Question

practice mini frq

1. a student wanted to study the effect of varying colors of light on the growth of plants. the student exposed tomato plants to three different wavelengths of light over the course of one week and measured the overall height of each plant daily. all other conditions were kept consistent among the plants. the results are shown below. (a) identify the wavelength of light that caused the least amount of growth in the tomato plants. (b) explain why the wavelength identified in part a was ineffective in promoting plant growth, specifically considering the role of chlorophyll and light absorption.

effect of varying wavelengths of light on tomato plants

Explanation:

• Part (a): By analyzing the graph, we can see that the line representing 550 nm has the lowest height values over the course of the week, indicating the least growth.
• Part (b): Chlorophyll, the main pigment in plants for photosynthesis, absorbs light mainly in the red (around 600 - 700 nm) and blue (around 400 - 500 nm) wavelengths. The 550 nm wavelength is in the green range. Chlorophyll reflects green light rather than absorbing it effectively. Since photosynthesis (which is crucial for plant growth) requires light absorption to convert light energy into chemical energy (glucose), the lack of absorption at 550 nm means less energy is available for the plant to grow.

Answer:

(a) 550 nm
(b) Chlorophyll reflects green - light (550 nm is in the green range) rather than absorbing it. Since photosynthesis (for growth) needs light absorption to convert light energy to chemical energy (glucose), the lack of absorption at 550 nm makes it ineffective for promoting plant growth.