Life Processes in Plants

About this chapter

Life Processes in Plants is the tenth chapter of Class 7 Curiosity. Through a series of activities by Bhaskar, Barkha didi and others, students discover how plants grow, get food, transport water and food, and respire. Activity 10.1 shows that both sunlight and water are essential — the plant in direct sunlight with water grows best; the one in darkness or without water fails. Leaves are the 'food factories' of plants because they contain the green pigment chlorophyll, which captures sunlight to prepare starch in the presence of carbon dioxide and water. The iodine test in Activity 10.2 turns the green parts of a leaf blue-black, confirming starch. Activity 10.4 with caustic soda proves carbon dioxide is essential. Activity 10.5 with a water plant under sunlight shows oxygen is released — a lit matchstick burns intensely. The process by which plants prepare food using sunlight, chlorophyll, water and carbon dioxide is called photosynthesis: Carbon dioxide + Water gives Glucose + Oxygen. Rustom Hormusji Dastur (1896-1961) of India studied photosynthesis. Tiny pores on the lower leaf surface called stomata help in gas exchange. Inside the stem, water and minerals move up through xylem; food made in leaves moves to other parts through phloem (Activity 10.7 with red ink shows this). All plant parts respire — glucose + oxygen gives carbon dioxide + water + energy — proven by lime water turning milky around germinating moong seeds (Activity 10.8). Kamala Sohonie (1911-1998) worked on plant respiration. CTET Paper 2 Science tests this chapter through word equations, the role of each raw material, xylem-vs-phloem identification, stomata function, and pedagogy of activity-based learning. The four tests — Practice 15 Q, Quiz 15 Q, Hard 15 Q, Mastery 30 Q — cover these ideas at exam depth.