Lecture01 - What is plant physiology What The science that...

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Unformatted text preview: What is plant physiology What The science that studies plant function How do plants obtain their nutrients? How do they convert solar energy to food? How do plants survive harsh environments? How do they respond to hormones and other stimuli? How do plant reproduce, protect, and nourish their offspring? How do plant fight to ward off disease-causing microorganisms? Major design elements of plants Major 1. Convert sunlight into chemical energy 2. Plants are non-motile but are capable of growing towards essential resources 3. Terrestrial plants are structurally reinforced to support their masses (by lignified secondary cell wall) 4. Terrestrial plants have evolved mechanisms to conserve water 5. Terrestrial plants are capable of moving water, minerals, & other essential nutrients The "Typical" Plant Body The The Shoot System Above ground (usually) photosynthesis reproduction & dispersal food and water conduction the shoot system includes leaves stems the reproductive organs: [flowers and fruits] The Root System Underground (usually) Anchor the plant in the soil Absorb water and nutrients Conduct water and nutrients Food Storage Unique features of plant cells Unique The secondary cell wall is made between the primary cell wall and between the cell membrane The Three Tissue Systems The (Parenchyma cell) The xylem tissue is a complex tissue comprising of vessel elements, tracheids, xylem parenchyma cells (transfer cells), and sclerenchyma cells tracheids The phloem is also a complex tissue containing sieve tube elements, The parenchyma cells (companion cells), and sclerenchyma cells parenchyma The organization of three different tissues in leaf The Plant Growth- growth is localized to specific areas called meristems, meristems which are the sites of repeated cell division of unspecialized cells These cells differentiate and become specialized in function Leaf primordium primordium Shoot apical meristem Shoot meristem Axillary meristem Apical Meristem gives rise to three primary meristems: Meristem meristems protoderm --epidermal tissue --epidermal ground meristem-->ground tissue ground meristem procambium-->vascular tissue Root Apical Meristem Root Meristem Most cell division is directed away from the root cap Quiescent Center Quiescent Populations of cells in apical meristem which reproduce much more slowly than other meristematic cells The Zone of Cell Division The (Primary Meristems) Meristems Protoderm - outermost primary meristem Protoderm meristem Ground meristem - central primary meristem meristem Procambium - innermost primary meristem meristem The Zone of Elongation Cells elongate up to ten times their original length, pushing the root further downward into the soil The Zone of Maturation The Region of the root where completely functional cells are found functional Root Cap (derived from the root apical meristem) Root meristem protects the delicate apical meristem protects secretes polysaccharide slime that lubricates the soil constantly sloughed off and replaced constantly Characteristic features of the meristematic cells 1. The cells are capable of undergoing regular, continuous mitotic divisions. 2. The cells are relatively smaller in size compared to mature cells. They are either rectangular or isodiametric in shape. 3. The cells are always compactly arranged, without any intercellular spaces. 4. The cells have a thin cell wall, which is composed of only cellulose. 5. The cells enclose a large amount of clear and transparent cytoplasm. 6. Every cell has a large nucleus, which is situated in the center of the cell. 7. The chromosomes are always found in some phase of mitotic division. 8. Except mitochondria, other cell organelles are either absent or present in a nonfunctional state. For example, the plastids may be present in a non-functional state called proplastids. 9. Vacuoles are either absent or very small. The formation of lateral roots The pericycle, jjust inside the endodermis, pericycle ust is a layer of cells that may become meristematic and divide to form the lateral root. A lateral root forms as a clump of cells in the pericycle, then elongates and pushes through pericycle then the cortex until it emerges from the primary root. the Lateral meristems add girth to stems and roots Lateral through secondary growth through 2nd growth results from two lateral meristems: meristems vascular cambium and cork cambium cork cambium Vascular cambium produces secondary xylem and phloem Cork cambium produces a tough, thick covering for roots and stems that replaces the epidermis. ...
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This note was uploaded on 11/30/2011 for the course BIOLOGY 321 taught by Professor Min during the Winter '11 term at University of Michigan.

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