Chapter 7: Adaptations of Plants in Different Habitats

7.1 Adaptations of Plants

• Adaptation is the adjustment of an organism to its environment to ensure survival. (p.134)
• Plants are classified by habitat into mesophytes, hydrophytes, halophytes and xerophytes. (p.134)
• Mesophytes live in habitats that are neither too dry nor too wet, e.g. mango, hibiscus and rubber trees. (p.135)
• Xerophytes live in hot, dry habitats such as deserts, e.g. cactus and date palm. (p.135)
• Halophytes live in saline swamps where salt is high and oxygen is low, e.g. mangrove trees. (p.135)
• Hydrophytes live on or in water, e.g. lotus and Elodea sp. (p.135)
• Halophyte leaves have thick cuticles and sunken stomata to reduce transpiration, succulent tissue to store water, and hydathodes to remove excess salt. (p.136)
• Halophyte roots branch widely for support in soft mud; pneumatophores grow upwards for gas exchange through lenticels. (p.136)
• Mangrove root cell sap has a higher salt content than seawater, so roots receive water and minerals from seawater without losing water. (p.136)
• Hydrophytes have fibrous roots and trap air bubbles, which keep them light and stable in water. (p.136)
• Floating hydrophytes such as lotus have broad, thin leaves with stomata on the upper epidermis and aerenchyma tissue with air spaces in the stem. (p.137)
• Submerged hydrophytes such as Elodea sp. have thin, small leaves without stomata or waxy cuticle, and small hollow stems that help them float upright. (p.137)
• Xerophyte roots grow widely and deep to absorb water, which is stored in roots, stems and leaves. (p.138)
• Xerophytes have small leaves, thick waxy cuticle, leaves modified into thorns that reduce water loss, and sunken stomata. (p.138)
• Cactus stems carry out photosynthesis, and thorns help collect dew and deter herbivores. (p.138)