Biology F+F Glossary - Weeks 1-5

Microphyll

Small leaf with a single strand of vascular tissue; the early/primitive leaf form found in lycophytes (club mosses, spike mosses, quillworts)

Megaphyll

Larger leaf with a highly branched vascular system; the more evolved leaf form present in all other vascular plants

Sporophyll

A specialised leaf that bears sporangia, which give rise to spores

Strobili

Cone-like structures formed by specialised sporophylls in gymnosperms

Homosporous

Having one type of sporophyll bearing one type of sporangium, producing one type of spore that typically develops into a bisexual gametophyte (e.g. ferns)

Heterosporous

Having two types of sporophylls (micro- and megasporophylls), producing two types of spores that develop into separate male and female gametophytes (all seed plants)

Megasporophyll

A sporophyll bearing megasporangia, which give rise to megaspores, which develop into female gametophytes that produce eggs

Microsporophyll

A sporophyll bearing microsporangia, which give rise to microspores, which develop into male gametophytes that produce sperm

Gymnosperm

A vascular plant that bears naked seeds, not enclosed in a protective chamber

Angiosperm

A vascular plant that bears flowers, forming seeds inside a protective chamber

Pollen

A structure in seed plants consisting of the male gametophyte enclosed within a pollen wall

Ovule

A structure that develops within the ovary of a seed plant and contains the female gametophyte

Seed

An embryo packaged with a stored food supply, within a protective coat

Plant embryo

Contains the earliest forms of a plant's roots, stem and leaves; develops after fertilisation

What does an ovule consist of?

Megasporangium + megaspore + integument

Three key advantages of seeds over spores

Multicellular embryo with protective coat, long dormancy period (vs short spore lifespan), and a stored food supply

Why don't gymnosperms and angiosperms need water for fertilisation?

Sperm is delivered via a pollen tube (wind- or animal-carried pollen), not free-swimming flagellated sperm like in mosses

Embryophytes

The name for all plants, reflecting the significant derived trait of a multicellular, dependent embryo

Ovulate cone

The large female gymnosperm cone, made of megaphyll and stem tissue, with multiple cone scales each bearing two ovules

Pollen cone

The small male gymnosperm cone containing multiple microsporangia that produce pollen via meiosis

In gymnosperms, how long after pollen germination does fertilisation typically occur?

At least 12 months (the whole process can take around 3 years)

What is unusual about Cycad sperm?

Cycads have flagellated (swimming) sperm, indicating descent from seedless vascular plants

Huon Pine

A gymnosperm conifer (Araucariaceae, not a true pine) with high oil content (methyl eugenol) resisting water/insects; some individuals over 3,000 years old

Bunya Bunya Pine

A gymnosperm conifer producing large edible cones; considered sacred by the Gubbi Gubbi people as a ceremonial food source

Anthophyta

The single phylum containing all angiosperms (~250,000 species, ~90% of all plant species)

Sepals

Floral organ that protects the bud

Petals

Floral organ that attracts pollinators

Carpel — 3 parts

Stigma (pollen lands here), style (pollen tube grows through here), ovary (contains ovules)

Stamen — 2 parts

Anther (contains pollen grains) and filament (supports the anther)

Gynoecium

The collective term for all the carpels of a flower

Self-pollination

Pollen from the same plant lands on its own stigma

Cross-pollination

Pollen from a different plant lands on the stigma

Double fertilisation

A process unique to angiosperms: one sperm fertilises the egg (forming a 2n zygote), the other sperm fuses with two polar nuclei (forming 3n endosperm)

Ploidy of the angiosperm zygote

2n (diploid)

Ploidy of angiosperm endosperm

3n (triploid)

How do flowers prevent polyspermy?

Ovules release attracting chemicals that guide pollen tubes; extracellular signalling prevents additional pollen tubes entering the ovule once one succeeds (fastest tube wins)

Micropyle

The opening in the ovule's integuments through which the pollen tube enters

Embryo sac contents

3 antipodal cells, 2 synergids, 1 central cell, and the egg cell

Fruit

The mature ovary of a flower; protects seeds and aids their dispersal

Fleshy fruit

Fruit where the ovary wall (pericarp) becomes soft during ripening (e.g. grapes, tomatoes, cherries)

Dry fruit

Fruit with a hard, dry pericarp (e.g. beans, nuts, grains)

Are cereal grains (corn, rice, wheat) seeds or fruits?

Fruits — the hard covering is the former ovary wall fused to the seed coat

When did angiosperms first appear and dominate ecosystems?

Emerged ~140 million years ago; dominated terrestrial ecosystems by ~100 million years ago

What major evolutionary event coincided with angiosperm dominance?

The extinction of the dinosaurs (~66 million years ago)

What is thought to be the major driver of seeded plant success?

The reduction in gametophyte size over evolutionary time (shift from gametophyte to sporophyte dominance)

Monocot cotyledon number

One

Eudicot cotyledon number

Two

Monocot leaf veins

Parallel

Eudicot leaf veins

Network/branched

Monocot root system

Fibrous root network

Eudicot root system

Tap root with lateral roots

Monocot pollen type

Monosulcate

Eudicot pollen type

Trisulcate

Monocot flower parts

Three, or multiples of three

Eudicot flower parts

Four or five, or multiples of four/five

What is unusual about water lily endosperm?

It is diploid (2n), not the typical triploid (3n) — possibly a link between gymnosperm (haploid) and angiosperm (triploid) endosperm evolution

Six crops that provide ~80% of human kilojoule intake

Corn, rice, wheat, potato, cassava, sweet potato

Grain-to-beef conversion ratio

5–7 kg of grain to produce 1 kg of grain-fed beef

Dominant generation in nonvascular plants

Gametophyte (haploid, n)

Dominant generation in vascular plants

Sporophyte (diploid, 2n)

Transgene

A gene transferred (naturally or via genetic engineering) from one organism to another

CRISPR-Cas9 system

A gene-editing technique using the bacterial protein Cas9 with a guide RNA complementary to a target gene sequence

Asexual reproduction

Generation of offspring from a single parent, without gamete fusion; usually genetically identical to the parent

Sexual reproduction

Reproduction arising from the fusion of two gametes

Clone

A group of genetically identical individual cells

Why is Arabidopsis thaliana used as a model plant?

Its small genome and ease of gene knockout allow scientists to determine individual gene functions and map biochemical pathways

Seed dormancy

A dehydrated (~10% water), metabolically inactive state a mature seed enters until conditions favour seedling survival

Imbibition

The uptake of water by a dehydrated seed, causing it to swell, rupture its coat, and resume embryo growth

Name 3 environmental triggers that can break seed dormancy

Water, fire/smoke chemicals, cold exposure, light, or passage through an animal's digestive system (any 3)

Basal cell (in embryo development)

Forms the suspensor, which anchors the embryo to the parent and provides nutrition

Terminal cell (in embryo development)

Gives rise to most of the plant embryo

Suspensor

A thread of cells anchoring the embryo to the parent plant and providing nutrition

Scutellum

The single cotyledon of a monocot embryo

Radicle

The embryonic root

Hypocotyl

The embryonic axis below the cotyledon (eudicot)

Epicotyl

The point below the first foliage leaves (eudicot)

Coleoptile

The protective covering of a young monocot shoot

Simple fruit

Fruit derived from a single ovary (e.g. nuts)

Aggregate fruit

Fruit formed from many carpels of one flower fusing together (e.g. raspberries)

Multiple fruit

Fruit formed from a cluster of flowers/an inflorescence (e.g. pineapple)

Accessory fruit

Fruit formed from a plant part other than the ovary (e.g. apple)

Fragmentation (plant reproduction)

Asexual reproduction where a stem/root fragment develops into a whole new plant (e.g. potato eyes)

Apomixis

Asexual production of seeds without pollination or fertilisation, from a diploid ovule (e.g. dandelion)

Why are plant breeders interested in apomixis?

It would let hybrid crop plants pass their exact desirable genome intact to offspring

Adventitious stems

New stems arising from a plant's root system that can separate over time to form new individual plants (e.g. King's Holly, Wollemi Pine)

Give one advantage of asexual reproduction in plants

Passes the parent's genetic legacy intact; advantageous in a stable environment; produces stronger progeny than seedlings

Give the biggest advantage of sexual reproduction in plants

Generates genetic variation, enabling adaptation to unstable/changing environments

Self-incompatibility

The biochemical ability of a stigma to reject its own pollen, preventing self-fertilisation

S-genes

Genes responsible for "self" pollen recognition; if a pollen allele matches a stigma allele, the pollen tube fails to germinate or reach the ovary

Totipotency

The ability of a single cell to give rise to all parts of the embryo and adult organism

Callus

A mass of dividing, undifferentiated cells growing at a wound site or in culture

Stock (grafting)

The plant that provides the root system in a graft

Scion (grafting)

The twig grafted onto the stock

In vitro

Work performed outside of a living organism

Artificial selection

Selective breeding by humans for desired traits over generations (e.g. modern corn from wild ancestors)

Hybridisation

The crossing of two true-breeding varieties, transferring genetic material between them (e.g. wheat is a natural hybrid of grasses)

Give an example of natural horizontal gene transfer in plants

The sweet potato's ancestor acquired genetic material from a soil bacterium

Plant biotechnology

Innovations in the use of plants to make products useful to humans, often referring to GM organisms in agriculture/industry

Golden rice

A biofortified GM rice engineered for high vitamin A content, aimed at improving nutrition

How do glyphosate-resistant GM crops work?

Genetic material from glyphosate-resistant bacteria is inserted into crops, allowing farmers to spray herbicide on weeds without killing the crop