Plant Cellular Processes

Topics: Leaf, Plant physiology, Phloem Pages: 9 (2842 words) Published: March 2, 2013
evolved morphological, anatomical and physiological adaptations to obtain, process, transport and store raw materials and energy under varying conditions. capture and conversion of radiant energy to chemical energy takes place in chloroplasts (chloroplasts are localized in specialized tissues) products of photosynthesis are used in respiration, growth, repair, maintenance, storage. energy consuming reactions must take place for the substances of photosynthesis to be transported around the plant. energy is supplied to plant cells through respiration

movement of substances occurs by diffusion, osmosis and active transport. Water and mineral ions must be supplied and conserved in the plant. cell wall makes plants have no mobility
cell wall bring turgor pressure. Turgor pressure increased in ‘woody plants’ - with lignin. photosynthesis - is the process whereby radiant energy from the sun is converted to the chemical bond energy of glucose. It occurs in chloroplasts within specialised cells. chlorophyll- convert light energy to the chemical bond energy of ATP energy to transform carbon dioxide and hydrogen (from water) to glucose is provided by this ATP oxygen is given off as a waste product

carbon dioxide + water ➞ glucose + oxygen
6CO2 + 6H2O ➞ C6H12O6 + 6O2
broad flat part - the lamina
petiole/stem - joins the lamina to the plant
xylem - running through the petiole - transport water and mineral ions from the roots phloem - transporting sugars and other small organic molecules to different parts of the plant. epidermis - function is to protect the inner layers of cells - is a close fitting layer on both the top and bottom of the leaf. epidermal cells sometimes secrete a waxy cuticle - reduces evaporation from cells. lower epidermis there are stomata

each stoma is surrounded by guard cells - can open/close the space between them. guard cells contain chloroplasts / epidermal cells do not contain chloroplasts

water loss is reduced by having stomata underneath the leaf
upper leaf surface receives most light energy - but it is exposed to higher air movements and temperatures - these increase evaporation rate.

carbon dioxide needed for photosynthesis passes through the stomata along a diffusion gradient from the air to the cells. concentration of CO2 inside inner mesophyll cells will be lower than that in the atmosphere. oxygen is released as a product - passes out of the stomata along a diffusion gradient.

mesophyll cells [1 palisade layer, 2 spongy mesophyll layer] contain chloroplasts air spaces are in the spongy mesophyll layer
mesophyll contain veins which carry vascular tissue

Supported by stem and petioleexposes as much sunlight and air as possible onto the leaf Large surface areaexposes as much of the leaf as possible to retain sunlight to be used for photosynthesis stomata on lower epidermisallows CO2 and O2 to diffuse in and out; to reduce evaporative water loss air spaces in spongy mesophyll allows H20 C02 and 02 to diffuse to and from all cells. no chloroplasts in epidermisallows sunlight to penetrate into mesophyll layers cytoplasmic streamingmaintains chloroplasts in position to receive maximum light leaf arrangement on stemmaximizes light absorption

cytoplasmic streaming - the flow of cytoplasm around the cell. materials diffusing into 1 end of a sieve cell are picked up by the streaming cytoplasm and carried to the other end of the cell, where they diffuse across the sieve plates (may involve active transport) and are picked up by the streaming cytoplasm of the next element. this explains opposite movements of solutes in a tube

the release of chemical bond energy generally involves oxidation of sugar in a series of small steps each controlled by an enzyme energy is stored in ATP bond - is transported to other areas of the plant or is used by the cell cell cytoplasm - if oxygen is not present,...
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