BIOL 2202: Angiosperms and Gymnosperms

Characteristics of conifer leaves

-narrow
-needle-like
-have a recessed stomata
-have a hypodermis

lifecycle of a typical gymnosperm

-seed, usually protected by a cone, is shed
-when conditions are right, the seed germinates; roots grow down into the ground and shoots grow up
-seed develops into a small seedling with shallow leaves
-tree continues to grow, and eventually forms cones; male cones release pollen to fertilize female cones
-seeds are produced from this fertilization, and are then dispersed
-the cycle beings again

Male Vs. Female Conifer Cones

Male Cones
-cone axis gives rise to sporophylls and produce pollen
-found at the axil of a bract
-sporangia are on the underside of the microsporophyll
-pollen released in the spring

Female Cones
-cone axis gives rise to woody bracts in their axils
-bud gives rise to sporophylls that fuse to from a scale bearing 2 ovules
-take several seasons to mature
-have an additional bract below each megasporophyll
-sporangia on the upperside of megasporophyll

features of gnetophytes that resemble those of angiosperms

-vessel elements in the xylem
-double fertilization
-a covering on the seeds

Defining Characteristics of phylum Coniferophyta

-includes the world’s largest ad tallest plants
-not prone to permanent disruption of water flow caused by freezing
-70 genera
-630 species
-13 species native to WVDis

Defining Characteristics of Family Arucariaceae

-19 species
-only 1 ovule/scale
-bracts fused to scale or absent
-leaves short, overlapping and prickly
-DNA samples of the 39 remaining wild plants show no discernable variation
-the sole known population is entirely clonal -

Distinguishing features of family Pinaceae

-leaves grow in fascicles (groups of 1-8) after 1-2 years; needles are single until then
-needles are retained for 2-4 years
-leaves better suited to cold and dry
-most sporophylls occur as cones
-some produce seed-bearing structures that resemble berries
-ovulate and pollen cones develop on the same plant but at different locationsDi

Distinguishing features of Family Podocarpaceae

-tropical family
-not of economic importance
-not very ecologically significant
-primarily found in third world countries

Distinguishing features of Family Cephalotaxaceae

-3 genera
-closely related to Taxaceae
-restricted to east Asia with the exception of 2 species of Torreye found in the USA
-small trees or shrubs
-evergreen

Defining features of Family Taxaceae

-3 genera
-7-12 species
-small trees and shrubs
-evergreen with needles spirally arranged and twisted at base
-closely related to Cephalotaxaceae
-seeds partly enclosed by a fleshy red aril
-anti-cancer drug Taxol

Defining characteristics of Family Cupressaceae

-25-30 genera
-130-140 species
-cupressoid species (opposite or whorled leaves)
-2 endemic to New Caledonia and western Tasmania
-1 endemic to Southern Africa
-5 common in various parts of North America : Cupressus, Calocedrus, Chamaecyparis, Juniperus, and Thuja

Characteristics of Cupressus Sp. (Family Cupressaceae)

-16-24 species
-native to warm, temperate regions of the Northern Hemisphere
-evergreen tree or shrub
-adapted to fires

Characteristics of Calocedrus Sp. (Family Cupressaceae)

-3 species
-overlapping scale leaves

Characteristics of Chamaecyparis Sp. (Family Cupressaceae)

-Native to E. Asia and western and eastern North America
-Medium to large evergreen trees
-Foliage in flat sprays
-dimorphic needles
-cones globose to oval

Characteristics of Juniperus Sp. (Family Cupressaceae)

-50-67 species
-widely distributed throughout the northern hemisphere
-juniper berries- mature ovulate cones with fused scales, not true berries
-leaves dimorphic
-juvenile leaves needle-like
-mature leaves overlapping and scale-like

characteristics of Thuja Sp. (Family Cupressaceae)

-5 species
-2 native to North America, 3 to east Asia
-side shoots only in a single plane
-scale leaves arranged in alternating pairs

variations in flower structure

-spiraled or whorled phylotaxy
-radial or bilateral symmetry

lifecycle of a typical angiosperm

-seeds are formed through sexual reproduction. Pollen grains the male gametophyte are produced by the anthers of a flower while female gametophytes in the ovule await fertilization
-pollination occurs when pollen grains are transferred from the anthers of one flower to the stigma of another.
-fertilization occurs when the pollen grain reaches the stigma and germinates to form a pollen tube. In the ovule, sperm cells fertilize egg cells and produce a zygote
-seed development happens when the zygote develops into an embryo within the embryo
-seeds are dispersed by wind, water, or animals
-when a seed lands and is met with the right conditions, it germinates and the process repeats

double fertilization in angiosperms

-2 sperm cells emerge from the pollen tube and reach the ovule
-one sperm fertilizes the egg, forming the zygote
-the other sperm combines with two polar nuclei, forming the endosperm

products of double fertilization and their functions

-zygote whic develops into the embryo
-endosperm which provides nutrients to the developing embryo

sexual vs. asexual reproduction in angiosperms

-asexual reproduction involves cell divisions by mitosis, offspring are genetic ‘clones’ of parents, and in a stable environment a plant that reproduces vegetatively will quickly propagate itself
-sexual reproduction leads to offspring that are genetically different from the parents and each other, result in genetic variation, gametes fuse to form a zygote, is postulated to enhance adaptability to changing environments, and facilitates colonization of new environments

hypothesized evolution of carpels

-evolved from an ovule bearing leaf with ovules arranged along the margins
-the leaf folded around the reproductive structures in response to being exposed to herbivores and the environment
-margins of the leaf eventually met and fused together

hypothesized evolution of stamens

exposed microsporangia that became enclosed while leaf base became narrower giving rise to a filament

carpel vs pistil

-a carpel is a part of the pistil that comprises the style, stigma, and ovary
-a pistil is the female reproductive part of the flower

marginal placentation

ovule(s) attached to the margins of the ovary along the point of suture of the carpel; peas and beans

axile placentation

3 leaves folded around and fused together; ovules attached to the axis like spokes on a bike; immature potato fruit

free central placentation

ovules are attached to one central column; yellow loosestrife mature fruit

parietal placentation

3 leaves folded around eachother and attached to one another; ovules attached to the inner wall of the ovary; mature violet fruit

basal placentation

ovules attached to the base of the ovary; green pepper

position of ovary related to other parts of the flower

-superior ovary (hypogynous) : ovary is attached above the point where other parts of the flower are attached
-superior ovary (perigynous): ovary is attached above the point above the point where other parts of the flower are attached, but it is in the hypanthium
-inferior ovary (epigynous): other parts of the flower are attached above the ovary; small hypanthium present

simple fruit

-derived from a single flower; simple of compound ovary with only one pistil
-tomatoes

aggregate fruit

-develop from separate carpals of a single flower. Each pistil forms a fruitlet (achenes, follicles, drupelets, berries)
-raspberry

multiple fruit

formed from a cluster of flowers (an inflorescence); each flower produces a fruit, but they mature into a single mass
-mulberry

accessory fruit

-fleshy fruit where some or all of the flesh is derived from some adjacent tissue. Ovary, floral parts, and stems are fused together to produce the fruit
-apple (simple, composed of only 1 pistil)
-strawberry (aggregate, develop from 1 flower with numerous pistils)
-pineapple (multiple, derived from the ovaries of single flowers united into a single mass)

fleshy fruit

-the pericarp and accessory parts develop into succulent tissues
-blueberries, lemons, raspberries

dry fruit

-can be dispersed whole or in parts, or they split open to release seeds that are then dispersed by wind, water, or animals
-dandelions, grasses, milkweed

dehiscent fruit

-fruits that split open at the time of maturity
-poppy, legume

indehiscent fruit

-dry fruits that open up only upon deterioration or spread by consumption by animals
-sunflowers, dandelions

pollen vectors that effect pollination in angiosperms

-insects
-vertebrates
-wind
-water

pollination syndromes for beetles

-flowers dull or ream red colored with a strong, sweet odor
-“mess and soil” pollinators
-Magnolids and aroids

pollination syndrome for flies

-flowers look like rotting flesh or fecal matter
-foul odors and look like decaying matter
-no nectar reward
-some elaborate flower morphology to hold flies in a trap while flowers proceed through development
-”mess and soil” pollination
-amorphophallus titanum

pollination syndromes for wind

—have a reduced perianth
-imperfect flowers (monoecy or dioecy)
-exerted stamens
-light, dry, thin-walled pollen
-enlarged stigmatic surface
-do not have a scent or nectar

pollination syndromes for bees

-flowers are often yellow, blue, or purple with UV nectar guides
-often bilateral; landing platforms
-nectaries are present
-produce small amounts of pollen
-fragrant
-have a specific placement of pollen
-asteraceae and saxifragaceae

pollination syndromes for butterflies

-flowers blue, pink, yellow, or orange
-have a narrow floral tube; horizontally or vertically oriented
-dinural nectar production
-dinurally receptive stigma
-pleasant odor
-”mess and soil” pollen placement or very specific pollen placement
-milkweeds

pollination syndromes for moths

-flowers cream colored
-nocturnal nectar production
-nocturnally receptive stigma
-sometimes very long and horizontally oriented floral tube
-with a strong sweet odor
-”mess and soil” pollen placement or very specific
-Virgin’s Bower

pollination syndrome for hovering bird pollination

-flowers are bright red, orange, or yellow
-have long narrow horizontally oriented floral tube
-sticky pollen
-lots of sugar-rich nectar
-no odor
-”mess and soil” or specific pollen placement
-diurnal
-christmas cactus, cardinal flower

pollination syndromes for bats

-flowers are dull red or cream colored
-have sturdy, often bell shaped flower parts
-lots of pollen or nectar
-a strong sweet, musky odor
-nocturnal blooming
-echo-locatable positioning of flowers on stem or pendant inforescences
-“mess and soil” pollen placement either on the head or entire front of the body
-Parkia

pollination syndrome for non-flying mammal pollination

-flowers are dull colored, large and sturdy, or grouped together as multi-flowered inflorescences
flowers lay on the ground
nocturnal blooming
-strong, pungent odor
-lots of sugar-rich nectar
-lots of pollen
-“mess and soil” pollen placement
-banksia and protea

pollination syndrome for perching bird pollination

-bright colors
-sturdy perch for bird to land on
-lots of pollen and nectar
-”mess and soil” pollen placement
-diurnal
-banana