Presentation pbl by chinchilla

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  • 1. TBF 3023Plant Physiology PBL- WHEN NATURE STRIKES Group members: Wong Siew ChingD20091034815 Chew Mei Ping D20091034816 Ong Shwu Chyn D20091034817 Yee Hon Kit D20091034822 Ngang Huey Chi D20091034861

2. HOW CACTUS AND BROMELIADS CAN GROW WELL UNDER DRY CONDITION? 3. Cacti -most water-resourceful plants in the world Pineapple- highly tolerant of drought. Drought tolerant refers to the degree to which a plant is adapted to arid or drought conditions. drought tolerant plants typically make use of either C4 carbon fixation / crassulacean acis metabolism (CAM) to fix carbon during photosynthesis. Both cactus and bromeliads are CAM plants. 4. WHAT ARE THE CHARACTERISTIC OF CACTUS AND BROMELIADS? 5. THE CHARACTERISTICS THAT HELP THEM TO SURVIVEIN DROUGHT.Cactuses CriteriaBromeliads Leaves on most cacti areLeaves ~The epidermis of leaf is absent or extremely tiny especially thick and toughto resist damage anddesiccation.~A special layer of waterstorage cells on theunderside of the leaf thatact as a reserve in timesof water stress~have tiny scales on theirleaves called trichomes.The cactus stem serves Stem Have distinctive, water- as the plant's main absorbing scales . Their photosynthetic organ and thinness and large is used for water storagesurface area make thescales ideal for rapidly absorbing water. 6. CactusesCriteriaBromeliadsCactus roots help to RootsAble to resist wilting gather and preserve water in several ways . open their stomates at StomataOpens its stomata during night rather than duringthe night rather than the the day in hot or dry daytime climates(CAM Photosynthesis) (CAM Photosynthesis)SpinesOthers Xerophytes Skin 7. BROMELIADS LEAVES Unique shape and arrangement of the leaves of bromeliads. Wide and deeply U-shaped where they join the stem, forminga series of vessel-like compartments. When it rains, water flows down the leaves and pools in thecompartments, where it can be absorbed by the umbrellascales. Remarkable "tank plants" - Nidularium and Billbergia. Greatly reduced stem & densely packed leaves have broad, overlapping bases, resulting in a pitcher or vase- like center-the tank. Rainwater fills the tank ,as the tank is shaded by the dense crown of leaves around it, the water does not evaporate quickly and can persist, enabling the plant to survive periods of drought 8. CACTUSES ROOTS Shallow & extensive root systems Spread laterally away from the plant. Maximize water intake from a large area. Change characteristics as the water supply fluctuates. Existing dehydrated roots become more water conductive after rainfall. Formation of new rain roots to help soak up water. In times of drought, the rain roots shrivel and fall off .The existing roots dehydrate. The shrinkage of the existing roots creates an air gap that helps to prevent water in the roots from escaping back to the soil. A corky layer on the roots also helps to prevent water loss. 9. SPINES OF CACTUS Spines help the cactus in several ways. Protection against foragers. Water from dew condenses on spines and, in some cactus species, downward-pointing spines help to direct rainwater to the roots of the plant. Reflect light away from the cactus stem theoretically lowering the stem temperature. Trap in a layer of air next to the cactus stem preventing loss of water via evaporative cooling. 10. SKIN OF CACTUS Translucent & acts as the first line of defense against fungi, bacteria, and foraging animals. The skin has two parts: the epidermis and the hypodermis. The skin's hypodermis layer provides mechanical support for the plant. A waxy layer of cells known as the cuticle covers the skins epidermis. The wax in the cuticle helps the stem to hold in its water vapor reducing water loss. Waxy cuticle is also lightly colored and reflects some of the incident light. Contains numerous stomata (However, is less than the number for normal plants - another water-saving characteristic.) 11. XEROPHYTES Possess many of the usual, water-conserving adaptations of such plants: A thick epidermis covered with wax Water-storage cells that cause the leaves to appear succulent (that is thick and fleshy Sheathing leaf bases. 12. Light DependentReactions Non-cyclic photophosphorylationCyclicphotophosphorylation 13. Light IndependentReaction:Calvin Cycle 14. HATCH SLACK PATHWAY Onlyoccurs inC4 plantsand CAMplants. 15. COMPARISON BETWEEN C3 , C4 , AND CAM PLANTS 16. EXAMPLES C3 plants C4 plantsCAM plants Tomato Sugarcane Cactus Legume Maize Bromeliad TobaccoSorghum WheatEleusine 17. CO2 FIXATION AND CO2 ACCEPTORC3 plants C4 plantsCAM plants Once, only inTwice, first in Once, only in mesophyll cells.mesophyll cells and then mesophyll cells. in bundle sheath cells.Ribulose Phosphoenelpyruvate Phosphoenelpyruv biphosphate RuBPPEP (3C) -mesophyllate PEP (3C) - (5C) mesophyll cells cellsmesophyll cells Ribulose biphosphate RuBP (5C) bundle sheath cells 18. ENZYME AND FIRST PRODUCT FORMEDC3 plants C4 plantsCAM plantsRuBP carboxylase PEP carboxylase PEP-inefficient at low CO2 -high affinity for CO2 low concentration -high affinity for CO2 at lowRuBP carboxylase concentration-efficient at highCO2 concentration. Glycerate 3- Oxaloacetate, a C4Oxaloacetate, aphosphate (GP), a C3 acid. C4 acid.acid. 19. PHOTORESPIRATION CO2+RuBP(5C) 2G3P (3C) O2+RuBP(5C) phosphoglycorate (2C)+G3P (3C) Phosphoglycorate was the react with O2 to form CO2 with no production of energy Is wasteful 20. PHOTORESPIRATION-O2 IS USED, CO2 IS RELEASED C3 plantsC4 plantsCAM plants Occurs. Inhibited by high Inhibited by high Oxygen acts asconcentration of CO2.concentration of competitive inhibitor. Light intensity & CO2.temperature arehigher, O2 is not acompetitive inhibitor. 21. EFFICIENCY OF PHOTOSYNTHESIS C3 plantsC4 plants CAM plants Less efficientPhotosynthesis Photosynthesis photosynthesis than C4 more efficient. more efficient. plant. Yields are usually Yields usually lower. much higher. 22. LEAF ANATOMY C3 plantsC4 plants CAM plants Two distinct tissues: Vascular bundleKrantz anatomy palisade cell surrounded by two absent mesophyll cellrings of cells: 1 type of Krantz anatomymesophyll cell chloroplast in absent bundle sheath cell mesophyll cells 1 type of chloroplast Thinner than C3 in mesophyll cells plant Vascular bundle packed tightly, many chloroplasts 23. CROSS-SECTIONS OF LEAVES FROM C3 AND C4 PLANTS. 24. THANK YOU..