Plant tissues, organs and systems

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  • The Secret Life of Plants - Plant tissues, organs and systems
    • PLANT CELLS are organised into TISSUES and ORGANS
      • PLANTS are made of ORGANS like STEMS, ROOTS and LEAVES, they work together to make ORGAN SYSTEMS.
        • They perform the tasks the plant needs to survive e.g. TRANSPORTING SUBSTANCES around the plant
        • Plant organs are made of TISSUES
          • EPIDERMAL TISSUE - COVERS whole plant.
          • PALISADE MESOPHYLL TISSUE - Most PHOTOSYNTHESIS happens
          • SPONGEY MESOPHYLL TISSUE - Contains big AIR SPACES to allow GASES to DIFFUSE in and out of cells.
          • XYLEM and PHLOEM - TRANSPORT things like WATER, MINERAL IONS, and FOOD around the plant
          • MERISTEM TISSSUE - Found at GROWING TIPS of SHOOTS and ROOTS and able to DIFFERENTIATE into lots of DIFFERENT TYPES of plant cell, allowing it to GROW.
    • The LEAF is an ORGAN made up of SEVERAL TYPES OF TISSUE
      • Leaves contain EPIDERMAL, MESOPHYLL, XYLEM and PHLOEM tissues.
        • Epidermal tissues - covered with a WAXY CUTICLE which helps REDUCE WATER LOSS by evaporation
          • UPPER EPIDERMIS - TRANSPARENT so light can pass through to the PALISADE LAYER
          • The TISSUES of leaves are also adapted for efficient GAS EXCHANGE. The LOWER EPIDERMIS is full of different holes called STOMATA, which lets carbon dioxide diffuse directly into the leaf.
            • The opening and closing of stomata is controlled by GUARD CELLS in response to environmental conditions.
              • GUARD CELLS are adapted to OPEN AND CLOSE STOMATA
                • Have kidney shape which OPENS and CLOSES the STOMATA in a leaf.
                  • LOTS of water = they fill up and goes TURGID. Makes it OPEN so GASES can be exchanged for PHOTOSYNTHESIS
                  • SHORT on water=they lose water and become FLACCID, making them CLOSE. Helps stop too much water vapour ESCAPING.
                  • Adaption: THIN outer walls and THICKENED inner walls make it work
                  • SENSITIVE TO LIGHT and CLOSE AT NIGHT to save water without losing out on photosynthesis.
        • Mesophyll
          • PALISADE LAYER - Lots of CHLOROPLASTS. Meaning they're near the top of the leaf where they can get the most LIGHT.
          • The AIR SPACES in the SPONGEY MESOPHYLL tissue INCREASE the rate of diffusion of gases.
        • XYLEM and PHLOEM form VASCULAR BUNDLES, they DELIVER WATER and other NUTRIENTS to the entire leaf and take away the GLUCOSE produced by photosynthesis, also help SUPPORT the structure.
    • TRANSPIRATION AND TRANSLOCATION
      • PHLOEM TUBES transport FOOD
        • XYLEM and PHLOEM - TRANSPORT things like WATER, MINERAL IONS, and FOOD around the plant
        • XYLEM and PHLOEM form VASCULAR BUNDLES, they DELIVER WATER and other NUTRIENTS to the entire leaf and take away the GLUCOSE produced by photosynthesis, also help SUPPORT the structure.
        • Made of: columns of ELONGATED living cells with small PORES INT HE END WALLS to allow CELL SAP to flow through
          • Transport FOOD SUBSTANCES, mainly dissolved SUGARS made in leaves for IMMEDIATE USE or STORAGE
            • Transport goes BOTH DIRECTIONS
              • Process is called TRANSLOCATION
      • XYLEM TUBES take water UP
        • Made of: DEAD CELLS joined end to end with NO en walls between them and a hole down the middle. Strengthened with LIGNIN
          • Carry WATER and MINERAL ions from the ROOTS to the STEM and LEAVES.
            • Movement of water FROM the ROOTS, THROUGH the XYLEM and OUT of the LEAVES is called the TRANSPIRATION STREAM
      • TRANSPIRATION is the LOSS OF WATER from the plant
        • Movement of water FROM the ROOTS, THROUGH the XYLEM and OUT of the LEAVES is called the TRANSPIRATION STREAM
        • Caused by the EVAPORATION and DIFFUSION of water from a plant's surface. Mostly happens at LEAVES.
          • Evap causes slight SHORTAGE of water in leaf so more is drawn up from the rest of the plant through the XYLEM VESSELS to replace it.
            • Means more water is drawn up from ROOTS (hairs give large surface area) and so a constant TRANSPIRATION STREAM of water through the plant.
          • It is a SIDE-EFFECT of the way leaves are adapted for PHOTOSYNTHESIS. They have to have STOMATA in them so that gases can be exchanged easily.
    • TRANSPIRATION RATE FACTORS
      • LIGHT INTENSITY - BRIGHTER=GREATER rate. STOMATA CLOSE as it gets darker, photosyntheis can't happen in dark, so they don't need to be open to let carbon D in. When closed little water can escape.
      • TEMPERATURE - WARMER=FASTER. When warm water particles have MORE ENERGY to diffuse and evaporate out stomata.
      • AIR FLOW - BETTER AF=GREATER RATE. If poor, water vapour just SURROUNDS THE LEAF and doesn't move away. Means high conc in and out so DIFFUSION doesn't happen quickly. If good WV is SWEPT AWAY, maintaining low conc outside.
      • HUMIDITY - DRIER air=FASTER rate. Same as air flow.
      • MEASURING RATE OF TRANSPIRATION
        • Estimate by measuring UPTAKE of water by a plant. Because you can assume that WATER UPTAKE by plant is related to WATER LOSS by the leaves.

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