trees pls44

Primary growth

Increase in length of stems and roots, driven by apical meristems.

Secondary growth

Increase in girth due to vascular and cork cambia activity.

Apical meristem

Meristematic tissue at root and shoot tips responsible for elongation.

Lateral meristem

Secondary meristems (vascular and cork cambia) that thicken stems and roots.

Vascular cambium

Produces secondary xylem (wood) inward and secondary phloem outward.

Cork cambium

Produces cork cells for bark protection.

Cell division, enlargement, differentiation

Three stages of plant growth: multiplying, expanding, and specializing cells.

Bud initiation and break

Formation and sprouting of buds, linked to seasonal cycles.

Epicormic shoots

Shoots from dormant buds under bark, activated by stress/pruning.

Phenology

Study of seasonal biological events like budburst, leafing, flowering, senescence.

Growth rings (annual rings)

Layers of xylem formed yearly, indicators of age and climate.

False rings

Incomplete or extra rings caused by stress/weather.

Earlywood / Latewood

Earlywood: large, thin-walled cells formed in spring. Latewood: dense, small cells formed later.

Juvenile wood

Early wood near the pith, often weaker and less dense.

Mature wood

Later-formed wood with more stable properties.

Tree crown

The leafy portion of a tree, often classified as dominant, co-dominant, intermediate, or suppressed.

Crown shape

Overall form of the crown (round, conical, spreading, etc.).

Branch phyllotaxis

Arrangement of branches/leaves: spiral, opposite, or whorled.

Branch order

Hierarchical branching: primary, secondary, tertiary, etc.

Apical dominance

Suppression of lateral buds by hormones (auxin) from the terminal bud.

Apical control

Regulation of overall vertical dominance of the main axis.

Monopodial branching

Persistent growth from a main axis (common in conifers).

Sympodial branching

Main axis terminates, and growth continues via lateral branches (common in angiosperms).

Sylleptic branching

Branches develop directly without a resting bud stage (continuous, same year).

Proleptic branching

Branches arise from buds that rested before elongating (delayed growth).

Tree habit

Growth form: excurrent (single trunk, conical; e.g., pine) or decurrent (spreading; e.g., oak).

Root architecture

Arrangement of roots: taproot, lateral roots, adventitious roots, buttress roots.

Canopy layering

Vertical stratification of foliage layers in forests.

Xylem

Water-conducting tissue of tracheids, vessels, fibers, parenchyma.

Phloem

Sugar-conducting tissue with sieve tubes, companion cells, parenchyma.

Tracheids

Narrow, elongated water-conducting cells (main in conifers).

Vessels

Wider, shorter conducting cells forming tubes (in angiosperms).

Rays

Radial parenchyma transporting substances laterally.

Pith

Central parenchyma core in young stems.

Bark

Protective outer covering: phloem, cork cambium, cork, rhytidome.

Heartwood

Inner, non-living xylem, often darker, resistant to decay.

Sapwood

Outer xylem actively conducting water.

Reaction wood

Specialized wood formed under stress: compression wood (conifers) or tension wood (angiosperms).

Lenticels

Small bark openings for gas exchange.

Resin canals

Tubes in conifers producing resin for defense.

Transpiration stream

Flow of water from roots to leaves, driven by evaporation.

Water potential gradient

Force driving water movement in plants.

Photosynthate transport

Movement of sugars from sources (leaves) to sinks (roots, fruits).

Source–sink relationship

Dynamic allocation of sugars depending on demand.

Hydraulic conductivity

Efficiency of water transport through xylem.

Cavitation

Formation of air bubbles blocking water transport.

Non-structural carbohydrates (NSCs)

Sugars and starch stored for metabolism and stress survival.

Carbon allocation

Partitioning of carbon among growth, storage, reproduction, defense.

Secondary thickening

Stem/root girth increase via cambial activity.

Dendrochronology

Tree-ring study for age and climate history.

Leaf area index (LAI)

Ratio of leaf surface area to ground area.

Self-pruning

Natural shedding of shaded/lower branches.

Crown shyness

Gaps where adjacent crowns avoid overlapping.

Root–shoot ratio

Biomass proportion between below- and aboveground tissues.

Root collar

Transition between root system and stem base.

Tree buttress

Flared basal roots supporting tall trees (common in tropics).

Axillary bud

Bud formed in the leaf axil (angle).

Adventitious roots

Roots arising from stems, branches, or leaves.

Growth flushes

Cyclic bursts of shoot elongation (polycyclic: multiple per year; monocyclic: one per year).

Epicormic buds

Dormant buds beneath bark that sprout after stress/damage.

Lignotuber

Woody swelling at base storing buds and carbohydrates for resprouting.