Bot-Lab (Sem-1) - Chapter 15: Flowers and Types of Inflorescence

flowers

the reproductive organs of angiosperms; produce the necessary cells (egg and sperm) to produce a zygote; determinate stem with crowded appendages, and with internodes much shortened or obliterated

produce offspring genetically identical to parents; produce offspring genetically different to parents

two major functions of plant reproduction

fruit

a developed and ripened ovary/ovaries, sometimes with other floral organs and other plant parts

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

complete

flowers that have all four parts: sepals, petals, stamens and pistils

incomplete

flowers that lack one or more of four parts: sepals, petals, stamens and pistils

perfect

bisexual flowers; flowers with both male and female reproductive parts (pistil and stamen)

imperfect

unisexual flowers: flowers with only one male or female reproductive part (pistil or stamen)

monoecious

having both female and male flowers in one plant

dioecious

having separate plants for male and female flowers

regular symmetry

actinomorphic flower; parts (whorls) of a regular flower, i.e., the calyx, corolla, androecium, and gynoecium, are arranged symmetrically around the floral axis

irregular symmetry

the petals and sepals are not uniform in shape and they are arranged around the floral axis in an irregular fashion, i.e., asymmetrically

polypetalous

having separate petals

polysepalous

having separate sepals

polytepalous

having separate tepals

gamopetalous

having fused petals

gamosepalous

having fused sepals

gamotepalous

having fused tepals

superior

an ovary attached above other floral parts

inferior

an ovary which lies below the attachment of other floral parts

epigynous

inferior ovary; having the ovary enclosed in the receptacle, with the stamens and other floral parts situated above

perigynous

sub-inferior ovary; ovary is surrounded by the fused bases of flower parts (calyx, corolla, androecium) that surround the ovary

hypogynous

superior ovary; the gynoecium at the top of the flower, while the rest of the parts are located lower down

simple pistil

composed of one carpel

compound pistil

composed of two or more carpels

anatropous

one in which curvature during development results in displacement of the micropyle to a position adjacent to the funiculus base; this is the most common ovule type of the angiosperms and is presumed to be ancestral

orthotropous

a type of ovule in which no curvature takes place during development; the micropyle is positioned opposite the funiculus base

campylotropous

a type of ovule in which the nucellus is bent only along the lower side

axile placentation

the placentae are located on a central column; partitions from the central column to the ovary wall create chambers (locules) that separate the placentae and attached ovaries from each other

parietal placentation

type of placentation found in compound, unilocular ovaries in which the ovules arise from placentae inserted on the wall of the locule near the sutures

central placentation

resembles axile placentation; however, the column is not connected by partitions to the ovary wall, and thus no locules are formed

basal placentation

one or more ovules are attached to the bottom of the ovary

calyx (sepals); corolla (petals); androecium (stamens); gynoecium (carpels/pistils)

basic parts of the flower

calyx (sepals)

leaf-like parts that form the outer whorl of the entire floral branch; internally similar to leaves: epidermis, mesophyll, and ramified vascular systems; maybe replaced with bracts in some species

corolla (petals)

leaf-like parts inner to the sepals and usually have other colors apart from green; internally similar in structure as the sepals

tepals

observed in orchids and some basal angiosperms; fusion of sepals and petals; petaloid in structure and function

androecium (stamens)

consists of the anther and the stalk and filament; usually contains one vascular bundle

anther

found at the tip of the stamen; divided into two lobes, with each lobe having two pollen sacs with pollen grains, some degree of differentiation of anther walls, and two vascular bundles

gynoecium (carpels/pistils)

basic unit of the female reproductive organ of the flower; a modified leaf that bears seeds on its surface; parts include: ovary, style, and stigma

ovary

seed-bearing enclosed organ; anatomic features include the epidermis, ground tissue, and vascular tissues in characteristic position; divided into cavities called locules

locules

cavities within the ovary; houses the ovules attached to the placenta

ovules

develops into the seed; found within the locules of the ovary and attached to the placenta

placentation

the arrangement and attachment of ovules within the plant's ovary; variable among species

style

stalk of the carpel/pistil

stigma

at the type of the pistil; surface for pollen growth

spikelet

units attached to the rachis of an inflorescence; usually bears one or more florets (depending on the species)

floret

consists of the stamens and the pistil bounded on the outside by lodicules

lodicules

small, scale-like perianth segments surround stamens and the pistil in a floret

stamens

usually differentiated into a long and slender filament with four-lobed anther

palea and lemma

bract and bracteole respectively; both boat-shaped and surround the whole floret on the outside, with the latter being the outermost

glumes

bract-like scales, usually a pair of them, that are present outside of the palea and lemma; usually empty

caryopsis

the fruit that develops within the floret, bearing a single exalbuminous seed

exalbuminous seed

seeds that have no endosperm or have completely consumed their endosperm during embryo development

pedicel

attaches the flower to the stem; usually subtended by bracts (epicalyx)

epicalyx (bracts)

a whorl of bracts that surrounds the calyx of a flower, forming an extra calyx-like structure; subtends the pedicel

apical meristem

from where the flowers develop; ceases to produce foliage leaves and instead shift from indeterminate to a determinate growth

flower primordium

the formation of small buds at the end of roots, from which a flower will grow or develop; will start from periclinal divisions of the meristematic tissue in shoot apex and later proceed by more divisions (including anticlinal divisions)

w.m. flower Tomato (L. esculentumI)

identify the specimen

Hibiscus rosa sinensis

Malvaceae; gumamela

Nymphaea nouchali

Nymphaeaceae; water lily

Annona squamosa

Annonaceae; atis/sugar apple

Cosmos caudatus

Asteraceae; cosmos

Jatropha pandurifolia

Euphorbiaceae; peregrina/jatropa

Orchidaceae

family of orchids

Zea mays

Poaceae; corn

gymnoecium

site of embryo sac development; two major processes: megasporogenesis and megametogenesis

megasporogenesis

the development of megaspores from the megasporocyte, the cell that undergoes meiosis; meiosis of the megasporocyte nucleus results in the formation of four haploid megaspore nuclei

megasporocyte

a diploid cell in plants in which meiosis will occur, resulting in the production of four haploid megaspores

megagametogenesis

the process of maturation of the female gametophyte, or megagametophyte, in plants

megagametophyte

multicellular structures that develop inside the megaspore wall

x-s ovary Lily

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Embryo sac 4-nucleate Lilium

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pollen

develop inside the microsporangium or pollen sacs which enclose the sporogenous tissue which subsequently under meiosis (microsporogenesis) resulting into tetrads

microsporangium

also called pollen sacs; a sporangium that produces microspores that give rise to male gametophytes when they germinate

tetrad

becomes a microspore, which will undergo gametogenesis and transforms into either a binucleate or trinucleate structure that becomes functional pollen

palynology

the study of the external features of the pollen

microscoporogenesis

begins with the cells (microsporocytes/pollen mother cells) making up the sporogenous tissue found inside each pollen sac on the anther of a flower

tapetum cells

surround the microsporocytes; form the inner layer of the pollen sac wall

successive cytokinesis

a type of cytokinesis that occurs in angiosperms, where the cytoplasm is divided after each meiotic division; the cytoplasm is successively partitioned after each meiotic division

simultaneous cytokinesis

no wall is formed after meiosis II, the four daughter cells will be separated by phragmoplasts which will later become part of the pollen wall

microspore

composed of a large nucleus, large vacuole, and some cytoplasmic organelles

tryphine

a structure formed from the condensed cytoplasmic contents of the broken-down tapetum; deposited on the pollen grains as a coat

microgametogenesis

the process in plant reproduction where a microgametophyte develops in a pollen grain to the three-celled stage of its development

vegetative nuclei

direct the operations of the growing structure

generative nuclei

can be thought of as two nonmotile sperm cells

x-s anther Lily (telophase)

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x-s mature pollen in anther Lilium

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exine

outer wall of a mature pollen grain

intine

inner wall of a mature pollen grain

apertures

pores along the thin areas of the exine

porate

pollen with rounded aperture

colpate

pollen with furrow-like aperture

uniaperturate/monosulcate

pollen with one aperture only; observed in monocots

tricolpate/tricolpate-derived

pollen with three or more apertures; observed in eudicots

w-m pollen grain Corn

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w-m pollen grain Lily

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w-m pollen grain Cucurbita pepo

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w-m pollen guava (Psidium guajava)

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pollen germination

occurs when pollen lands on a compatible stigma

w-m pollen germinating Lilium

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