Topic 7 - Plant Form, Physiology, and Diversity

Which eukaryotic supergroup do land plants descend from?

Archaeplastida

What are the origins of land plants from aquatic algae?

1. Plastid Origin

2. Unicellular green algae

3. Streptophyte algae

4. Mosses/Liverworts/Hornworts

5. Vascular Plants

6. Seed Plants

What adaptations that are unique to plants?

• Alternation Between Haploid + Diploid generations

• Presence of Apical Meristem

• Presence of Lipid/Waxy Cuticle

• Presence/Absence of a Vascular System

• Differentiated Body Sections

• Presence/Absence of Seed Formation

• Prescence/Absence of Flowers

How do plants alternate between haploid + diploid generations?

Via a haplodiplontic life cycle (alternation of generations) that toggles between two phases: gametophyte(1n) and sporophyte (2n):

• Sporophyte produces 1n spores via meiosis that grows into gametophytes

• Gametophytes produce gametes(sperm/egg) via mitosis which fertilize to form a diploid zygote (sporophyte)

What are haploid plant generation/stage?

Gametophyte

What are diploid plant generation/stage?

Sporophyte

Gametangia

specialized structs. that give rise to gametes

Antheridium

male gamatangium

Archegonia

female gametangium

What are the stages of embryonic plant growth

1. Embryo is protected by the female gametophyte (haploid stage) as it grows

2. Embryo grows into Sporophyte (diploid stage)

3. Sporangia will release haploid spores

What stage do “simple” land plants predominantly reside?

gametophyte

What stage do “complex” land plants predominantly reside?

sporophyte stage

What is the difference between fern gametophyte stage and the fern sporophyte stage?

• Fern sporophyte is large, dominant (2n) plant that appears as the familiar fern plant

• Fern gametophyte is a delicate, haploid (1n) that appears as a prothallus (thin heart shaped plant), lacking vascular tissue

Apical Meristem

region of cells capable of division in the root and shoot tips of plants (can be located at the top or bottom of [plant)

Why is the presence of Apical Meristem an important plant adaptation?

it allows for “indeterminate growth” aka a plants ability to grow continuously through a plant’s life as apical meristem contains actively dividing stem cells at root and shoot tips

Why is the presence of a lipid/waxy cuticle an important plant adaptation?

its hydrophobic barrier minimizes water loss via transpiration (evaporation of water from stomata) which allows for plants to survive in dry, terrestrial environments

Why is the presence/absence of a vascular system an important plant adaptation?

• allows for increased plant height as vascular tissue allows for rigidity necessary for vertical growth

• aids water/nutrient transport over long distances via xylem

• aids survival in dry environments

Why is differentiated body sections an important plant adaptation?

it enables specialization for survival on land via optimizing water absorption, structural support, and photosynthesis

• Vascular plants possess leaf, stem, and root

• Non-vascular plants lack leaves, stems, and roots

Why is the presence/absence of seed formation an important plant adaptation?

• it allows for plants to break dependence on water for reproduction and colonize dry lands

• seeds protect the embryo from environmental hazards, provide nutrients, allow for dormancy until optimal growth conditions, enable wide dispersal

  • Vascular seedless plants reproduce via spores

  • Vascular seed plants reproduce via seeds

Why is the presence/absence of flowers an important plant adaptation?

• it helps angiosperms (flowering plants) to maximize reproductive success via pollinator attraction which allows for cross-pollination, genetic diversity, and wide seed dispersal

• its absence helps gymnosperms/ferns where wind pollination is more reliable (forming flowers = energy loss → isn’t necessary in windy environments)

How are plants classified?

• Non-Vascular Plants (Bryophytes)

• Vascular Plants (Tracheophytes)

What are bryophytes?

Non-vascular plants that absorb water on all their exposed surfaces (the gametophyte is the dominant stage of their life cycle)

Examples: liverwort, moss, hornwort

Explain the vascular system in tracheophytes.

Tracheophytes possess tissues specialized in material transport from one plant to another which consists of the xylem and phloem

What are tracheophytes?

Vascular plants that posses highly conserved organization enabling survival on land because of their roots, stem, and leaves

What are the role of roots in the vascular system?

transfer water and minerals from soil to the rest of the plant via a prominent vascular tissue system

What are the role of leaves in the vascular system?

acts as large photosynthetic organs

What is the xylem?

a component of the vascular system that transports water (in ONE direction) and minerals via vessel elements and tracheids which are dead @ maturity (have primary + secondary wall)

What is the phloem?

a component of the vascular system that transports sugars (move bidirectionally) and proteins (sap)

**In angiosperms, sieve-tube elements surrounded by various support cells contain the sugar solution**

How are bryophytes classified?

• Moss

• Liverworts

How are tracheophytes classified?

• Seedless Plants

  • Fern

  • Club Moss

• Non-Seedless Plants

  • Gymnosperms

  • Angiosperms

What are seedless vascular plants?

Includes club mosses, whisk ferns/ferns, and horsetails by which MOST of these species have Sporophyte stage as its dominant stage that consists of fronds (large compound leaves)

What are the two major innovations that allowed seed plants to reproduce in the absence of water?

Seed and Pollen

What role do seeds play in the embryonic process of plants?

Seeds act as a protective entity allowing for embryos to lie dormant until conditions are right for germination

What are spermatophytes?

A group of seed-producing vascular plants in which which the gametophyte (gamete-producing) generation is reduced even further

What are gymnosperms?

Non-seedless plants in which the gametophyte generation takes place inside the cone

How does pollination and fertilization occur in gymnosperms?

Exposed female cones (gametes) are fertilized by pollen (male gametophyte) from male cones that are blown by the wind. The pollen tube forms, allowing pollen to migrate towards the female gametophyte which forms a zygote (2n) as seeds which are dispersed by the wind to grow into mature trees.

What are angiosperms?

Non-seedless, flowering plants that bear seeds in fruit which protect the gametes and the embryo during development

What are the components of angiosperms’ flower?

stamen, carpels, petals, and sepals

What is the stamen?

produce the male gametophyte where pollen is stored

What are the carpels?

produce the female gametophyte and the embryonic sac (found within ovule)

What is a reproductive event unique to angiosperms?

Double fertilization which involves two SEPERATE fertilization events occurring in the embryonic sac

What occurs upon fertilization of angiosperms?

the ovary of the flower develops into fruit (as the fruit natures the seeds also mature)

What are cotyledons?

leaves in an embryonic seed

What are the two main groups that flowering plants are classified as?

Monocots and Eudicots via the # of cotyledons in the seedlings

What are the 3 basic types of cells present in MOST plants?

Parenchymal, Collenchymal, and Sclerenchymal

What are Parenchymal plant cells?

Structure: cube-shaped, loosely packed, thin-walled, contain chloroplasts

Function: photosynthesis storage

What are Collenchymal plant cells?

Structure: elongated, irregularly thickened walls

Function: support + wind resistance

What are Sclerenchymal plant cells?

Structure: VERY thick cell walls containing polymers

Function: support + strength

What are the 2 categories of plant tissue systems?

• Meristematic tissue

• Permanent (Non-meristematic) tissue

What are the 3 types of meristematic tissues?

• apical meristems → located @ tip of stems + roots

• lateral meristems → facilitates growth in thickness

• intercalary meristems → occurs only in monocots

What are the 3 types of non-meristematic (permanent) tissues?

• dermal tissue → covers + protects the plant

• vascular tissue → transports H2O, minerals, and sugars to diff. plant parts

• ground tissue → site 4 photosynthesis (supporting matrix for vasc. tissue) + helps store water + sugars