength.

Which two gymnosperm species are explicitly listed as deciduous exceptions that shed all needles annually?

Larch and baldcypress

What are cotyledons?

Cotyledons are the primary leaves of an embryo present in the seed, also known as seed leaves.

How do stem growth characteristics differ between dicots and monocots?

Dicots have vascular bundles arranged in a ring and produce annual growth rings, whereas monocots thicken stems by diffuse secondary thickening without annual growth rings.

In tree anatomy, what is the bole?

The section from the base of the trunk to the first branch, often used to describe a tree's lumber value.

How is a simple leaf distinguished from a compound leaf?

In a simple leaf, the bud is located in the axil of a single leaf and the stem; in a compound leaf, the bud is located in the axil of a structure with more than one leaflet attached.

What is the difference between odd pinnate (imparipinnate) and even pinnate (paripinnate) leaves?

Odd pinnate leaves have an odd number of leaflets, while even pinnate leaves have an even number of leaflets.

What are the three primary leaf arrangements (phyllotaxy) along a stem?

Opposite (leaves/buds directly across from each other), Alternate (spaced in alternating arrangement along the axis), and Whorled (three or more leaves/buds present at a node).

What does the mnemonic MAD CAP HORSE stand for regarding plant groups with opposite leaves?

M = maples, A = ash, D = dogwood, Cap = Family Caprifoliaceae (viburnums & honeysuckles), Horse = horsechestnuts & buckeyes.

What is the exception to the opposite leaf arrangement rule in dogwoods?

Alternate-leaf dogwood (Swida alternifolia)

What are the four main leaf venation types described in the text?

Pinnate, Arcuate (or bowed pinnate), Palmate, and Dichotomous.

What is a leaf scar?

The mark remaining after a leaf has fallen off a twig.

What is a lenticel and what is its primary function?

A small, corky spot on young bark made of loosely packed cells that allows for gas exchange between inner tissue and the atmosphere.

What is the difference between a perfect flower and an imperfect flower?

A perfect flower has both a functional stamen and pistil, while an imperfect flower lacks either a stamen or a pistil.

What is the difference between monoecious and dioecious tree species?

Monoecious species have both sexes of imperfect flowers on the same tree, whereas dioecious species have each sex confined to a separate tree.

Define the inflorescence types: raceme, umbel, and catkin.

Raceme: flowers arise from main stem, each with a pedicel; Umbel: pedicels arise from the same place at top of peduncle; Catkin: spike-like inflorescence of scaly bracts subtending imperfect flowers.

What are the four simple dry indehiscent fruit types listed in the lecture?

Achene (one-seeded fruit), Samara (usually one-seeded with a membranous wing), Nut (bony, hard, one-seeded fruit), and Nutlet (diminutive nut).

How do aggregate fruits differ from multiple fruits?

Aggregate fruits develop from a single flower containing many pistils, whereas multiple fruits consist of several flowers mostly united into one mass.

What naming suffix is shared by all plant families?

aceae

What are the four main tree development stages?

Seedling (first year of life), Sapling (small trees after first year, not sexually mature), Mature (capable of reproducing), and Senescent (declining in vigor, leading to death).

What is imbibition during seed germination?

The uptake of liquid (water) from an area of high potential (substrate) to low potential (seed), which triggers metabolic activity and splits the seed coat.

What is the difference between scarification and stratification?

Scarification is mechanical abrasion to hard, water-impervious seed coats; stratification is subjecting seeds to specific environmental conditions (temperatures, moisture, heat, or frost).

What are the three main types of tree root systems and their primary sources of stability?

Tap Root (deep root stability), Lateral Root (stability from tree weight and root spread), and Heart Root (stability from root ball weight and soil resistance).

What is the difference between excurrent and decurrent growth forms?

Excurrent growth has a dominant central leader with a conical crown (most conifers, sweetgum, yellow-poplar), while decurrent growth has spreading branches (most hardwoods).

What are the roles of xylem and phloem in vascular tissue?

Xylem (inside cambium) transports water and minerals from roots; Phloem (outside cambium) distributes nutrients produced by photosynthesis.

What are the two cell types found in xylem?

Tracheids and vessel members.

What is the difference between diffuse porous and ring porous wood?

Diffuse porous wood has slow, even vessel production throughout the season; ring porous wood forms large vessels in spring (earlywood) and smaller vessels later (latewood).

What are tyloses in oak heartwood?

Balloon-like outgrowths of parenchyma cells that bulge through the pits of vessel members and block water movement.

How do early wood and late wood differ in cellular properties?

Early wood forms during rapid spring growth with large, low-density cells having thin walls; late wood forms during slower summer growth with small, high-density cells having thick walls.

What is the difference between sensitive and complacent tree growth in dendrochronology?

Sensitive growth shows high annual variation with intermixed wide and narrow rings due to variable limiting factors; complacent growth shows low annual variation with uniform rings due to constant limiting factors.

In this diagram of a leaning tree stem, what type of reaction wood forms on the upper side of the branch in hardwoods?

Tension wood

How do tension wood and compression wood differ by plant group and location?

Tension wood forms in hardwoods on the upper side of leaning stems (lightweight, high in cellulose); compression wood forms in conifers on the lower side of leaning stems (heavy, high in lignin).

What is the functional difference between sapwood and heartwood?

Sapwood consists of lighter, younger active xylem and storage cells near bark; heartwood consists of darker, older, dead xylem near the center that no longer conducts water and contains decay-resistant compounds.

What three tissue layers make up the outer bark (periderm)?

Phellogen (cork cambium), Phelloderm (live inner layer storing starch), and Phellem (cork, outermost layer of dead cells containing suberin).

What is suberin and where is it located in bark?

Suberin is a waxy substance found in mature dead phellem (cork) cells that acts as a barrier to water loss and pathogens.

Which four pigments drive autumn leaf coloration changes?

Chlorophyll (green), Carotenoids (yellow/orange), Tannins (brown), and Anthocyanins (pink, red, purple).

What are the three distinct patterns of shoot growth in trees?

Fixed (Determinate) growth, Free (Indeterminate) growth, and Recurrent Flushing (Semi-determinate) growth.

How can a false terminal bud be distinguished from a true terminal bud?

A false terminal bud has a leaf scar at its base, whereas a true terminal bud lacks a leaf scar.