Plant/Crop Physiology Plant physiology is a sub-discipline of botany concerned with the functioning of plants. Includes the study of all the internal activities of plants those chemical and physical processes associated with life as they occur in plants Crop Physiology Includes at the smallest scale : molecular interactions of photosynthesis and internal diffusion of water, minerals, and nutrients. at the largest scale : processes of plant development, seasonality, dormancy, and reproductive control. The scope of crop physiology as a discipline may be divided into several major areas of research. First The study of phytochemistry (plant chemistry) is included within the domain of plant physiology. In order to function and survive, plants produce a wide array of chemical compounds not found in other organisms. Photosynthesis requires a large array of pigments, enzymes, and other compounds to function. Because they cannot move, plants must also defend themselves chemically from herbivores, pathogens and competition from other plants. They do this by producing toxins and foul-tasting or smelling chemicals. Other compounds defend plants against disease, permit survival during drought, and prepare plants for dormancy. While other compounds are used to attract pollinators or herbivores to spread ripe seeds.
Secondly Plant physiology includes the study of biological and chemical processes of individual plant cells. Plant cells have a number of features that distinguish them from cells of animals, and which lead to major differences in the way that plant life behaves and responds differently from animal life. For example, plant cells have a cell wall which restricts the shape of plant cells and thereby limits the flexibility and mobility of plants. Plant cells also contain chlorophyll, a chemical compound that interacts with light in a way that enables plants to manufacture their own nutrients rather than consuming other living things as animals do. Thirdly Plant physiology deals with interactions between cells, tissues, and organs within a plant. Different cells and tissues are physically and chemically specialized to perform different functions. Roots and rhizoids function to anchor the plant and acquire minerals in the soil. Leaves function to catch light in order to manufacture nutrients. For both of these organs to remain living, the minerals acquired by the roots must be transported to the leaves and the nutrients manufactured in the leaves must be transported to the roots. Plants have developed a number of means by which this transport may occur, such as vascular tissue, and the functioning of the various modes of transport is studied by plant physiologists. Fourthly Plant physiologists study the ways that plants control or regulate internal functions. plants produce chemicals called hormones which are produced in one part of the plant to signal cells in another part of the plant to respond. Many flowering plants bloom at the appropriate time because of light-sensitive compounds that respond to the length of the night, a phenomenon known as photoperiodism. The ripening of fruit and loss of leaves in the winter are controlled in part by the production of the gas ethylene by the plant. Finally Plant physiology includes the study of how plants respond to conditions and variation in the environment, a field known as environmental physiology. Stress from water loss, changes in air chemistry, or crowding by other plants can lead to changes in the way a plant functions. These changes may be affected by genetic, chemical, and physical factors.
Cell Structures & Plant Anatomy Cells Types & Structural Differences Prokaryotic cells 1. No organelles 2. Cell membrane 3. Nucleiod 4. Cell wall 5. Ribosomes 6. Cytoplasm 7. Plasmid 8. Flagella/cilia NOT organelles Eukaryotic Cells 1. Organelles 2. Cell membrane 3. Cytoplasm 4. Ribosomes Animal cells 1. Lysosomes Plant Cells 1. Cell wall 2. Plastids 3. Large central vacuole Plant Cell Illustration The Cell Boundary Cell Wall - structure found around plant cells, fungi cells, and certain protists, as well as prokaryotic cells. Located outside of the plasma membrane and is composed primarily of cellulose (in plants).
Plant cell walls Extracellular cell wall made of cellulose. Plasmodesmata connect neighboring cells Primary cell walls--all plant cells Secondary cell walls only in some cells Lignin--polymer of alcohols, stable, resistant waterproof coating The Cell Boundary Plasma Membrane - selectively permeable membrane that is approximately 0.1 um thick
Internal Structures of Cells Cytoplasm - semi fluid, that serves as a pool of raw materials. Most (70%) is water, and the rest is proteins (mostly), carbohydrates, and nucleotides, as well as their monomers. Nucleus Two chief functions a) carry hereditary information b) exert influence on ongoing cell activity, helping to to maintain homeostasis. Contains DNA in the form of chromatin fibers or chromosomes Nuclear Envelope - double membrane formed by two lipid bi-layers perforated by pores through which RNA passes Nucleolus (typically 2 per cell) - it manufactures ribosomal RNA Organelles of Synthesis, Storage, and Export Endoplasmic reticulum Network of flattened hollow tubules and channels Smooth ER - manufactures lipids, contains enzymes that detoxify certain poisons, transports carbohydrates, lipids, and other non-proteins. Rough ER - these tubules are studded with ribosomes Ribosomes small structures occurring mostly in the cytoplasm site of protein synthesis molecular complexes of ribosomal RNA and proteins.
Golgi Apparatus Collection of flat sacs that transport proteins produced by rough ER to the outside of the cell. Enzymes in the Golgi apparatus modify proteins by adding functional groups. Microbodies Peroxisomes - aid in the metabolism of glycolic acid during cell respiration Glyoxysomes - contain enzymes aiding conversion of fats to carbohydrates during seed germination of some plants. Energy Organelles 1. Mitochondria - double membrane bound organelle ATP is produced here by cell respiration elongate and surrounded by 2 phosphobilipid membranes
Energy Organelles 2. Plastids - found in plants, some protists a. Chloroplasts - site photosynthesis contain chlorophyll pigment double membranes like mitochondria b. Chromoplasts - store yellow, orange, and red pigments give the color to fruits and flowers Electron micrograph of a chloroplast from a leaf of timothy grass, Phleum pratense c. Leucoplasts - store starches and proteins in plants Vacuoles - Small in animal cells (storage) Plant cells - Central Vacuole appears as empty space, pushing the other organelles and cytoplasm towards the outer boundary of the cell & storing water. Vacuoles bound by a single membrane - tonoplast. Functions: a) taking up space; pushing other organelles closer to the plasma membrane & give cell its shape, b) store waste products to be released later or to prevent other organisms from eating them c) in some single-celled organisms, they are used to eliminate water (Contractile Vacuole).
The cells of a plant are classified into three cell types Parenchyma cells Collenchyma cells Sclerenchyma cells Parenchyma cells Least specialized cell type Primarily involved in metabolism Thin primary cell wall (no secondary cell wall) Alive at maturity Examples: photosynthetic cells of the shoot system, starch- or sugar-storing cells Collenchyma cells Unevenly thickened primary (1 ) cell walls Mechanical support Cell walls are flexible (no 2 cell walls) Alive at maturity Example: the 'strings' in a stalk of celery Sclerenchyma Mechanical support Thick secondary cell walls, often with lignin Usually dead at maturity Fibers-long, sclereids-short Examples: flax stems (fibers), walnut shells, gritty cells in pears (sclereids), xylem cells
The cells of a plant are organized into three tissue systems Dermal Vascular Ground Dermal tissue system Function: protection, minimize water loss Epidermis covered by a waxy cuticle Leaves -- stomata and guard cells - by which air enters the leaf. Long root hairs increase surface area for water absorption. Vascular tissue system-xylem Transport of water (and all dissolved solutes) from roots Tracheids and vessel elements conduct water Thick 2 cell walls Dead at maturity Tracheids and vessel elements Tracheids: narrow and elongated Pits Gymnosperms have only tracheids Vessel elements - short and cylindrical Line up end-to-end (vessel) Holes in their end walls allow free movement of water Only in angiosperms
Vascular tissue system-phloem Sieve-tube members, companion cells Alive at maturity Sieve-tube members lack nuclei and ribosomes. Dependent on companion cells Active transport between the cytoplasm of successive sieve-tube members via plasmodesmata. Selectively transport specific solute molecules (e.g. sucrose). Vascular tissues also provides some mechanical support From the cell walls of tracheids and vessel elements (sclerenchyma) From the hydrostatic pressure of the liquids within the vascular tissue Ground tissue system Fills the spaces between the epidermis and vascular tissues