PLANTS – DAY 1 INTRODUCTION TO PLANTS

WHAT ARE PLANTS?  Plants provide nourishment for all organisms  With the help of protists and fungi, plants provide oxygen we breathe and food that sustains us – directly or indirectly, by feeding other animals  Plants provide shade over our heads and cool carpets under our feet while surrounding us with beautiful colours and marking the changing of the seasons  Prominent plants give us a handle on ecological communities – descriptions such as ‘redwood Tanoak Forest indicate the plants we will find there but also the animals, fungi, and climate of the area, too

PHOTOSYNTHESIS  The process by which plants (autotrophs)use chlorophyll to trap sunlight energy and use it to produce carbohydrates  Chlorophyll: is a green pigment in plants that absorbs sunlight and is the site of oxygen production in plants  The bonds in carbohydrates store chemical energy  6 CO H 2 O C 6 H 12 O 6 + 6O 2 sunlight  Photosynthesis occurs only during the day and only to depths where sunlight can penetrate

PHOTOSYNTHESIS

PHYLOGENY OF PLANTS  Early green algae eventually gave rise to nonvascular plants (Bryophytes) such as mosses and liverworts and vascular plants (Gymnosperms, Angiosperms)  Nonvascular plants: have no conductive tissues found in vascular plants. These plants are unable to pull up water and up from the ground to any significant distance. These plants do not flower; they reproduce via spores.  Vascular plants: describes the system of supportive and conductive tissue found in plants to transport water and dissolved materials throughout a plant. This makes up the vascular system, which is the equivalent of a human circulatory system.

PHYLOGENY OF PLANTS

WE EXAMINE VASCULAR PLANTS Cells in all multicellular organisms, plants being no different, are organized into tissues, tissue systems, organs and organ systems and these structures enable plants to successfully photosynthesize, grow and reproduce

MERISTEMS  Plant cells divide by mitosis only in specific regions called meristems  Cells produced by meristematic tissue eventually differentiate into all other plant tissues, that are arranged into specialized organs called roots, stems, leaves, cones or flowers  Apical Meristems: located at the tips of roots and shoots and supply cells for the plant to increase in length (grow up for shoots and down for roots) – growth in this direction known as primary growth  Lateral Meristems: located near the periphery of the plant; usually in the vascular tissue. Supply cells for the plant to increase in girth (width) – growth in this direction is known as secondary growth

PLANT TISSUE  Plant tissues are specialized for functions like absorption, transport, storage, photosynthesis and reproduction  3 major types of plant tissue: DERMAL, GROUND AND VASCULAR

PLANT TISSUE - DERMAL  Dermal Tissue –  outermost cell layer of the main plant body is epidermis  on parts of the shoot system, epidermis produces on its exterior surface a waxy, noncellular layer called the cuticle. Cuticle protects against excessive water loss and infection by microorganisms  epidermal tissue has highly specialized cells called root hair cells and leaf guard cells

PLANT TISSUE - GROUND  Ground Tissue –  -are 3 types of ground tissues: parenchyma, collenchymas and sclerenchyma  Parenchyma living cells that make up bulk of plant body; involved in photosynthesis and storage of nutrients, carbohydrates and water  Collenchyma – Living cells that helps to strengthen the plant and is specialized for supporting the plant’s primary growth areas; have thickened cell walls that allow for flexibility to plant parts that must be able to bend to withstand windy conditions  Sclerenchyma – cells that have 2 cell walls! Composed of cellulose and lignin, a material that provides added strength and rigidity to the cell; allows extra strength and support to various plant parts – these cells can be found almost anywhere a plant needs them

PLANT TISSUE - VASCULAR  Vascular Tissue – includes xylem and phloem and some collenchymas and parenchyma cells  Roots hold the plant steady and grab moisture and nutrients from the soil. The top is in the light, conducting photosynthesis and helping the plant reproduce. You have to connect the 2 parts – where xylem and phloem come in!  XYLEM  The system of tubes and transport cells that circulates water and dissolved minerals  Plants have roots to help absorb water – to get water to rest of the plant, xylem is required to function  Xylem is made of vessels that connect the plant from end to end, for maximum speed to move water and minerals around  Xylem tissue dies after about one year, all that remains are the cell walls  These dead cells continue to transport water and dissolved minerals until they get filled with various deposits

PLANT TISSUE – VASCULAR  PHLOEM  Most plants have green leaves where photosynthesis occurs  When food (glucose/carbohydrates) are made, it needs to get to every cell in the plant – this is where phloem comes in!  Phloem cells are laid out end to end throughout the entire plant, transporting the glucose created by the plant  PHLOEM IS ALWAYS ALIVE. Mature phloem is a living tissue!  sieve tubes provide a pathway for the movement of materials from one cell to the next; sieve tubes are made of sieve elements, which are long and thin phloem cells with sieve plates at the end walls  sieve elements associated with companion cells that direct the activities of the sieve tubes and supply them with needed substances 