4 investigate the effects of sucrose conc on pollen tubes

how does the pollen grain get down to fertilised the embryo

The pollen tube is a path digested through the stigma of a plant by hydrolytic enzymes so the pollen grains can travel down the stigma and through the micropyle to the embryo sac and eventually to the ovum for fertilisation. The production of these enzymes is catalysed by the pollen tube nucleus in the pollen grain

explain the method to investigate the effects of sucrose conc on pollen tube growth

1. dilute the stock sucrose solution to several set concentrations eg 1,0.8, 0.6, 0.4, 0.2

2. place a moist piece of filter paper into a petri dish to form a humid chamber

3. put a few drops of sucrose solution and an equal volume of minerals slat medium onto a clean microscopes slide

4. Use a mounted needle to rub the anther of the flowers so they shed some pollen onto the microscopes slide. Don’t add a cover slip to prevent the conditions becoming anoxic.

5. Place the slides into the petri dish until it is time to observe the,

6. start the stop clock. place the slides under the microscope and use a calibrated eyepiece graticule to measure the pollen tube

conclusion

As sucrose conc increases mean pollen tube growth also increases up to an optimum. after this point as sucrose conc increases mean pollen tube growth decreases. This is because of the osmotic effects of increasing con of sucrose.

what are some of the hazards of this experiment

biohazard allergies soil bacteria contamination = safety precaution wash hands after practical’s

cuts from sharp objects take care when handling glass objects keep away from edge of desk= elevates cuts apply pressure do not remove glass from wound seek medical assistance

scalpel cuts from sharp objects =cuts away from fingers uses forceps to hold sample whilst cutting