Unit 2: Reproductive Biology

Reproduction of Angiosperms ~ Reproduction is the process of continute continuty of lige It involves the fussion of gamets and is the production of offsprings for percennation, & con- tinuty of the species - It is of two types iy sexual reproduction Fix Asexual reproduction 94 Asexual Reproduction: Asexual reproduction involves the gussion og sporres which are morettle ore, non-mortile. It involves single parent cand produce geneti- cally individuals which are identical & coulis clones It takes place generally among lower plants, ani- gungus mars, protista, monera & Ugungus. *Asexual Reproduction takes place by various meth -ods by fragmentation, budding, & tion etc. fission, spoпища- 99) Sexual Reproduction: It involves two parcents wherre are produced by qussion of gamets. offsprings →The offsprings are not identical genetically. + teukes place in highiere plants and animals. -Ontherr * As the Bird cohorle present next to corcolla. It is the male reproductive orgen which consist of units called stamen stamen consist of fillaments, anther, lobes and connective. do diynoccium It is the 4th whorle present next to Andro- -ccium. -It is called female reproductive oregan consist of carpel units. The female structurcie is also called pistil. The carrper consist of a basal ovary, egrindini- cal style cand upper most resective paret called stigma. - The steek of the flower is called pedicle and the lear like structure bearing a slower in its anis called bract. are pre- When both androccium and дупосетит sent in a flower it is called bisexual or herrm- aphrodite Flower when y whorcies are present in a lower it && called a complete flower. *It is generally responsible fore dehiscence of maturity. anthers upon one 3% Middle layer It is the next layer inner to endothesium. It is generally 2-3 layers usinucleated, flattened and vasculated. These are ephimereal and digenercate almost comp- meiosis Lepely before the pollen mother cell undergoes rottisis. This layer is responsible fore storcing of food meter- fars, especicely stearich 90R pollen devetopement sometimes secondary thickenings in middle layer helps in anthere debisence. 4% Tapetum *It is the tonermast layer of anther present adjacent to middle layer. *It is generally single layer with dense cytoplasm & dominent nucleus. It is multinucleated and provides nutrition to the sporogeneous tissue and helps in developement of microspores. Some epidermal cells at specific site gets disan into small specialized cells that splits at centher maturity, This is called stomium. The parcientas cells upon many periclinal and anticlinal division forums 3-5 layers of epidermis 09 anther wall. The sporoginious cens directly function as mme upon mitotic division forums y tetrads (microspore). Structure of micraspore of, Pollengrain ~~ microspore is haploid single nucleus. @ unicellular body with *-Ait maturity it may be ovar, trianguleer lobed off/ cresent shaped. The microsporce has tooo layers -outer exine Thick & rough Inner intine Thin & smooth to The exine is composed of sporropollenin, a polimer of carrotinoid. * It is very tough & hard & resistant to Physical and chemical decomposition. The exine is covered by a yellowish viscous sticky substance called pollen kitt sticky The pollen kitt emits smell 1 & helps attract insects and protects the pollen from UV. The intine is composed of pectin cand cellulose. It helps in storage of starch and olis. At certain places the exine remains thin ecured gerem porre through which the intine comes outside and gorems the pollen tube. Calose deposition and it's Significance Calose is a polysaccharide made ap of B-1-3 glucan. It is synthesized and deposited into the cell surface, cell wall, and other locations within the micrcosparcocyte and megaspore during reproductive development. *Calose deposition was 1st described by mangin It is laid down at plasmodesmaza during cytokinesis and pollen development. It is produce in response to wounds, infection by 1, by touch of chemicals like aluminium and pathogens, by ABA. When any wound happens the deposition stearets tmmidiately It is also gorems by breaking the cytoplasmic conn- ection between tapetum and pollar mother cell. (PMC) *Calase deposition continues through meiosis and stops ones His givestrise tetreads. Function: It is required for development of tetreads (micro- spore & megaspore). →+ porrticipates in plant reproductive development which includes the development of male gametophyte. *These layers protect the development of micro- sporocytes from disserrent harmful, hormonal cand nutritional intuences. *It also protects the sporrocytes from distercent environmental hazards like uvrays etc. *It acts as a temporcarry physical barction to prevent premature swelling & brusting of micrraspore. *Lack of carose deposition leads mare sterility → Calose deposition helps in foremation of thick exine whase absence leads thin cell well gorema- tion Lastly it is a serective barercion or molecular Filtere conich allows certain macromolecules to enterr inside the pollen greains.