HORTICULTURE 101 READING GUIDE
LIGHT AND PLANT GROWTH – Chapter 5
1) Pigments are molecules that absorb light. What four types of pigments are present in
chloroplasts? Which is directly involved in photosynthesis and which are “accessory” pigments?
What are accessory pigments?
2) Which portions of the electromagnetic spectrum are considered “photosynthetically-active”?
Are all wavelengths of light within this range utilized (absorbed) to an equivalent degree during
photosynthesis? Please explain. (HINT: See Figure 5-4).
3) What is unique about the process of photosynthesis in plants exhibiting crassulacean acid
metabolism, termed CAM plants. When is carbon dioxide absorbed and what are the chemical
products of this initial fixation reaction? When are carbohydrates synthesized by photosynthesis
(day or night)? How do these metabolic adaptations facilitate water conservation?
4) Plants that are grown in the dark for a sufficient length of time to induce changes in their
phenotype are said to be ‘etiolated’. What ‘symptoms’ are characteristic of the etiolated
condition?
