Plant Reproduction - Flowering plants reproduce sexually, asexually, or both.
ASEXUAL REPRODUCTION
► Offspring are derived from a single parent without any fusion of egg and sperm
► Result is a clone that is genetically identical to its parent
Vegetative reproduction
► Asexual plant reproduction based on the vegetative growth of stems, leaves, or roots is known as vegetative reproduction.
Agamospermy
► The production of seeds without fertilization
► Embryos of agamospermy seeds are genetically identical to the parent plant
SEXUAL REPRODUCTION
► involves the transfer of male gametophytes, the pollen grains, either to the micropyle of an ovule or to the stigma of a pistil
► two major processes in sexual reproduction of seed plants are pollination and fertilization
POLLINATION
• transfer of pollen to the part of a seed plant containing the ovule
• can give an insight into the function, homology, and evolution of associated floral features
• can occur by wind, water, or animals and insects
wind pollination (anemophily) - release of enormous quantities of smaller-sized pollen compensates for the randomness of dispersal by the wind.
water pollination (hydrophily) - may occur in aquatic plants with flowers either at or under the water surface • rely on water to disperse pollen.
insect pollination (entomophily) is when insects transfer pollen from one flower to another.
bees - melittophily or hymenopterophily — bee-pollinated flowers have a delicate, sweet fragrance — often have specialized color patterns called nectar guides — ultraviolet markings that help insects locate the nectaries — bees are attracted to bright colors, primarily yellow and blue
moths - phalaenophily — moths detect odors, flowers they pollinate are often sweetly fragrant — usually white or yellow, which stand out at night when they are active — tend to have long, nectar-filled tubes or spur
butterflies - psychophily — butterflies detect odors, flowers they pollinate are often sweetly fragrant — usually bright-colored — tend to have long, nectar-filled tubes or spurs
flies - sapromyiophily — many fly-pollinated flowers are reddish, maroon or brown in color and fleshy — emit an odor like rotten meat or flesh
bats - cheiropterophily — like moth-pollinated flowers, are lightcolored and aromatic, attracting their nocturnal pollinators — stamens tend to be numerous
birds - ornithophily — usually large and bright red or yellow, but have little odor — flowers produce sugary nectar that helps meet the high energy demands of the pollinating birds — petals are often fused, forming a bent floral tube that fits the curved beak of the bird
GAMETOGENESIS - formation and development of gametes • occurs in anther and ovules
• in anther, meiosis occurs in microsporocytes to form microspores
• in ovules, meiosis occurs in megasporocytes to produce megaspores
ovule - immature seeds, technically consisting of a megasproangium enveloped by one or more integuments
identify
A) chalazal end
B) nucellus
C) micropyle
D) funiculus
E) micropylar region
F) integument
microsporangia - sites of production of pollen grain
FERTILIZATION • fusion of gametes • occurs after the two sperm reach the female gametophyte
double fertilization
► One sperm fertilizes the egg, forming the zygote.
► The other sperm combines with the two polar nuclei, forming a triploid (3n) nucleus
EMBRYOLOGY • Process of initiation and development of an embryo from a zygote which is a product of double fertilization