Bot-Lec (Sem-1) - Chapter 15: Flowers and Plant Reproduction

flowers

the reproductive organs of angiosperms

pollen grain

a two-celled, immature male gametophyte; protects the sperm cells during pollination; withstands decomposition; one cell will give rise to sperm cells; the other develops into a pollen tube

pollen tube

transports the sperm to the ovary

ovule

stalked structure that develops on the ovary wall of a carpel

megaspores

four haploid cells in the ovule that form after meiosis; contains an embryo sac (female gametophyte), nucellus (surrounding tissue), and integuments (one or two protective layers

female gametophyte

embryo sac within a megaspore

nucellus

surrounding tissue within a megaspore

integuments

one or two protective layers of a megaspore

pollination

the transfer of pollen grains to a stigma by wind or animals

coevolution

joint evolution of two or more species interacting in close ecological fashion; underwent by flowering plants and their pollinators

insects; insect wings; greater seed yield

suggested reasons behind the wide distribution and diversity of plants despite their immobility

cone scales

ovules were naked and vulnerable

flowering plants

ovules are enclosed in closed carpels for protection against herbivores

birds

pollinate flowers with red and/or yellow petals and form tubes for nectars; some species have beaks as long as the floral tube; poor sense of smell so flowers they pollinate don’t have fragrance

beetles/honeybees

can’t detect red wavelengths and drowns in nectars inside flowers with tubes; pollinate flowers with strong, sweet odors and bright yellow, blue, purple components

butterflies

day foragers and attracted to sweet-smelling, red and upright flowers with a horizontal-like landing platform; have long, narrow mouthparts that fit narrow floral tubes

moths

night foragers and pollinate flowers with strong, sweet odors and white or pale-colored petals, which are more visible in the dark; long narrow mouthparts that fit narrow floral tubes

Madagascar hawkmoth

has a 22 cm-long mouthpart similar in length to an orchid floral tube

hawkmoths

hover around floral tubes not needing a landing platform

inflorescences

groups of flowers, as opposed to flowers that occur singly

(indeterminate) racemose; (determinate) cymose

two types of inflorescence

racemose

indeterminate; terminal bud continues to produce new flowers

raceme; spike; catkin; spadix; corymb; umbel; head/capitulum

seven types of racemose inflorescence

raceme

a type of racemose; an elongated axis-bearing stalked flowers; e.g. mustard (Brassica juncea)

Brassica juncea

mustard; an example of raceme inflorescence

spike

a type of racemose; same as raceme, but flowers have no stalks (pedicels); e.g. Achyranthes

Achyranthes

chaff flower; an example of spike inflorescence

catkin

a type of racemose; spike with unisexual flowers; e.g. Morus

Morus

mulberry; an example of catkin inflorescence

spadix

a type of racemose; spike with fleshy axis enclosed by one or more large bracts; e.g. Colocasia, Musa, etc.

Colocasia

taro; an example of spadix inflorescence

Musa

banana; an example of spadix inflorescence

corymb

a type of racemose; the axis is short, and the lower flowers have longer stalks than the upper ones, thus all flowers come to the same level; e.g. candytuft (Iberis)

Iberis

candytuft; an example of corymb inflorescence

umbel

a type of racemose; the axis is short and bears a cluster of flowers with stalks of equal length arising from a common point; e.g. coriander (Coriandrum sativum)

Coriandrum sativum

coriander; an example of umbel inflorescence

head/capitulum

a type of racemose; the main axis is a flattened, more or less convex structure on which sessile flowers (florets) are arranged in a centripetal order; the inflorescence is surrounded by prominent bracts; e.g. sunflower (Helianthus annuus), marigold (Tagetes), etc.

Helianthus annuus

sunflower; an example of head/capitulum inflorescence

Tagetes

marigold; an example of head/capitulum inflorescence

cymose

determinate; terminal bud stops growing and lateral flowers are produced from axillary buds

monochasial cyme; dichasial cyme; polychasial cyme

types of cymose inflorescence

monochasial cyme

a type of cymose; the main axis terminates in a flower and one lateral branch axis develops from its base which also ends in a flower; e.g. Begonia, cotton (Gossypium)

Begonia

begonias; an example of monochasial cyme inflorescence

Gossypium

cotton; an example of monochasial cyme inflorescence

dichasial cyme

a type of cymose; two lateral branches develop on either side of the terminal flower of the main axis; the lateral branches also end in a flower and may again branch similarly; e.g. jasmine (Jasminum), Dianthus, etc.

Jasminum

jasmine; an example of dichasial cyme inflorescence

Dianthus

carnation; an example of dichasial cyme inflorescence

polychasial cyme

a type of cymose; more than two lateral branches arise form the base of the terminal flower; e.g. Calotropis

Calotropis

milkweed; an example of polychasial cyme inflorescence

hypanthodium; cyathium; verticillastor

special types of inflorescence

hypanthodium

a special type of inflorescence; the main axis for cup-shaped receptacle with a small opening at the top; flowers are enclosed within the cup in cymose groups; e.g. Ficus

Ficus

figs; an example of hypanthodium inflorescence

cyathium

a special type of inflorescence; here the involucre forms a cup; a single flower without a perianth arises in the middle surrounded by a large number of male flowers represented by stalked stamens; e.g. Euphorbia

Euphorbia

spurges; an example of cyathium inflorescence

verticillastor

a special type of inflorescence; in this type of inflorescence, typical of plants with opposite leaves, a cyme arises in each leaf axil; the first axis ends in a flower; two branches arise below it bearing branches in an alternating manner; flowers are sessile and appear as a cluster around the node; e.g. Ocimum

Ocimum

basil; an example of verticillastor inflorescence

seed

the enlarged and mature ovule with its enclosed embryo and consists usually of supply of stored food; typically dry, dormant, and very resistant to environmental stress

fertilization

fusion of a sperm nucleus and an egg nucleus

double fertilization

occurs in flowering plants; one sperm nucleus fuses with that of the egg, forming a zygote; the other sperm nucleus and the endosperm mother cell fuse together; results in a zygote (2n) and an endosperm (3n); endosperm forms only in flowering plants nourishing the embryo

cotyledons

seed leaves; develop as part of the embryo

seed coat

matured/thickened integuments

fruit

a developed and ripened ovary or ovaries, sometimes with other floral organs and other plant parts; seed protection and dispersal

simple; aggregate; multiple

three types of fruits

simple fruit

a type of fruit that forms from a single pistil

dry indehiscent; dry dehiscent; fleshy

three types of simple fruits

dry indehiscent

a type of simple fruit; at maturity; the dry fruit does not split open

achene; grain; nut

types of dry indehiscent fruits

achene

a type of dry indehiscent fruit; close-fitting pericarp surrounding a single seed; e.g. sunflower (Helianthus annuus)

grain

a type of dry indehiscent fruit; close-fitting pericarp fused to a single seed; e.g. corn (Zea mays), wheat (Triticum aestivum)

Zea mays

corn; an example of grain

Triticum aestivum

wheat; an example of grain

nut

a type of dry indehiscent fruit; thick, woody pericarp surrounding a single seed; e.g. walnut (Juglans), hazelnut (Corylus)

Juglans

walnut; an example of nut

Corylus

hazelnut; an example of nut

dry dehiscent

a type of simple fruit; at maturity, dry and splits open

legume; capsule; schizocarp

three types of dry dehiscent fruits

legume

a type of dry dehiscent fruit; pod that splits along two sides; e.g. beans (Phaseolus), peas (Pisum)

Phaseolus

beans; an example of legume

Pisum

peas; an example of legume

capsule

a type of dry dehiscent fruit; fruit opening by several splits of pores; e.g. cotton, poppy

Papaver

poppy; an example of capsule

schizocarp

a type of dry dehiscent fruit; fruit splitting into one-seeded segments; e.g. dill (Anethum graveolens)

Anethum graveolens

dill; an example of schizocarp

fleshy fruits

a type of simple fruit; do not usually split open; palatable and adapted for surviving the digestive enzymes in the animal gut

drupe; berry

two types of fleshy fruits

drupe

a type of fleshy fruit; one to two seeded; the innermost pericarp layer, stony and enclosing the seed(s); e.g. plum (Prunus), peach (Prunus persica)

Prunus

plums; an example of drupe

Prunus persica

peach; an example of drupe

berry

a type of fleshy fruit; one to many seeded; no stony innermost layer of pericarp; e.g. tomato (Lycopersicon esculentum), grape (Vitis vinifera)

Lycopersicon esculentum

tomato; an example of berry

Vitis vinifera

grapes; an example of berry

hespiridium

a special type of berry; all citrus fruits

aggregate fruits

a type of fruit that is formed by the fusion of several pistils of one flower; e.g. raspberry (Rubus idaeus), cherimoya (Annona cherimola)

Rubus idaeus

raspberry; an example aggregate fruit

Annona cherimola

cherimoya; an example aggregate fruit

multiple fruits

a type of fruit formed by the fusion of several separate pistils of several grouped flowers; e.g. pineapple (Ananas comosus), fig (Ficus)

Ananas comosus

pineapple; an example of multiple fruit

seed dispersal

the scattering of seeds; for the purpose of growing without too much competition from each other

modified stems; parthogenesis; vegetative propagation; tissue culture propagation

asexual reproductive modes of flowering plants

runner; rhizome; corm; tuber; bulb

five types of modified stems