botany 2

gymnosperm

Literally means 'naked seed', referring to seeds that develop on the surface of scales or leaves without being enclosed inside a fruit.

species richness

Gymnosperms have approximately 840 extant species, while angiosperms comprise roughly 300,000 extant species.

seed plant ovule

Defined by a megasporangium (nucellus) enclosed by integuments, with a small opening known as the micropyle.

functional megaspore

In seed plants, the functional megaspore is retained inside the megasporangium and is not released into the environment.

ploidy levels of mature gymnosperm seed components

1. Seed coat: Diploid (2n) from maternal sporophyte integument; 2. Stored food supply: Haploid (1n), female gametophyte tissue; 3. Embryo: Diploid (2n), new sporophyte generation.

pollen grain

Represents the microspore that has developed into a mature male gametophyte in seed plants.

fertilization in gymnosperms

Free water is no longer required because pollen grains are transferred directly to the ovule by wind or animals.

antheridia

The male gametangial structure completely lost in gymnosperms and angiosperms.

polyembryony

The occurrence of multiple embryos within a single seed due to several archegonia produced by the megagametophyte.

sperm motility in Ginkgo/cycads vs. conifers/gnetophytes

Ginkgo and cycads produce flagellated, motile sperm; whereas conifers and gnetophytes produce non-motile sperm.

bifacial vascular cambium

Produces secondary xylem (wood) toward the inside and secondary phloem toward the outside.

Pertica varia

An early Trimerophyte that grew to about 1 m tall during the Devonian period.

Archaeopteris

Classified as a progymnosperm for producing gymnosperm-like secondary xylem (wood) and a eustele, but reproducing via spores.

seed ferns (Pteridosperms)

Represented transitional seed plants evolving from progymnosperms toward early true gymnosperms.

Cordaites

An extinct gymnosperm genus characterized by elongated leaves with secondary xylem and parallel leaf veins.

Bennettitales

An extinct Mesozoic gymnosperm group with cycad-like leaves and flower-like reproductive structures that produced oleanane.

four extant phyla of gymnosperms

1. Cycadophyta 2. Ginkgophyta 3. Coniferophyta 4. Gnetophyta.

three primary meristems from apical meristem

1. Protoderm; 2. Ground meristem; 3. Procambium.

primary tissue system from protoderm

Epidermis

primary tissue types from ground meristem

Parenchyma, collenchyma, and sclerenchyma (ground tissue system).

primary tissues from procambium

Primary xylem and primary phloem (vascular tissue system).

apical vs. lateral meristems

primary length vs secondary girth

secondary tissues from vascular cambium

Secondary xylem and secondary phloem.

protective secondary tissue from cork cambium

Periderm.

structural characteristics of parenchyma cells

Living cells with thin primary cell walls, functioning in photosynthesis and storage of sugars and starches.

structural role of collenchyma tissue

Provides flexible structural support to young stems and leaves with unevenly thickened primary cell walls.

sclerenchyma tissue at functional maturity

Sclerenchyma cells are dead and have thick, heavily lignified secondary cell walls.

tracheids vs vessel elements

Tracheids are tapered cells connected by lateral pits, while vessel elements are wider, barrel-shaped cells with perforation plates.

phloem conducting cells in angiosperms vs gymnosperms

Angiosperms have sieve-tube elements with companion cells; gymnosperms have sieve cells with albuminous cells.

palisade vs spongy mesophyll

Palisade mesophyll has columnar cells packed with chloroplasts; spongy mesophyll has loose arrangements for gas exchange.

guard cells

Specialized epidermal cells that control gas exchange and water loss through stomata.

geological period of angiosperm origin

Angiosperms originated and diversified during the Cretaceous period (145 - 65 mya).

early fossil angiosperm Archaeofructus

Dated to 125 mya, discovered in Northern China's semi-aquatic fossil beds.

notable absence in Archaeofructus perianth features

It lacks both petals and sepals.

basal angiosperm genus

Amborella represents the single sister lineage to all living flowering plants, lacking vessel elements.

cotyledon count in monocots vs eudicots

Monocots have one cotyledon; eudicots have two cotyledons.

leaf venation in monocots vs eudicots

Monocots exhibit parallel venation; eudicots display reticulate venation.

vascular bundle arrangement in monocots vs eudicots

Monocots have scattered vascular bundles; eudicots have vascular bundles in a distinct outer ring.

pollen grain aperture in eudicots

Tricolpate pollen, featuring three elongate apertures, is a defining synapomorphy for eudicots.

Asteraceae inflorescence type

Capitulum is the specialized composite inflorescence (head) of the family Asteraceae.

pappus in Asteraceae flowers

Modified calyx (sepals) reduced to bristles or scales that aid in seed dispersal.

S-RNase

Enzyme synthesized in the style during Gametophytic Self-Incompatibility that degrades RNA to block incompatible pollen tubes.

broad evolutionary trend in plant generations

Progressive reduction of the gametophyte generation and increasing dominance of the sporophyte generation from bryophytes to angiosperms.

concentric floral whorls

1. Calyx (sepals); 2. Corolla (petals); 3. Androecium (stamens); 4. Gynoecium (carpels/pistil).

tepals

Term for flower perianth parts when sepals and petals are structurally identical.

cells in mature angiosperm microgametophyte

Three cells (one tube cell and two sperm cells) prior to fertilization.

cell and nuclear count of mature angiosperm megagametophyte

Seven cells with eight nuclei (3 antipodal, 1 central with 2 polar, 2 synergid, 1 egg).

indirect pollination in angiosperms

Pollen lands on the stigma surface rather than directly on the micropyle or ovule.

first product of double fertilization

A diploid zygote (2n), formed by fusion of one haploid sperm (1n) with the haploid egg cell (1n).

tissue formed by triple fusion in double fertilization

Endosperm (3n), formed by fusion of the second haploid sperm (1n) with the two polar nuclei (1n + 1n).

seed structure from integuments post-fertilization

Seed coat is formed from the integuments of the ovule.

plant organ developed from ovary wall

Fruit develops directly from the ovary wall following fertilization in angiosperms.

female gametangial structures in gymnosperms absent in angiosperms

Archegonia are completely absent in angiosperms.

vascular bundles in pine needle cross-sections

Transfusion tissue immediately surrounds the vascular bundles inside the endodermis.

pitting pattern on secondary xylem tracheids

Pitted tracheids organized in longitudinal groups are visible in progymnosperms like Archaeopteris.