12.2 Flashcards
how does carbon dioxide enter the leaf
carbon dioxide diffuse frm surrounding atmospheric air through stomata into intercellular air spaces in leaf, carbon dioxide gas dissolves in thin film of water surrounding mesophyll cells, dissolved carbon dioxide diffuses into mesophyll cells
how does water enter the leaf
xylem transport water and mineral salts from roots to leaf, water molecules move by osmosis from xylem vessel into surrounding mesophyll cells
adaptations of xylem (3 points)
long hollow continuous tube from roots through stem to leaves, empty lumen without cytoplasm and cross walls, inner walls of xylem vessels are deposited with lignin (hard and rigid substance)
function of long hollow continuous tube (xylem)
rapid transport of water and dissolved mineral salts from roots to all parts of plant
function of empty lumen without cytoplasm and cross walls
reduce resistance to water flowing through xylem
why are inner walls of xylem vessels deposited with lignin
lignin prevents collapse of individual xylem vessels, together, all xylem vessels provide mechanical support to plant
what are the two parts of phloem
sieve tube and companion cells
what are sieve tubes
elongated thin walled living cells with only a thin layer of cytoplasm inside the cell (lost its central vacuole, nucleus, most organelles) to allow rapid flow of sucrose and amino acids through the sieve tubes
what are companion cells
marrow thin walled cells with many mitochondria, cytoplasm and nucleus to provide glucose and oxygen to sieve tube cells to load sucrose and amino acids from mesophyll cells into sieve tubes by active transport
why do companion cells have numerous mitochondria
release energy for active transport for loading of sucrose from the mesophyll cells into sieve tubes, release energy needed for metabolic activities of sieve tube cells
what is role of chlorophyll
absorb light energy, convert light energy into chemical energy, stored in glucose during photosynthesis
what is purpose of a control set up
to show that any result observed is a result of varying changed variables
