Biology 10: Topic 6d: Vascular Plants: Flowering

Angiosperms
- seeds enclosed in fruit
- often referred to as flowering plants

Evolutionary adaptations that allowed angiosperms to spread:
1. Herbaceous stems
2. More efficient vascular system with xylem vessels (vízszállító cső)
3. Complex reproduction: pollen dispersed by insects (and other animals) reduces randomness, coevolution of pollinators and flowers, ovule (which develops into the seed) is enclosed in the ovary (zárt magház), which develops into the fruit, increasing protection and dispersal

Flower structure:

Image from: www.waynesword.palomar.edu

- the anther (portok) and filament (porzószál) together form the stamen (porzó)

- the stigma (bibe), the style (bibeszál) and the ovary (magház) form the pistil (termő)

- in monocots there is no differentiation of the petals (sziromlevelek) and sepals (cseszelevelek), instead they have tepals (lepellevelek)

- flowers can be catagorized in various ways:

complete flower: has pistil, stamen, petals and sepals (in other words, all the parts)

incomplete flower: lacks one or more parts, for example the oak flowers have no petals

bisexual flower (kétívarú) has both male and female parts
unisexual flower (egyívarú) has only male OR female parts (sometimes both male and female flowers are found on the same plant) eg. squash flowers

- the whole plant can be catagorized as monoecious (egylaki) - plant has both male and female parts - or diecious (kétlaki) - the whole plant is either male or female.

Reproduction in Angiosperms

Image from: www.commons.wikimedia.org

-in the ovary, there can be more than one ovule that forms.

-pollination can occur by wind or with animals (particularly insects) carrying the pollen between flowers.

- some plants can self-pollinate, while others must cross-pollinate

- fertilization in angiosperms is double fertilization where 1 sperm fertilizes the egg (one of the synergids) to form the zygote (2n) and the other sperm fertilizes the central cell (called polar nuclei in this figure) to form the endosperm (3n)

- visible signs of fertilization include petals falling off the flower and the swelling of the ovary into a fruit.

Fruits can be catagorized (biologically):

True - formed from only the ovary

Accessory - formed from the ovary and other flower parts
Fruits are commonly classified as:
1. Simple fruits: Fruits that develop from a single pistil (the ovary may contain multiple ovules), they can be either fleshy or dry
2. Aggregate fruits: Fruits formed by more than one pistil in the same flower.
3. Multiple fruits: Fruits formed by multiple pistils from multiple flowers (eg. mulberry - eperfa gyümölcse)

Fleshy - as the name suggests, the fruit contains considerable water content, its wall becomes soft as it matures, eg berries, apples, etc. They can be classified as drupes, berries or pomes
Drupe: it has only 1 seed surrounded by a hard, stony wall, a fleshy middle section and a very thin skin, eg. plums, peaches, coconuts, etc

Examples of drupes

Berry: a fruit in which the ovary wall usually becomes enlarged and juicy. Contains multiple seeds. Eg. blueberries, grapes, tomatoes There are 2 specialized kinds of berries: pepo - berries with a relatively hard outer layer (rind) (eg. squash, cucumber, watermelon) and herperidium - berries with a leathery rind, inner portion divided into segments (eg. oranges, lemons)

Examples of berries

Pome: (comes from the French word for apple - pomme) formed by a group of pistils, surrounded by and united to the sepals or receptacle. It contains 5 or more ovules. (eg. apples, pears)

Dry - contains little water, eg. beans, nuts, samara, cypsela (dandelion fluff)

can be grouped as dehiscent, which means that they open to release the seeds at maturity, or indehiscent, which don't open (and usually only contain 1 seed)
Dehiscent fruits include:
-legumes (peas, beans) - pod splits on both sides at maturity

-follicles (columbine) - pod splids on only one side at maturity

-capsules (poppies, lilies) - top of the capsule opens to release seeds or it splits open along the septa

Indehiscent fruits include:
- achenes (sunflower) - one seed attached to fruit wall at a single point

- nuts (beech, oak, etc) - one seed surrounded by a greatly thickened, hardened wall

beechnut

Acorns

- samara (maple) - one or two seeds, where part of the fruit wall forms one wing

- grain (wheat, corn) - one seed with the seed coat fused to it

Corn

Wheat

Germination of the seed:

-occurs after a period of dormancy (can last days to 1000s of years)
- it is the growth of the plant within the seed and sprouting (csírázás) out of the seed
- it depends on internal conditions (eg. hormones) and external conditions (eg. temperature, water, oxygen and sometimes light or dark)

Classification of angiosperms:

1. Dicots (kétszíkűek)

-developed first

Characteristics:

a. taproot

b. herbaceous or woody stem

c. branched veins in leaves

d. flower with petals and sepals

e. 2 cotyledons, endosperm enveloped in them

f. floral parts in 4s or 5s or multiples of 4 or 5

There are over 250 families of dicots, some examples include:

- Buttercup family (boglárkafélék): buttercups, marigolds, anemones