Plant Secondary Growth – Vocabulary Review

32 vocabulary flashcards covering major terms and concepts from the lecture on plant secondary growth, including cambial activity, tissue types, division patterns, and special cases in monocots.

Primary Growth

Increase in length of roots and shoots produced by activity of the apical meristems and their three primary meristems (dermal, ground, vascular).

Secondary Growth

Increase in girth (thickening) of stems and roots produced mainly by the vascular cambium (and cork cambium); characteristic of woody plants.

Vascular Cambium

A secondary meristem that produces secondary xylem inward and secondary phloem outward, driving most secondary growth.

Secondary Xylem

Wood; water-conducting tissue formed to the inside of the vascular cambium each year or growth period.

Secondary Phloem

Food-conducting tissue formed to the outside of the vascular cambium during secondary growth.

Fusiform Initials

Elongated vascular-cambium cells that divide to produce the axial (vertical) conductive cells of secondary xylem and phloem.

Ray Initials

Rounded vascular-cambium cells that generate radial rows of parenchyma called rays, running from xylem through cambium to phloem.

Periclinal Division

Cell division in the cambium parallel to the stem surface, adding xylem inward and phloem outward.

Anticlinal Division

Cell division in the cambium perpendicular to the stem surface, expanding the circumference of the cambial ring.

Procambium

Primary meristem within vascular bundles that can retain meristematic activity and become part of the vascular cambium.

Protostele

A solid core of vascular tissue common in young roots, with xylem in the center and phloem between its arms.

Eustele

Stem stele type with discrete vascular bundles arranged in a ring, typical of seed-plant stems before secondary growth begins.

Fascicular Cambium

Portion of the vascular cambium that develops inside an original vascular bundle.

Interfascicular Cambium

Cambial tissue that forms between vascular bundles, completing the continuous cambial ring in stems.

Periderm

Protective tissue replacing the epidermis during secondary growth; consists of cork cambium, cork (phellem), and phelloderm.

Cork Cambium (Phellogen)

Secondary meristem that produces cork cells to the outside and phelloderm to the inside, forming the periderm.

Cork (Phellem)

Suberized, dead cells produced outward by the cork cambium; main component of bark’s outer layers.

Phelloderm

Living parenchyma cells produced inward by the cork cambium as part of the periderm.

Bark

Collective term for all tissues external to the vascular cambium: secondary phloem plus periderm layers.

Annual Ring

Visible ring of secondary xylem produced during one growth season; results from contrast between earlywood and latewood.

Earlywood

Portion of an annual ring formed at the start of the growing season; usually has larger, thinner-walled vessels or tracheids.

Latewood

Denser portion of an annual ring formed later in the season; cells are smaller and thicker-walled than in earlywood.

Lignophyte

Seed plant lineage characterized by possession of a vascular cambium and wood; ancestral state for seed plants.

Herbaceous Plant

Plant lacking significant secondary growth; stems remain soft, green, and non-woody.

Pericycle

Layer just inside the endodermis of roots; contributes to formation of the vascular cambium and lateral roots.

Phloem Fibers

Tough, supportive sclerenchyma fibers often capping primary phloem; visible markers of original phloem position after secondary growth.

Tangential Section

Longitudinal cut tangent to the circumference of wood, exposing axial cells in face view and rays as ends.

Radial Section

Longitudinal cut along a radius of the stem, showing rays as continuous bands and axial elements in side view.

Transverse Section

Cross-section cut perpendicular to the stem axis, revealing growth rings and circular arrangement of tissues.

Massive Primary Thickening (Palms)

Stem enlargement in some monocots (e.g., palms) produced by a broad primary meristem, not by a vascular cambium.

Cambial Zone (Cabbage Tree)

Multiple concentric meristematic layers in certain monocots that produce unusual secondary growth and spongy wood.