sexual reproduction_flowering plants

8/13/2019 Sexual Reproduction_Flowering Plants

1/8

Name: Class

Sexual Reproduction in Flowering PlantsInvestigation 12. 1 o examine an insect-pollinated flower e.g. Clitoria

Apparatus andMateriaIs

Procedure1. Examine, draw and label the external features of the flower.

xternal features of floweragnification = X

2. ut the flower longitudinally into two halves. To do this, carry out the followinginstructions.(a) ut off half the standard petal (the largest petal).(b) Remove one wing petal from the same side. You will now see two greenish-yellow keel petals.


2/8

ovary

(c) Remove one keel petal from the same side. You can now see the stamentrough, which encloses the ovary, 9 anthers at the end of the stamen trough, afree stamen (i.e. not fused with the trough), a stigma and a portion of the style.

stamen trough style; r v o y ~ rtigmaree stamen stigmaFig 12.1 Fig 12.2

(d) ut the stamen trough lengthwise to reveal the pistil (or gynoecium). Takecare not to damage the pistil.(e) Very carefully cut the ovary lengthwise to reveal the ovules inside it.

3. Examine the base of the stamen trough. You may find some sticky, sugary fluid in it.This is nectar.4. Make a large, labelled drawing of the half flower. Label the following structures:pedicel (flower stalk), calyx, standard petal, nectar guides, wing petal, keel petal,

stamen trough, filament, anther, free stamen, ovary, ovules, style, stigma.

h lf flower


3/8

5. Remove a few anthers. Examine them under a microscope. Note the size, shape andthe surfaces of the pollen grains. Examine also the pollen grains of Hibiscus underthe microscope. Make a drawing of one pollen grain from each flower.

Clitoria pollen grain Hibiscus pollen grain

6. Does the pollen grain have a smooth or rough surface?

7. List out 4 features to show that the flower is adapted to insect pollination.a)(b)c)

8. Examine the fruit of Clitoria Split it into 2 halves. ake a labelled drawing of onehalf of the fruit.

One h lf of Clitoria fruit


4/8

9. Changes take place in the flower during fruit formation. Complete the followingtable to show the changes that take place during fruit formation. Draw a line tomatch each structure with the correct function in the right hand column the firstexample has been done for you.

Flower partpetals

sepals

ovary

ovule

style

stigma

stamens

ovary wall

Changes during fruit formationfruit

seeds

wither and fall off

only part of it remains

may persist in the fruit

pericarp

wither and fall off

wither and fall off


5/8

Name: ClassInvestigation 12 2 o examine a wind pollinated flower(StudyChapter 20ofyour textbookbeforeyou proceedwith thisinvestigation.)

pparatus and Materials grassinflorescences,e.g. acoverslipIschaemum muticum arazor blade ahand lens forceps amicroscope amounted needle aglassslide asmall pieceof blackpaper

Procedure1. Examinean inflorescenceofIschaemllm such astheonesshown inFig12.3.Note:(a) thelarge,featherystigmasprotruding out of thebracts,

(b) the stamens have long,slender pendulous filamentsthathang outside thebractsexposing the anthers tothe wind. Theanthers shakeeasilyupon theslightestbreeze.

Fig 12.3Two inflorescences of Ischaemum Fig 12.4 p ir of spike ets2. Carefullyseparate the inflorescenceby using apair offorceps.You would be abletofindspikeletsoccurringin pairs such asinFig.12.4.3. Of the pair ofspikelets,one(usuallythe lower spikelet)isbiggerthan theother.Usingforceps,very carefullyspread open the spikeletsothat you have something

that lookslikeFig.12.5below.

Fig 12.5 spikelet opened up


6/8

The spikelet you have spread open consists of 2 flowers. Note how small the flowers are.One flower has 3 stamens only while the other has both stamens and pistil.4. Carefully remove the bracts leaf-like structures). Take out the pistil and thestamens. Place them on a piece of black paper. Examine them with a hand lens.

Make a large, labelled drawing of one stamen and the pistil. Label the following:ovary, styles, stigmas, filament, anther.

Stamen PistilMagnification = X Magnification = X

5. rush open the anthers on a glass slide or dust some pollen onto the slide. Examinethe pollen grains under the microscope. Make a large drawing of one pollen grain.

pollen grain6. ompare the size of this pollen grain with the ones you have seen in the insectpollinated flower in Investigation 12.1. Which pollen gra in is biggest?

7. Observe the pollen grain again. Does t have a smooth or rough surface?

8. List out 3 features that show that the flower is adapted to wind pollination.a)b)c)


7/8

Investigation 12.3 Question from Singapore-Cambridge GCE 0 LevelScience Practical Examination November 1984"'-- "-'

~ ~ p a t a t u s and Materials .\',:,':


8/8

(c) Remove the petals carefully, leaving the remainder of the flower intact. Examinewhat is left of 51 and make a large labelled drawing of this specimen as seen from aside view. State the magnification of your drawing.

agnification = X(d) Complete the following table to indicate the parts of the complete flower that will be

present in the mature fruit. For each part named state the changes that take placeduring fruit formation.

Part name Changes taking place in fruit formation

(e) In natural conditions, flowers like 51 grow together in large bunches, or many growclose together in a spike on one tall common stalk. How does this aid their chancesof pollination?

sexual reproduction_flowering plants

Documents