Vascular Tissue & Plant Evolution

This course is focused on seed plants, so that is where we will spend most of our time. However, to fully understand plant reproduction and taxonomy we have to spend a little time investigating the non-seed plants as well. Therefore we will look at the phylogenetics and reproduction in non vascular plants (all non seed plants) first to gain the concept of "alternation of generations". We will then move on to discussing vascular tissue (most seed plants, some non seed plants), and then move on to reproduction in the seed plants only. Alternation of generations is still present in the seed plants but instead of the gametophytes being dominant like in the non vascular plants the sporophytes are dominant in the seed plants. We will also be introduced to the idea of flowers and fruits.

Central Questions and Topics

Generally understand the alternation of generations in bryophytes (non vascular and non seed plants).
Tell the story of the evolutionary history of vascular tissue in plants.
How does transpiration, capillary action, and root pressure explain why tree species each have a "height limit" above which they cannot grow taller? How are xylem and phloem involved? Why is it important for NO air bubbles to be present in the vascular tissue?
Scale Trees (Lycopods), coal, and the carboniferous rainforest collapse - what's going on?

Bryophyte Phylogeny - Non Vascular Plants

Tracheophyte Phylogeny - Vascular Plants

Angiosperm Phylogeny - Flowering Plants

Monocot vs. Eudicot - here are the distinguishing characteristics between these two large groups of plants

The current state of flowering plant systematics - APG IV - this describes how angiosperm plants are currently classified...this is changing

Simplified Phylogeny of Plants

Nonvascular Plant Reproduction - Alternation of Generations

do not have roots, stems, leaves - or specialized conductive tissues
must directly absorb nutrients and water and move it around via osmosis
without woody tissue there is a limit on growth
need water for reproduction
mosses, liverworts, hornworts
complex reproductive live cycle - alternation of generations
- - gametophyte - sexual reproduction, produces gametes (egg and sperm - haploid cells that each carry one set of chromosomes - need water for sperm and egg to meet - once egg and sperm fuse - gives rise to diploid zygote sporophyte
    - - each plant is either male or female
        male - sperm - antheridium
        female - egg - archegonium
  - sporophyte - asexual, diploid, sporangium (produces haploid spores), relies on gametophyte for water and nutrients - spores release and germinate - send out protonema - produces gametophytes

Tissues and their Functions - emphasis on vascular tissue

conductive tissues can move nutrients and water around the plant - thus giving them an advantage
ferns & horsetails, angiosperms, gymnosperms
primary growth (herbaceous) vs secondary growth (woody)
dermal tissues
- - outer layers, prevent damage and water loss
  - epidermis (can have waxy cuticle or trichomes)
  - root hairs - maximize root surface area for absorption
vascular tissues
- - move nutrients and water around the plant
  - xylem - water transport
    - - evapotranspiration - how do large trees get water from the ground to the top? Why would the plant want to release valuable water?
      - collenchyma - herbaceous support
      - sclerenchyma (stiff lignin walls) - woody plant support
  - phloem - carries sugar from leaves to other parts of the plant
    - - sieve cells get loaded with sugar and take on water from xylem to make a syrup to move around the plant where needed
ground tissues (parenchyma cells)
- - photosynthesis, storage of food - does many tasks!
  - mesophyll - destination of water in xylem - pockets in the leaf that fill with water
  - stomata bring in carbon (release oxygen) from (to) the atmosphere
    - - when leaf is dry, guard cells sag and close
Types of plant organs (each contains all 3 types of tissue)
- - root - absorbs water and nutrients, leftover food, anchor
  - stem - transport fluids, stores food, holds up leaf, meristems that create new growth
  - leaf - exchange gases with atmosphere, collects solar radiation to conduct photosynthesis