BIOLOGY FORM 3 REPRODUCTION IN PLANTS Sub Topic

BIOLOGY FORM 3

REPRODUCTION IN PLANTS

Sub Topic : Double Fertilization in flowering plants.

Lesson Objectives: By the end of the lesson the learner should be able to:

i) Draw and label the structure of both Mature pollen grain and Mature embryo Sac. ii) Describe the process of “Double fertilization “in flowering plants. iii)State the events that occur to floral parts of a flower after fertilization.

Observe the photo below :

Answer the following questions based on the photo.

a)Name different floral parts of the flower b)Identify the part that contain the: i) Male gamete ii) Female gamete

Correct responses a)- Sepals ( Calyx) - Petals ( Corolla) - Male parts ( Androecium) - Female Parts ( Gynoecium )

b)- Pollen grain - Ovary

Observe the clip below : http: //int. search. myway. com/search/video. jhtml? searchfor=double+fertilization+simulation&n=7839 e 7 c 4&p 2=%5 EH J%5 Exdm 659%5 ETTAB 02%5 Eke&ptb=8 A 1066 B 0 -0319 -4 E 23 -8 FB 4 F 885 E 587 DDFC&qs=&si=CICE 1 q 2 wrt. QCFSEW 0 wod. Z 3 QEe. Q&ss=sub&st=hp&trs=wtt&tpr=ss-hs&ts=1500445941790

Questions a) What process does the simulation demonstrate in plants? b) Draw and label the parts the structure where the above process occur. c) Give the definition of the above identified in a) above d) State the events that occur after the above process

Expected Responses a) b) Double fertilization Mature Pollen grain

Mature Pollen Grain

Mature Embryo sac

Defination of Double fertilization

Process occurring in flowering plants in the embryo sac (Ovary) where one of the male nuclei fertilizes the egg to form diploid zygote that later develops into embryo while the remaining male fertilizes the polar nuclei to form triploid nucleus that later develops into endosperm.

Process of double Fertilization

Double Fertilization Process in Details Pollen grain falls on the stigma and absorbs nutrients from the stigma to form a pollen grain tube. The Pollen grain tube has the tube nucleus and Generative Nucleus. The pollen tube grows down the style to the embryo sac taking along male nuclei with it. The pollen tube gets nourishment from the surrounding tissues of the style. The process is quite rapid(fast) As the pollen tube grows down the style the tube nucleus leads the generative nucleus follows. Along the way the generative nucleus divide mitotically to form two male nuclei.

Pollen tube enters the ovule through the Micropyle and penetrates the wall of the embryo sac and burst open. The tube nucleus disintegrates giving way for the entry of male nuclei. One of the male nuclei fuses with the egg cell to form a diploid zygote which develops into embryo while the other male nucleus fuses with the Polar nuclei to form triploid nucleus… this Double Fertilisation.

What happens to the flower after fertilization Sepals dries and falls off/persists. Petals and stamens wither and fall off. Ovules become seeds

Ovary becomes fruit Diploid zygote develops into embryo Triploid nucleus develops into endosperm

Task: State the role(s) of the following: a) Synegids b) Antipodal cells c) Integuments

End of lesson The Future is Bright with Science

Bye

By Omboga Wilfred Kingoina (OWK) Thank You