Mrs Ragsdale Biology HL

 Ground tissue ◦ Basic survival functions for plant, such as gathering of water and nutrients ◦ Storage  Vascular tissue (think arteries and veins) ◦ Distribution of water and dissolved nutrients  Dermal tissue (think plant skin) ◦ Protection and covering of plants

 Parenchyma ◦ Pliable, soft, thin-walled cells that make up the tissue where primary growth takes place ◦ Site of gas exchange in leaves ◦ Used for storage and secretion  Collenchyma ◦ Support cells that are typically long and flexible ◦ Appear primarily in lengthening stems and stalk ribs  Sclerenchyma ◦ Thick, stiff walls that are made stronger by adding lignin ◦ Waterproofs the cell ◦ Adds protection  Fibers or sclerids

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 Vascular – Transport system ◦ Xylem – Transports from the roots to the stems  Also offers mechanical support ◦ Phloem – Transports from the stems to the roots  Dermal – Outer protection (skin) ◦ Epidermis – covers surfaces of the plant ◦ Cuticle – thick waxy covering ◦ Stoma (Stomata plural) – “pores” or the openings along the epidermis for gas exchange

 Connect leaves roots and flowers  Vital role in transport – location of xylem and phloem  Support aerial portion of plant ◦ Cell turgor – cells absorb water until they are under high pressure. This high pressure helps give support by making the cells rigid ◦ Cell walls in xylem have lignin in them making them extremely strong  In woody stems, xylem especially gives support

 Plant’s version of “stem cells”  Meristem tissue is always going to be the site of plant growth and cell differentiation  Apical meristem – located at the tips of stems and roots  Lateral meristem – dicotyledonous plants are able to grow outwards as well as upwards. The lateral meristem develops between xylem and phloem and allows this outwards growth.

Apical meristem Dicotyledonous Plant Dicot Stem Cross Section

 Site of photosynthesis ◦ Leaf structure related to function – designed to maximize exposure to sun ◦ Location of chloroplasts  Site of transpiration ◦ Designed to protect from losing too much water during the heat of the day

 Leaf blade (lamina) – main part of the leaf, designed to absorb sunlight  Palisade mesophyll – densely packed cylindrical cells with a large amount of chloroplasts  Spongy mesophyll – loosely packed rounded cells with few chloroplasts, main site of gas exchange in the tissue  Stoma – pores that open and close, site of gas exchange  Guard cells – the “muscular” cells that open and close the stomata  Upper epidermis – continuous layer of cells covered by a thick waxy cuticle

 Basic job of roots is to absorb water and minerals from soil  Roots increase surface area by branching off and growing root hairs  Concentration of minerals is typically greater in the root than in the soil so active transport methods are used ◦ This takes ATP! ◦ Roots typically have mitochondria to assist with active transport

1. Diffusion of mineral ions 2. Fungal hyphae (mutualism) ◦ Fungus grows near the roots of the plant ◦ Mutualistic relationship because both fungus and plant benefit 3. Mass flow of water in the soil carrying ions when water drains through the soil

 No plasma membranes so water is free to move  Cells are “dead” at maturity and hollow  Sieve tubes allow water to move out of the xylem vessel and into the cell walls of leaves  Xylem moves water and dissolved minerals up from the roots to the leaves

 How does xylem manage to pull water up its empty tubes? ◦ Continuous flow of water during transpiration – transpiration stream ◦ Transpiration pull – low pressure suction inside the xylem vessel caused by capillary action ◦ Cohesion – water molecules tend to pull tightly together because of hydrogen bonding ◦ Adhesion – water sticks to the walls of the xylem because of its adhesive nature

 Phloem flows from the leaves (the site of photosynthesis aka the candy shop) down to the roots  Active transport of sugars and amino acids  The places where sugars are made are called sources and taken down to the roots also called sinks

Monocotyledon – one baby seed leaf Dicotyledonous – two baby seed leaves  Leaf veins run parallel to each other  Vascular bundles spread randomly in the stem  Stamens, flowers and other organs are in multiples of 3  Unbranched roots grow from stems  Leaf veins form net- like patterns  Vascular bundles in a ring near the outside of the stem  Stamens, organs and flowers in multiples of 4 or 5  Roots branch off from other roots

 Bulbs – underground organs that are made from leaf bases ◦ Used for food storage ◦ Monocotyledon plants ◦ Serioes of leaf bases fitting inside each other with a central shoot apical meristem

 Storage Roots ◦ Some roots swell up with stored food ◦ Typically have vascular tissue in the centre

 Stem tubers ◦ Dicotyledon plants ◦ Plant stems grow downward into the soil ◦ Sections then grow into stem tubers which are used for food storage ◦ Identified as stems because their vascular bundles are in a ring

 Tendrils ◦ Narrow outgrowths from leaves that create a corkscrew ◦ Once they touch a support, they attach to it ◦ Used by the plant to grow upwards

 Transpiration MUST be controlled or plants will lose too much water  Abscisic acid – release causes guard cells to close which then close the stomata  Plants produce abscisic acid when they are dealing with water stress

 Light – typically stomata open during light and close at night  Temperature – heat needed to make water evaporate ◦ High temperatures = higher rates of transpiration ◦ Lower temperatures = lower rates of transpiration  Humidity – lower humidity leads to higher rates of transpiration  Wind – higher wind increases transpiration rates

 Plants adapted to dry habitats  CAM plants – stomata open during the night and not the day ◦ Light dependant reactions occur during they day ◦ Light independent reaction occurs at night  Stems tend to be vertical to absorb early sunlight  Spines instead of leaves to reduce surface area  Thick waxy cuticles to keep water in ques/houseplants_cactus1.shtml

 Reduced leaves into spines  Thick waxy cuticles  Reduced number of stomata  Deep root systems  Water storage tissue  CAM physiology – adaptation to photosynthesis