Settler Describe the pathways and mechanisms by which water passes from the soil to the xylem vessels in the root. [6]

Module 3 Exchange and transport 9.5 Reducing water loss

Starter Stomata must be open during the day for photosynthesis, so carbon dioxide can enter and oxygen can leave. Water is lost by transpiration from the leaves Write down one way plants reduce water loss Discuss Student to write down on post it and stick on board, discuss, page 78

Learning Objectives Success Criteria To understand xerophytes (cacti and marram grass) and understand how they are adapted to reduce water loss To be able to understand how specific plants are adapted Define the term xerophyte and hydrophyte (Grade D – C) Describe the adaptations of plants to the availability of water in their environment (Grade C –B) Explain how xerophytes and hydrophytes are adapted to their environment (Grade B – A)

A plant adapted to living in a dry arid habitat; a desert plant Xerophyte A plant adapted to living in a dry arid habitat; a desert plant Define the term xerophyte (Grade D – C)

Independent learning feedback Students to feedback one of their Choose at least 1 of their xerophytes and identify all their adaptations to living in arid/dry conditions Complete exam questions Explain how xerophytes and hydrophytes are adapted to their environment (Grade A – B)

Hydrophytes Plants that live in water (submerged, on the surface or at the edges of bodies of water) need adaptations to cope with growing in water or a permanently saturated soil. Examples include – water lilies, water cress, duckweeds and yellow iris. On your post its write down examples of adaptations

Hydrophyte adaptations Wide, flat leaves that spread across the surface of the water to capture as much light Very thin or no waxy cuticle, there is no need to conserve water Open stomata on upper surface of leaves, guard cells are inactive. Water supports leaves and flowers so no need for strong supportive structures Small roots, as water can diffuse directly into stem and leaves Large surface area of stems and roots under water Air sacs to enable floating on the water Aerenchyma – specialised parenchyma (packing) tissue forms in the leaves, stems and roots. This makes them more buoyant and a low resistance internal pathway for oxygen to the tissues, in low oxygen conditions (anoxic) In mangrove swamps where there is excess water, aerial roots such as pneumatophores grow upwards in air with lenticels

Plenary Xerophytes are plants living in desert habitats where the conditions are very ……………. . Their leaves show a variety of modifications to ……………….. transpiration. Many have a thick ……………… cuticle. Their leaves may be covered with hairs which trap ……………. ……………. . In some, the leaves are in the form of needles which reduces their surface area. Their ……………. are often sunken into pits in the surface of the leaf or stem. [5]

SA – show of hands