Plant reproduction

• 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