Chapter 1: Tree Biology Flashcards
meristems
undifferentiated tissue in which active cell division takes place. Found in the root tips, buds, cambium, cork cambium, and latent buds.
differentiation
process in the development of cells in which they become specialized for various functions. Following division, cells change their structure assume a variety of special functions.
5 organs of plants
leaves, stems, roots, flowers, and fruit
primary meristems
produce the cells that result in elongation of shoots and roots
secondary meristems
lateral meristems; produce cells that result in increases in diameter
primary growth
root and stem growth in length. Occurs at the apical meristems and lateral meristems of all vascular plants
secondary growth
increase in root and stem girth or diameter. Occurs at lateral meristems in some vascular plants such as dicots
apical bud
bud at the tip of a twig or shoot
bud
small lateral or terminal protuberance on the stem of a plant that may develop into a flower or shoot. Undeveloped flower or shoot containing a meristematic growing point.
root cap
protects the apical meristem in roots
cambium
thin layer(s) of meristematic cells that give rise to the vascular system of the tree. Outward - to the phloem; Inward - to the xylem, increasing stem and root diameter
2 kinds of tissues that the cambium produces
xylem and phloem
xylem
main water-conducting and mineral-conducting (unidirectional, up only) tissue in trees and other plants. Provides structural support. Arises (inward) from the cambium and becomes wood after lignifying. Wood of the tree.
phloem
plant vascular tissue that transports photosynthates and growth regulators. Situated on the inside of the bark, just outside the cambium. (Bidirectional, transports up and down.) Slow movement of carbohydrates (sugars) along pressure gradients, which require energy.
cork cambium
meristematic tissue from which the corky, protective outer layer of bark is formed
periderm
the outer layers of tissue of woody roots and stems, consisting of the cork cambium and the tissues produced by it, such as bark.
cellulose
structural component of the cell wall; complex carbohydrate found in the cellular walls of the majority of plants and algae and certain fungi.
most common organic compound on Earth
cellulose
lignin
organic substance that impregnates certain cell walls to thicken and strengthen the cell to reduce susceptibility to decay and pest damage; provides strength and rigidity allowing trees to grow tall.
4 primary functions of the xylem
- ) conduction of water and dissolved minerals (elements)
- ) support of the weight of the tree
- ) storage of carbohydrate reserves
- ) defense against the spread of disease and decay
carbohydrate
compound, combining carbon, hydrogen, and oxygen, that is produced by plants as a result of photosynthesis. Sugars and starches. Chains of carbon, hydrogen, and oxygen molecules chemically bonded together.
symplasm
living tissue of the tree; entire mass of protoplasm of all the cells in a plant, interconnected by plasmodesmata. Symplast.
apoplasm
nonliving tissue of the tree; free spaces in plant tissue. Includes cell walls and intracellular spaces.
tracheids
elongated, dead cells with pointy ends and thickened walls that conduct water and provide mechanical support; elongated, tapering xylem cell adapted for the support and transport of water and elements.
parenchyma cells
living cells interspersed among other xylem cells; located in the outer layers of xylem; store carbohydrates, help defend against decay, and have a structural function across the grain; thin-walled, living cells essential in photosynthesis, radial transport, energy storage, and production of protective compounds.
components of the xylem in hardwood trees
tracheids, fibers, parenchyma cells, and vessels
vessels
primary conducting elements in hardwoods; stacks of dead, hollow cells that form long tubes of water-conducting elements; more efficient in water conduction than tracheids; end-to-end, tube-like, water-conducting cells in the xylem of angiosperms
ring porous
species that form wide vessels early in the growing season and narrower vessels later in the season; pattern of wood development in which the large-diameter vessels are concentrated in the earlywood.
Examples of ring porous species
Elm (Ulmus)
Oak (Quercus)
Ash (Fraxinus)
diffuse porous
species that produce vessels of uniform size throughout the growing season; pattern of wood development in which the vessels and vessel sizes are distributed evenly throughout the annual ring.
Examples of diffuse porous species
Maple (Acer)
Planetree (Platanus)
Poplar (Populus)
growth rings
rings of xylem that are visible in a cross section of the stem, branches, and roots of some trees. In temperate zones, the rings typically represent one year of growth and are sometimes referred to as annual rings. Result of seasonal production of xylem by the cambium.
earlywood
cells produced early in the season
latewood
cells produced later in the season
sapwood
xylem that conducts water; outer wood that is active in longitudinal transport of water and minerals; contains many living parenchyma cells
heartwood
nonconducting tissue that contains no living cells and is sometimes darker in color than the sapwood; wood that is altered (inward) from sapwood and provides chemical defense against decay-causing organisms and continues to provide structural strength to the trunk; not all trees have it
sieve cells
long, slender phloem cell in gymnosperms
sieve tube elements
specialized phloem cells involved in photosynthate transport; exist only in angiosperms
companion cells
specialized cell in the angiosperm phloem derived from the same parent cell as the closely associated, immediately adjacent sieve-tube member
components of functional phloem
living cells: sieve cells in conifers; sieve tube elements and companion cells in hardwoods
rays
parenchyma cells that extend radially across the xylem and phloem of a tree and function in transport, storage, structural strength, and defense; parenchyma cells that grow radially across the grain in small layers that extend across the growth increments of xylem and into the phloem; transport carbohydrates and other compounds into sapwood, store carbohydrates as starch, and assist in restricting decay in wood tissue.
bark
the outer covering of a tree’s branches, stems, and in some cases, roots
composition and purpose of bark
composed of protective tissues that moderate the temperature inside the stem, offer defense against injury, and reduce water loss
lenticle
small opening in the bark that permits the exchange of gases
twigs
small stems that provide support structure for leaves, flowers, and fruit
apical bud
bud at the tip of a twig or shoot; terminal bud
terminal bud
bud at the tip of a twig or shoot
lateral bud
vegetative bud on the side of a stem
axillary bud
bud in the axil of a leaf; lateral bud
dormant
in a period of dormancy
apical dominance
condition in which the terminal bud inhibits the growth and development of the lateral buds on the same stem/shoot formed during the same season
adventitious bud
bud arising from a place other than a leaf axil or shoot tip, usually as a result of hormonal triggers; produced along stems or roots where primary meristems are not normally found
epicormic
arising from a latent adventitious bud (growth point), usually in reference to a shoot; shoots that are produced from elongated dormant buds
node
slightly enlarged portion of the stem/twig where leaves and buds arise
internode
region of the stem between two successive nodes; area between nodes
autonomous
producing and storing enough carbohydrates to sustain itself
branch collar
area where a branch joins another branch or trunk that is created by the overlapping vascular tissues from both the branch and the trunk; typically enlarged at the base of the branch; annual production of layers of tissue at the junction of the branch to the stem, seen as a shoulder or bulge around the branch base
branch bark ridge
raised strip of bark at the top of a branch union, where the growth and expansion of the trunk or parent stem and adjoining branch push the bark into a ridge
included bark
bark that becomes embedded in a crotch (union) between branch and trunk or between codominant stems; causes a weak structure
food producers of the tree
leaves
chloroplasts
specialized organelle found in some cells; site of photosynthesis
chlorophyll
green pigment of plants found in chloroplasts; captures the energy of the sun and is essential in photosynthesis
photosynethsis
process in green plants (and in algae and some bacteria) by which light energy is used to form glucose (chemical energy) from water and carbon dioxide
transpiration
water vapor loss through the stomata of leaves; loss of water through the foliage in the form of water vapor, which helps cool the leaf and draw water up through the xylem
cuticle
waxy layer outside the epidermis of a leaf that reduces water loss and resists insect damage; minimizes desiccation (drying out) of the leaf
stomata
small pores, between two guard cells on the undersides of leaves and other green plant parts, through which gases are exchanged and water loss is regulated
guard cells
pair of specialized cells that regulate the opening and closing of a stomate due to a change in pressure within cells or in response to environmental stimuli such as light, temperature, and humidity
deciduous
tree or other plant that sheds all of its leaves according to a genetically scheduled cycle as impacted by climate factors (usually during the cold season in temperate zones); trees that lose their leaves in response to periodic environmental changes, such as day length, temperature, and/or rainfall
evergreen
tree or other plant that does not shed all of its foliage annually
abscission zone
area at the base of the petiole where cellular breakdown leads to leaf and fruit drop; cell changes and growth regulators combine to form this during the periodic environmental changes that cause leaves to fall
petiole
stalk or support axis of a leaf
2 functions of the abscission zone
- ) to enable leaf drop
2. ) to protect the region of the stem from which the leaf has fallen against desiccation and pathogen entry
What causes fall foliage color in deciduous trees?
Breakdown of chlorophyll in the leaf; short sunny days combined with cold nights enhance the accumulation of sugars and trigger a decrease in chlorophyll production; process allows other pigments to be unmasked
anthocyanins
red or purple pigment responsible for those colors in some parts of trees and other plants.
carotenoids
yellow, orange, or red pigment responsible for those colors in some parts of trees and other plants
4 primary functions of roots
- ) anchorage
- ) storage
- ) absorption
- ) conduction
main functions of large roots
anchorage, storage, and conduction
absorbing roots
small, fine, fibrous, primary tissues that grow at the ends of and along the main, woody roots, which aid in the uptake of water and minerals; have epidermal cells that may be modified into root hairs; contain a meristematic zone where the cells divide and elongate; found in the upper 6 to 10 inches of soil
Where do most absorbing roots occur?
Within the top 12 inches (30 cm) of soil; [few roots grow deeper than 3 to 4 feet (depending on tree species and environmental conditions, it is possible to develop much deeper root systems)]
lateral root
root that arises by cell division in the pericycle of the parent root and then penetrates the cortex and epidermis
Where do most horizontal lateral roots occur?
Near the soil surface.
sinker roots
downward-growing roots that provide anchorage and take up water and minerals; especially useful during periods of drought; increases the depth of soil exploited by the root system
tap root
central, vertical root growing directly below the main stem or trunk that may not persist into plant maturity
Why do few mature trees have tap roots?
Because it usually gets choked out by the expansion of roots around it or is diverted from its downward growth by unfavorable growing conditions
root crown
area where the main roots join the plant main stem, usually at or near ground level; root collar
zone of rapid taper
area outside of the root crown where the roots spread out and decrease rather quickly in diameter to long, spreading, branching roots, 1 to 2 inches in diamter
How far do roots extend laterally?
Depends on the tree and soil conditions; may be considerable distances; often two to three times the radius of the crown; the extent and direction of root growth is more of a function of environment than genetics
mycorrhizae
symbiotic association between certain fungi and the roots of a plant; fungus roots
symbiosis
association of two different types of living organisms that is often, but not always, beneficial to each; both tree and fungus in this case benefit from the living arrangement
Symbiotic relationship between fungi and tree
Fungi derive nourishment from the roots of the tree; fungi aid the roots in absorption of water and essential mineral elements
photosynthate
general term for the sugars and other carbohydrates produced during photosynthesis; the building blocks for many other compounds required by the plant
How is most of photosynthate stored in the tree?
In the form of starch, for later energy requirements
respiration
in plants, process by which carbohydrates (generated by photosynthesis) are converted into energy by using oxygen
transpirational pull
created by evaporation of water and cooling of leaves during transpiration, which moves water up through the xylem
What effects the rate of transpiration?
temperature, humidity, and available water; also affected by anatomical features such as cuticle thickness, presence of hairs on the leaf surface, and the number and location of stomata.
antitranspirant
substance applied to the foliage of plants to reduce water loss (transpiration) by closing stomatal pores artificially or adding impervious coating on the leaf surface, thus reducing water loss during transplanting or under drought conditions
Pros and Cons of antitranspirant sprays
Pro: reduces water loss during transplanting or under drought conditions
Con: reduces evaporative cooling of leaves, reduces update of carbon dioxide, reducing photosynthesis
What forces contribute to the mass movement of water in the xylem?
Transpirational pull in the xylem (xylem can be thought of as a continuous column of water, where evaporation of water molecules from the leaves pulls water up through the tree), adhesion, cohesion, and pressure differentials
osmosis
diffusion of water through a semi-permeable membrane from a region of higher water potential (lower salt concentration) to a region of lower water potential (higher salt concentration).
What has the highest potential? (In osmosis)
Pure water. Adding anything such as minerals or sugars lowers the potential.
angiosperms
plant with seeds born in an ovary. Consists of two large groups: Monocotyledons (grasses, palms, and related plants) and dicotyledons (most woody trees, shrubs, herbaceous plants, and related plants)
source
in physiology, plant part that produces carbohydrates, such as mature leaves
sink
plant part that uses or stores more energy than it produces, such as young leaves
axial transport
movement of water, minerals, or photosynthates longitudinally within a tree
radial transport
lateral movement of substances, perpendicular to the longitudinal axis of the tree or stem
plant growth regulators
compound effective in small quantities that affects the growth and/or development of plants; may be naturally produced (hormone) or synthetic
plant hormone
substance produced by a plant that, in low concentrations, affects physiological processes such as growth and development, often at a distance from the substance point of origin
major hormone groups
auxins, gibberellins, cytokinins, ethylene, and abscissic acid
What do plant growth substances control?
Functions such as cell division, cell elongation, flowering, fruit ripening, leaf drop, dormancy, and root development
auxin
plant hormone or substance that promotes or regulates the growth and development of plants. Produced at sites where cells are dividing, primarily in shoot tips, but also important in root development. Auxin-like compounds may be synthetically produced to enhance rooting of cuttings and also as herbicides.
cytokinins
plant hormone involved in cell division, leaf expansion, and other physiological processes. Compounds with cytokinin-like activity may be synthetically produced. Instrumental in shoot initiation and growth.
tropisms
tendency of growth or variation of a plant in response to an external stimulus such as gravity (geotropism) or light (phototropism); orientation of the direction of growth in response to an external stimulus.
geotropism
plant growth produced as a response to the force of gravity, either positive, as in the direction of gravity (roots), or negative, as in opposite the direction of gravity (shoots)
phototropism
influence of light on the direction of plant growth. Tendency of plants to grow toward light.
How is apical dominance a result of plant growth regulators?
Growth regulators present in terminal buds inhibit the growth and development of lateral buds on the same shoot. Strong dominance is confined primarily to the current season’s shoot growth. During the following season lateral buds start growing.
Decurrent
rounded or spreading growth habit of the tree crown; when new lateral shoots outgrow the original terminal shoot year after year
Excurrent
tree growth habit characterized by a central leader and pyramidal crown; upright trees with strong central leaders due to strong apical control
Features that serve as protection
thick bark, thorns, leaf hairs, thick cuticles, and more. Cellular materials may resist decay or may be indigestible by insects, production of chemicals that resist insect feeding, pathogen infection, or decay.
Compartmentalization
natural defense process in trees by which chemical and physical boundaries are created that act to limit the spread of disease and decay organisms
CODIT
Compartmentalization Of Decay In Trees - trees form four barrier walls. Wall 1, resists vertical spread; Wall 2, resists inward spread; Wall 3, inhibits lateral spread; Wall 4, protects against outward spread of decay
Wall 1 (CODIT)
resists vertical spread by plugging xylem vessels
Wall 2 (CODIT)
resist inward spread by the more compact latewood cells and by depositing chemicals in these cells
Wall 3 (CODIT)
inhibits lateral spread by activating ray cells to resist decay
reaction zone
natural boundary formed chemically within a tree to separate damaged wood from existing healthy wood. Important in the process of compartmentalization. Walls 1-3 form this.
Wall 4 (CODIT)
next layer of wood to form after injury (new wood tissue); protects against the outward spread of decay
Rank the CODIT walls from weakest to strongest
Wall 1 is the weakest and Wall 4 is the strongest against decay. If Walls 1, 2, and 3 fail the tree will allow decay to spread inside the tree, forming a hollow cavity. Wall 4 fails less commonly.
temperate
region lying between the tropics and the poles that has relatively moderate temperatures (opposite of tropical trees)
tropical trees
lack “annual” growth rings, because growth is more or less continuous or highly regulated by dry and wet seasons
buttress roots
roots at the trunk base that help support the tree and distribute/equalize mechanical stress
aerial roots
aboveground roots, usually adventitious in nature and sometimes having unique adaptive functions
Functions of aerial roots
support (serving as props), gas exchange, and propagation
propagation
process of increasing plant numbers, both sexually and asexually (new plants produced in this way are clones of the parent tree)
Who tends to have faster growth between tropical and temperate species?
Tropical - because of favorable growing conditions in tropical climates; these favorable conditions have a “forgiving” effect which aids in ease of transplanting, would closure, and regrowth after injury
ecology
study of the relationships among organisms and other living and nonliving elements of their environment
monocots
monocotyledon; plant with an embryo that has one seed leaf (cotyledon); grasses and palms
fronds
large, divided leaf structures found in palms and ferns; where photosynthesis takes place; dominate the palm crown; leaves of palms consisting of a blade, a petiole, and a leaf base
palm’s establishment period
the number and size of vascular bundles increases; attain maximum girth during this stage, mostly prior to beginning vertical elongation of the stem
The largest leaves of any trees belong to?
Palms; growing up to 60 ft long in some species; vary greatly in color, form, features, and thickness
leaf axils
point of attachment of a leaf petiole to a stem
inflorescences
cluster of (many individual) flowers
root initiation zone
region at the base of a palm stem where lateral roots emerge
root mat
dense network of roots near the base of a palm; found in the upper 12 to 18 inches of the soil and close to the stem; portion may be above ground; do not form mycorrhizal associations
