Phytochrome And Pytohormone Effect On The Germination Of Lettuce Produce

Introduction

In this lab, we looked at Phytochrome and Phytohormone effects on the germination of lettuce seeds. We narrowed our experiment down to the effects that red and far-red light have on germination. Phytochromes are proteins that have a chromophore, which can either be active or inactive. Pfr (active) absorbs far red light, and Pr (inactive) absorbs red light. When a plant absorbs red light, Pr is converted to Pfr. By contrast, absorption of far-red light converts Pfr to Pr. Before the experiment, we read that lettuce seeds require light to germinate. Phytochrome was discovered by Borthwick (1952) and isolated by Butler (1959) from etiolated seedlings of maize. It causes germination of seeds, and can inhibit flowering in Short Day

After labeling, we placed dishes #1 and #2 in the red light chamber and turned on the incandescent light for 5 minutes. We set up an ice bath that acted as a heat filter. After 5 minutes of being exposed to red light, we wrapped dish #1 with aluminum foil so no other light could interfere with seed germination. By contrast, dish #2 was placed in the far-red light chamber upon completion. We also labeled dishes #3 and #4 and placed them in the far-red light chamber. As before, there was an ice bath that acted as a heat filter. These dished were exposed to fluorescent light for 15 minutes. Upon completion, dishes #2 and #3 were wrapped in aluminum foil. Dish #4 was subsequently exposed to red light for 5 minutes and wrapped with aluminum upon completion. Dish #5 was tightly wrapped with aluminum foil after labeling, as it was the Dark treatment. Dish #6 was labeled and not wrapped in aluminum foil as it acted as our light treatment. All of the dishes were taken to the culture room. After three days, we returned to the culture room and counted which seeds had the most germination. We counted the total number of seeds and the number of seeds germinated. We were then able to see which treatment had the highest percent germination by dividing the number of germinated seeds by the total number of

This is because when seeds are exposed to red light, the active form of chromoprotein known as Pfr is formed, which triggers plant growth and seed germination. The Red treatment had 43 total seeds and 17 germinated. The Red and far-red treatment had 46 total seeds and 27 total seeds germinated. The far-red treatment had 53 total seeds and had 39 seeds germinated. The Far-red and red treatment consisted of 45 total and 30 germinated seeds. The Dark treatment had the highest number of seeds with 55 but only 35 seeds germinated. Lastly, the Dark Treatment had 45 total seeds and 41 seeds germination- the highest of any treatment. This is because in order for seeds to germinate, the plant must have sufficient light and water uptake. Plants, like lettuce seeds, that undergo phytochrome-medicated seed germination, can grow better in red light as they absorb all the light available to photosynthesize