Highest Rate Of Germination In Lettuce Seeds example essay topic

7 TH Form Biology Plant Investigation Contents 1. Abstract 2. Background Information 3. Aim / Hypothesis/Variables 4. Method 6. Results 7.

Graphs 9. Conclusion Background Information Lettuce 'Lactuca sativa Continental Looseleaf Frisby' How to grow Lettuce Lettuce is fast growing and is one of the few vegetables that can grow almost all year round. Lettuces can rarely be over watered. Sometimes the seeds need to be refrigerated for them to germinate effectively. Lettuce seeds germinate better in cool soils and will become dormant in soil temperature of 25 C and above.

You can begin to sow seeds of cold tolerant varieties about four weeks before the last expected frosts. Sprinkle the seeds onto the top of the soil, either directly into the vegetable garden or in a starting tray, and cover lightly with soil. Dampen the soil and remember to keep the new seedlings and later the plants moist- lettuce needs moisture throughout the growing season. Lettuce and Light In lettuce seeds, a critical step in triggering seed germination is photo activation.

The seeds need to be exposed to light in order to germinate. The wavelength of light is critical. The seeds germinate well in white light, but also to single "colours" particularly red light. On the other hand, far-red light strongly reduces lettuce germination. It took a long time to identify, isolate, and characterize the photoreceptor.

It is called phytochrome. Phytochrome exists in two different chemical forms: Pr and Pfr. Phytochrome in its Pr form absorbs light maximally in red wavelengths. Phytochrome in its Pfr form absorbs light maximally in far-red wavelengths. What made characterizing phytochrome difficult was the fact that the two forms inter convert.

As Pfr absorbs far-red light, it changes chemically into Pr! Similarly, Pr absorbs red light and changes chemically into Pfr. Back to the lettuce, obviously the garden problem is planting the seeds too deep (in the dark! ). Without light to photo activate seed germination, the seeds fail to germinate to their potential. In the dark, the ratio of Pfr to Pr determines whether each seed will germinate.

If exposed to red light, the phytochrome is all converted into Pfr and the seeds germinate. When the seeds are exposed to far-red light, the phytochrome is all converted into Pr and the seeds fail to germinate. Obviously the active form of phytochrome is Pfr. Aim To find out which colour (out of: Green, Red and Blue) light, will produce the highest rate of germination in Lettuce seeds. Hypothesis That the Lettuce seeds under red light will produce the highest rate of germination Null Hypothesis That red light will not produce the highest rate of germination in Lettuce seeds. Variables Variables I will manipulate: Colour of light.

Variables I will control: No. of seeds Amount of water Time allowed for germination Amount of cotton wool Variables I cannot control, but will be the same for all for all the seeds used in this experiment: Temperature Amount of light Equipment. 12 Petri Dishes Circumference = 27 cm. Water. Cellophane - Red - Green - Blue - Clear. 4 Boxes measuring 35.5 cm X 24 cm X 8 cm.

Lettuce Seeds. Cotton Wool. Mister Bottle Method 1. Cut out 25.5 cm X 16 cm rectangle from centre of lid of lid of each box. 2. Sellotape Cellophane to inside of lid ensuring cut out area is completely covered 3.

Roll out Sheet of Cotton wool and Cut out 12 circles, using a Petri dish to measure 4. Place a cotton wool circle in each Petri dish 5. Dampen the cotton wool with 10 mills of water in each one 6. Place 20 Lettuce seeds in each Petri dish on the cotton wool (roughly 1 cm apart) 7. Place 3 Petri dishes inside each box and close lid 8. Place boxes in a relatively sunny place inside 9.

Use Mister bottle to spray 2 mL (two spritzes) of water on each... Petri dish every day at 5.30 pm to keep cotton wool damp. 10. Every day at 5.30 pm count the number of germinated seeds 11. Record results every day, until one Petri Dish Reaches 100% Results Graphs Conclusion That the Lettuce seeds under red light will produce the highest rate of germination, This Hypothesis was proved correct, as is shown by the mean total germination percentage..