Climate. Poster 2. Lesson Notes RAND WATER RAND WATER

Transcription

1 Climate Poster 2 Lesson Notes RAND WATER RAND WATER

2 Climate Poster Hot & Dry Cool & Damp POSTER 2 Lesson 1 PHOTOSYNTHESIS Through the process of photosynthesis, plants absorb energy from the sun and use it to make carbohydrates from carbon dioxide and water. Carbohydrates are substances used to produce sugars, starch and cellulose, which are made up of carbon, combined with hydrogen and oxygen. Plants use carbohydrates as food energy to grow stems, leaves, flowers and fruits. TRANSPIRATION PULL Carbon dioxide enters the plants from the air by way of very small openings in the leaf surface known as stomata. Carbon dioxide is absorbed through a moist membrane in the stomata. These stomata open when sun light energy is available. Water evaporates out of the moist open stomata because of the heat from the sun. This is known as TRANSPIRATION. Water then moves from the roots up the stems and into the leaves to replace this loss of water. The force that causes this to happen is called TRANSPIRATION PULL. Transpiration pull is the initiating force in the path of water in plants. Deciduous plants use less water in winter because the transpiration pull is less. (These plants have less leaves or no leaves at this time and thus less stomata.) Climate - Poster 2 - Lesson 1 - Page 1

3 People have pores in their skin, which allow them to sweat and thus to keep cool. These pores are similar to the stomata in the leaf because water is lost through them. Transpiration in turn also helps the plant to keep cool. Transpiration and perspiration assist in circulation and cooling processes. Through the process of transpiration and photosynthesis plants provide: Animals with oxygen (a by product of photosynthesis). Clean air by removing carbon dioxide (during photosynthesis). Water vapour for the water cycle (water loss during transpiration). OSMOSIS Osmosis is the process that allows water to move from the soil, through plant root membranes and into the root system for transportation to the rest of the plant (transportation pull). Osmosis occurs because the plant roots have a higher concentration of nutrients and elements than the soil. If we apply too much fertilizer to the soil we burn the plant roots. What happens is there are then more nutrients and elements (salts) in the soil than in the roots and this causes water to move from the roots back to the soil through the plant membrane. This is called ex-osmisis DID YOU KNOW? Larger leaf surfaces have more stomata. The hotter the day, the more water evaporates out of the stomata during transpiration. Stomata generally do not open when the sun is not shining. This is because the sun s energy is needed to turn the carbon into sugar during photosynthesis. ACTIVITY Notes Place a plastic bag over actively growing leaves. Rub vaseline on the top of leaves. Place in plastic bag over actively growing leaves. Rub vaseline on bottom of leaves. Place plastic bag over actively growing leaves. Note how much water is transpired into the bag in one day, from the 3 different experiments. For experiment to be seen clearly, place same amount of leaves into each bag. Do not remove leaves from plant. Climate - Poster 2 - Lesson 1 - Page 2

4 SA Rainfall Pattern LIMPOPO NORTH WEST MPUMALANGA GAUTENG FREE STATE KWAZULU NATAL NORTHERN CAPE LESOTHO WESTERN CAPE EASTERN CAPE Winter Rainfall Rain all year Summer Rainfall POSTER 2 Lesson 2 LOCAL CLIMATES - SA MAP Weather At any given time at any place on the Earth, the lower environment has a particular set of properties or qualities, namely: temperature, air pressure, humidity, precipitation (rain), sunlight, cloud cover, wind speed and wind direction. The short-term properties of the environment are described as the weather of the area. Climate Climate, on the other hand, is concerned with the average, long-term weather of an area. Climate describes the region s general weather patterns, seasonal variations, and weather extremes (such as drought or floods) averaged over a long time period of at least 30 years. The two most important climatic factors of an area are temperature and precipitation (rain, hail and snow). These two factors determine the type of plants that can grow in an area, e.g. succulents in a dry climate. Climate - Poster 2 - Lesson 2 - Page 1

5 World s Climate World s Vegetaion Climate - Poster 2 - Lesson 2 - Page 2

6 World s Rainfall Macroclimates Climate can be studied at different scales. Macroclimates are climates of large areas such as a village, town or district. The way in which the heat of the sun, and the water on the planet are distributed around the Earth will decide the macroclimates. The movement of heat and water are affected by: global patterns of air circulation, ocean currents, and geographical features such as mountains. We can identify a few trends in macroclimates. Temperatures decrease as we move from the equator to the poles. Temperature also decreases with increased altitude or height. The tops of mountains are colder than their bases. Ocean currents flowing from the poles to the equator are cold and cause cool dry conditions along the nearby coast. Warm ocean currents bring heat from the equator. The warm ocean currents warm up the air above them. This warm air rises to form rain, which makes the coast warm and wet. The main climatic regions of the Earth include: (1) the equatorial belt situated along the equator which is hot and wet; (2) the tropics, which extend to 30 degrees both north and south of the equator and are also hot and moist; (3) the temperate regions between 30 degrees and 60 degrees in both the northern and southern hemispheres, which experience mild climates with few extremes; and (4) the polar regions which are cold and dry. Climate - Poster 2 - Lesson 2 - Page 3

7 Some things that affect microclimate Temperature Water Shade trees can lower the temperature of a garden. Water reflects light and therefore will have a cooling effect on the air around it. Slope Plants that need more water should be planted at the bottom of a slope, where the rainfall will collect. Wind Sunlight, shade and position of the house: The north facing side of the building will be warm and sunny, while the southern side will be cool and shady. Surfaces Big trees or hedges are often necessary for protecting garden plants against wind and frost. Dark, smooth surfaces, such as tarred areas will absorb heat and light coloured or rough surfaces such as lawn or cement paving will reflect heat. Microclimates Small variations in climate at the local level are called microclimates. For example, mountains interrupt the flow of prevailing winds and also produce a rain shadow effect on their lee-side. Large clusters of trees break up the wind and increase the local humidity. Buildings and cities alter wind speed and direction, and also increase temperatures. This is because bricks and concrete first absorb and then radiate a great deal of heat. We experience these same changes in microclimate in our gardens and at school. Understanding microclimates allows the Water Wise gardener to plan and design his/her garden so as to create microclimates that suit the plants, reducing the loss of water from the garden. Examples are: planting hedges and groups of plants to create windbreaks to reduce the effect of hot dry winds blowing into the site; reducing white reflective north-facing walls will reduce the temperature and evaporation rates from the hot north side of the garden; planting big hardy trees and shrubs to make shade will create cool areas for shade-loving plants; encouraging climbing plants to grow up frames and shade the north side of the house will cool and shade the area; and channeling runoff from a slope towards a group of thirsty plants will increase the water supply to plants that need it. Plant deciduous trees on the Northern side of the house. This will provide shade in summer and allow sun in winter to warm up the house. Most importantly, Water Wise gardeners should try to create gardens that match the natural climate of the area. Climate - Poster 2 - Lesson 2 - Page 4

8 Climate Poster Hot & Dry Cool & Damp POSTER 2 Lesson 3 PLANT ADAPTATIONS TO HOT DRY POSITIONS Oil glands in the leaf reduce evaporation : Crush and smell the leaf of a plant with aromatic oils, e.g. a Lavender or Rosemary leaf. These plants come from the dry areas of the Mediterranean and Southern Europe. Oil evaporates from these glands and remains above the surface of the leaf. This oil reduces the evaporation of water in the same way as would oil on water in an experiment. Similarly, when you dip your finger in a volatile oil and another in water, you will feel a greater cooling affect as the oil evaporates faster than water, causing a greater cooling effect as more heat energy is lost. Other common example of plants with volatile oil glands are geraniums and aromatic herbs such as lemon grass and thyme. Some come from the Mediterranean region where summers are hot and dry. Local examples can be found among the Fynbos plants of the Cape. Look just above the surface of these leaves on a very hot day, and you will be able to see a haze caused by the evaporating volatile oils. Climate - Poster 2 - Lesson 3 - Page 1

9 Light colours reflect light, cooling the leaf surface and reducing evaporation: Dark colours absorb heat, thus controlling the temperature on the leaf surface. Think about this! Are you cooler in a black shirt or a white shirt. Find a dark surface and a light surface that are both in the sun. Which one feels cooler? Leaves which are pale green or grey-green are cooler than leaves which are dark green. One example is the lavender bush, which is grey. Other plants have a pale undersurface, e.g. Wild Sage (Buddleja) and Wild Olive (Olea). These plants turn their leaves upwards in hot weather so that the pale grey undersurface reflects the sun s heat away from the plant. Leaf hairs reduce evaporation: Expose your skin to the sun. Then cover it with a cloth and feel how much cooler it is. This is how the hairs on the leaf shade the surface and thereby reduce the surface temperature of the leaf and so reduce transpiration. Think of a baldheaded man. Does his head sunburn more quickly than a man with thick hair? The hair on your head is just like the hair on a leaf. A common example of a plant with hairy leaves is Lamb s Ear (see poster). A waxy cuticle reduces evaporation : Water is also lost from the surface of the leaf between the stomata. If this surface is covered by wax, then evaporation is reduced. Look at and feel a waxy leaf. It looks shiny and it feels thick and smooth, (Example: Camelia or Aspidistra or Sanserveria). Small leaves: Small leaves have a smaller surface area for heating and fewer stomata from which water can evaporate (Example: Acacia spp or thorn trees). Sometimes leaves are reduced to needle-like structures (Example: Pine trees). Succulent leaves: Plants can store water in thick, fleshy leaves (Example: Aloe plants and succulents ). This fleshy substance in the leaves also aids the plant to moderate the leaf temperature. Stomata concentrated on the underside of leaves: Stomata on the underside of leaves are less exposed to the sun and wind and this reduces transpiration (Example: Pineapple). Deep roots: Deep roots can find water deep in the soil (Example: Fig tree, Camel thorn tree). Camel thorn tree grows well in dry areas of the Northern Cape. Succulent roots and stems: Thick succulent roots and stems store water during dry periods (Example: Iris, Agapanthus). Plants growing in shade often have spongy root adaptations. Climate - Poster 2 - Lesson 3 - Page 2

10 Life cycle strategies for surviving dry periods: Annual plants: Annuals have short life-spans that are completed in one year. They grow, flower and produce seeds during the favorable periods and then survive dry periods by producing tough dormant seeds (Example: Namaqualand daisies and Marigolds). Bulbous plants: Lose all their above ground parts and lie dormant underground as bulbs during their non-growing period (Example: Daffodil, Tulip and Nerine). Deciduous plants: Lose their leaves during the cold dry season to eliminate transpiration and remain dormant until spring (Example: Stink wood, Oaks, Combretum species). A rough leaf surface is cooler than a smooth one: A rough surface heats up less than a smooth surface. To test this find an uneven surface like a rough gravel road. Compare it to a smooth surface. To make it a fair test, both surfaces must be the same colour and in a similar position (exposure to sunlight). Examples of this kind of plant are Buddleja and Sage. Did you know more information can be obtained by contacting Rand Water on or visiting Rand Water's Water Wise web-site : ACTIVITY Notes Walk around the garden (school grounds) collecting different plant leaves. Study them to see if they have any specific plant adaptations to hot dry conditions. (You may need to use a magnifying glass). Walk around outside and identify microclimate aspects in different areas of your school grounds. 3. Cut open a leaf of a succulent plant and compare to any other non-succulent plant. Climate - Poster 2 - Lesson 3 - Page 3

11 RAND WATER For information and ideas on Water Wise gardening call the Rand Water customer service centre on , or visit the home and garden section of their website at RAND WATER