Question

1-In green plants and algae the red and blue wavelengths of light are predominantly used. Describe an experiment that can be used to test this. 100 marks

2-Describe either 1) peat bogs or 2) cloud forests and explain why they are important habitats for bryophytes. 100 marks

Answer 1

1. In the question, it is being said that green plants and algae predominantly use red and blue light. The source of light for all plants is sunlight. Sunlight is a spectrum of all the lights(VIBGYOR). When all these lights comes together, they make it look white. However, the pigment chlorophyll which are abundant in plants and whose prime function is to carry out photosynthesis has specificity towards the light spectrum. Chlorophyll absorbs the light which is usually long wavelength and appears red, or it absorbs short wavelength and appears blue. They reflect the color green, which is the reason why our eyes perceive plants as green.

EXPERIMENT

AIM OF THE EXPERIMENT

The aim of our experiment will be to make a plant grow at different setups with different wavelengths of light and make its observation.

MATERIALS REQUIRED

Plant, colored cellophane paper, pot and soil, closed boxes, watering bootle, ruler.

METHOD

1. We have to make 4 setups with plants.

2. We have to keep the plants in closed plastic boxes with ventilation

3. We have to cover the boxes with colored cellophane papers.

4. It will be covered by red paper, blue paper, green paper, and another box will not be covered at all. The box not covered is our control.

5. Observations are made over several weeks.

OBSERVATION AND RESULT

The plants are kept in the setup for several weeks and its growth is measured carefully with the help of a ruler. It was observed that the best growth occurred in the control box, ie which was not covered with cellophane paper. The growth in the red and blue boxes was fair. But the growth in the green box was not good. This shows that the plant requires all the spectrum of sunlight for its optimal growth. The wavelength of light produced by the red light is of a longer wavelength(640-680nm). It encourages the growth of a plant by boosting its flowering and fruiting ability, stem growth, etc. The wavelength of the light produced by the blue light is of shorter wavelength(430-450nm), and it helps in the growth of the root of plants, boosts photosynthesis, etc. Lastly, the green box had a negative impact on the growth because the wavelength does not match with the absorption peak of the chlorophyll and green light is reflected from the plants, Therefore, it makes sense that no light alone in itself can encourage plant growth. Together the red and blue light has a predominantly positive effect on plant growth

2. Peat bogs are an area of land which resembles a wetland. The place is largely accumulated by remnants plants like mosses which are referred to as bogs. Mosses and other non-vascular plants fall under the category of Bryophytes. Bryophytes have similarities with both aquatic plants and terrestrial plants. However, one characteristic of them is that they are highly dependent on moisture for their survival. Thus, peat bogs being a wetland provides an abundance of water supply to the mosses. Bryophytes have no issue with the acidic environment of the bog and also it thrives in the nutrient scarcity environment of the bog. Thus, it shows how peat bogs are a natural habitat of bryophytes.