Final answer:
Mitochondria are present in photosynthetic tissues to provide ATP for cellular processes, not just for photosynthesis. This ensures plants have energy at all times, as mitochondria produce ATP through cellular respiration using glucose from photosynthesis.
Step-by-step explanation:
Mitochondria are observed in plant cells that contain chloroplasts because they provide energy for various cellular processes. While chloroplasts carry out photosynthesis during the day, converting light energy into glucose, mitochondria are responsible for producing adenosine triphosphate (ATP), the cell's main energy-carrying molecule, through cellular respiration. Even photosynthetic cells require ATP for activities other than photosynthesis, and this ATP is produced by the mitochondria using the glucose generated by the chloroplasts.
Plants need both photosynthesis and respiration to conduct metabolic processes during both light and dark times, which is why plant cells contain both chloroplasts for photosynthesis and mitochondria for cellular respiration. This ensures a continuous supply of ATP, regardless of the availability of sunlight. Overall, the presence of mitochondria in photosynthetic tissue underscores the relationship between photosynthesis and cellular respiration in energy production.