Lecture 2
What distinguishes a seed plant?
-Axillary lateral branching + produces seeds (ovule + pollen)
-Gymnosperm + Angiosperm
What defines a Gymnosperm from an Angiosperm?
-Naked seeds: pollen cone & seed cone produce seeds
-No floral structure
-No double fertilization
Explain stamen evolution, 2 types of dehiscence & 2 types of attachments in eudicots
-The modified leaf on which sporangia are attached reduced into more specialized structure (anther & filament)
Dehiscence
1. Longitudinal: explosive all at once
2. Poricidal (sac-like): wind/animal shake over time
Attachment:
1. Basifixed: stiff >pollinator lands on
2. Versatile: flexible > pollinator & wind movement
What species change our understanding of the evolution of monocots and eudicots? How did it change our understanding?
Amborella tricopoda:
Earliest flowering group to evolve in angiosperms
Monotypic (1 member in its family)
Endemic shrub from New Caledonia
Discovered & published in 2004
Dioecious, staminodes in female flower
insect pollination, pollen is reward
Dicot (eudicots & basal angio) used to be considered as monophyletic group, but Amborella split them into 2 different monophyletic > reorganizing phylogenetic trees
What is a fruit and what plant organ does it evolve
from?
A fruit = a ripened pistil that bears seeds (+ accessory parts sometime) An ovary develops into a fruit
What defines angiosperms?
-Enclosed seeds (ovules) within ovary
-Highly reduced male gametophyte (pollen grain with only 3 cells)
-Penetrative pollen tube growth
-Double fertilization: Each sperm fertilizes the egg cell & the polar nuclei -> fertilized egg (2N) & endosperm (3N)
What are the 6 groups of Angiosperms?
Amborella
Nymphaeales
Austrobaileyales
Magnoliids: 3rd largest
Monocot: 2nd Largest
Eudicot: Largest
Describe different ways to tell the difference between monocots and eudicots
*Synapomorphies
Monocots
Monocots = more advanced than basal dicots (2 cotyledons)
Adventitious root system (fibrous roots)
Parallel leaf venation
Herbaceous (lost secondary growth, i.e. wood formation)
Eudicots:
2 cotyledons
Taproot
Reticulate (netty) venation
Secondary growth
Explain the terms carpel, pistil, ovary, ovule and gynoecium. How are they related to each other and how are they different?
Carpel = pistil = megasporophyll, composed with stigma (pollen reception), style (btw stigma & ovary, pollen tube grows), and ovary.
Ovary = a chamber where ovules are borne, turns into fruit
Ovule = turns into a seed
Gynoecium = all pistils together
What are three ways to classify fruit with examples?
1. Simple vs compound ovary
e.g. pea pods vs tomatoes
2. Dry vs fleshy
e.g. sunflower seeds vs pumpkins
3. Dehiscent (open) vs indehiscent (closed)
What defines a flower and why are flowers considered short, determinate shoots?
-Short shoot with specialized appendages (modified leaves) for reproduction
> Fertile appendages = stamens + pistil(s)
>Sterile appendages = sepals (calyx) + petals (corolla)
-Axis compressed & determinate = when buds turn into flowers, no further growth occurs
What are some features of beetle pollination?
Pollination of basal angiosperms
-Nymphaeales: chamber flower pollination (flower open/close); thermogenesis (traps heat)
-Austrobaileyales: flies, including midges (star anise); female gall midges lay eggs in flower & eat pollen (Schisandra henryi)
-Magnoliids: chamber flower pollination; brush pollination (pollen as reward)
Name and describe the basal angiosperm groups.
Amborella:
-Most ancient group
Nymphaeales:
syncarpous
aquatic herbaceous
tepals & bracts are integrated
tepaloid (modified tepals) stamen
Beetle pollination (chamber flower pollination)
Austrobailyales:
Insect pollination (leaf litter and water breeding flies, including midges)
Magnoliids:
3rd largest group
trimerous flowers (multiples of 3)
pollen with 1 pore
mostly branching veined leaves
chamber flower pollination (Magnolia), brush pollination & wind pollination (Piper)
Can there be more than one compound pistil in a flower?
No!
Simple pistil = 1 carpel, a flower can have many simple pistils
Compound pistil = multiple carpels fused, a flower can have only 1 compound pistil.
What is Placentation? Name and describe the types of placentation.
The swellings of the plant tissue that connects the ovules are borne
Marginal = placenta along the margins of the carpel, with 1 locule (simple pistils)
Axile = the placenta in the central axis, 1 locule per carpel (compound pistil)
Parietal = multiple placentas to the inner ovary wall within the fused carpels of the compound pistil. Only 1 locule.
What is the typical order of the floral whorls?
1. Sepal
2. Petal
3. Stamen
4. Carpel
Understand the ideas of Chamber Flower and Brush pollination.
Chamber flower pollination (magnolia)
Beetles are attracted to pollen
Tepals close at night -> beetles get pollen inside the flower, tepals re-open in the morning -> beetles carry pollen to another flower
Brush pollination (piper)
-insects eat & transfer pollen to other flowers
What is a staminode? What two flower whorls could they develop from?
sterile stamens (do not produce pollen, no anthers)
Small & vestigial OR large & petal-like
Petals may have originated as staminodes
Extra petals = modified stamens in many double flowers
What is syncarpy and what are some of the advantages of this evolutionary trait?
Syncarpy = fused carpel = compound ovary
-greater flexibility for seed dispersal with lower cost (follicle, capsule fruit types)
-pollen has more fertilizing potential than an apocarpous flower (simple pistil)
-greater pollen competition
-greater seed set & protection (achene, capsule)
Know the different types of ovary position and which
type is more primitive and advanced with examples.
(Draw each ovary position!)
1. Superior ovary = hypogynous PRIMITIVE
2. Superior ovary with hypanthium = perigynous DERIVED
3. Inferior ovary = epigynous MOST DERIVED
4. Inferior ovary with hypanthium = epigynous MOST DERIVED
*Some plants have ovary sunken into stem tissue (e.g. cacti)
What are the 4 main groups of Gymnosperms & what distinguishes each group of Gymnosperms?
1. Ginkgo: 1 family, 1 genus, 1 species (Gingko biloba); dioecious TREE (staminate OR ovulate); Bilobed leaves with dichotomous venation
2. Cycads: 3 families, 1 genus (Cycas) & 105 species; Tree or shrub; Usually dioecious;
3. Gnetales (3 families):
i. Welwitschiaceae: 3 genera, dioecious, opposite leaves joined at the base (looking like a spider)
ii. Gnetaceae: 1 genus, 30 species; dioecious; tree & vines
iii. Ephedraceae: 1 genus, 65 species; Native to southwestern North America; reduced leaves & photosynthetic stems
4. Conifer: 68 genera & 545 species; Trees & shrubs; Can be deciduous (shed needles); Dioecious & monoecious (seed cone & pollen cone on same plant) species
Describe different ways to tell the difference between monocots and eudicots.
Monotots:
Only 1 cotyledon, more advanced than basal dicots (2 cotyledons)
Adventitious root system (fibrous roots)
Parallel leaf venation
Herbaceous (lost secondary growth, i.e. wood formation)
Eudicots:
2 cotyledons
Taproot
Reticulate (netty) venation
Secondary growth
Did basal angiosperms give rise to monocots?
No! Evolution is not linear. Monocots lost secondary growth.
Draw and describe the series of evolutionary steps of one of many ways a seed-bearing leaf may have become a carpel via folding. What are the 2 ways of an enclosed structure of a seed-bearing leaf?
Seed-bearing leaf (megasporophyll) with ovules exposed on the rim of the leaf, curled inside, and fused on the edge to give more protection.
1. Ascidiate (sac-like): primitive, stigmatic surface at the mouth (avocado)
2. Plicate (folded): more advanced (pea pods)
Explain different types of fruit
Know the five evolutionary trends in perianth
evolution. EXAM Q
Fruit types:
1. Aggregated fruits: several ripened pistils in a single flower (blackberries/raspberries)
2. Multiple fruits: MOST ADVANCED several flowers/whole inflorescence including ovaries from many flowers/bracts/inflorescence stems all fused into single fruit (pineapples/figs/mulberries)
3. Accessory fruits
5 evolutionary trends of synorganization:
1. Differentiation of floral parts (undifferentiated tepals -> calyx & corolla)
2. Reduction in # or loss of floral parts to save energy
3. Changes in symmetry from radial -> bilateral -> asymmetrical
4. Compression of the receptacle & change from spiral -> whorled arrangement of flower
5. Fusion of floral parts (free->fused)