nutrition & transport in flowering plant

• label the internal structure of leaf: 1) cuticle 2) epidermal cell 3) palisade mesophyll cells 4) spongy mesophyll cells 5) intercellular air spaces 6) stoma 7) guard cell 8) phloem 9) xylem

  
• what is the SF upper epidermis: structure— single layer of closely packed cells (epidermal cells) covered by a waxy & transparent cuticle on the outside. function— waterproof to reduce water loss through evaporation. transparent to allow light to enter the leaf
• what is the SF of palisade mesophyll: structure— one or two layers of closely packed long, cylindrical cells containing numerous chloroplasts. function— chlorophyll in chloroplast traps light & converts light energy to chemical energy by photosynthesis. more light is trapped on the surface of leaf, hence has most chloroplasts.
• what is the SF of spongy mesophyll: S1— irregular shaped cells with intercellular air spaces. F1— rapid diffusion of CO2 & O2 into & out of mesophyll cells. S2— chloroplasts less than palisade mesophyll layer. F2— more light trapped on surface of leaf. S3— cells covered by thin film of moisture. F3— allow CO2 to dissolve & diffuse into cells. S4— contains vascular bundle. F4— transports H2O & mineral salts to cells, manufactured food away from cells.
• what is the SF of lower epidermis: structure— single layer of closely packed cells covered by a waxy cuticle. function— reduces water loss through evaporation
• what is the SF of stomata: function— pores on the epidermis regulated by guard cells. function— opens in the presence of light allowing CO2 to diffuse in and O2 to diffuse out for photosynthesis, guard cells can photosynthesise (contains chloroplasts)
• label the cross-section of a plant stem: 1) epidermis 2) phloem 3) xylem 4) pith 5) cambium

  
• what is the SF of xylem vessel: S1— dead empty vessel with lumen without protoplasm & cross-walls. F1— conducts water & dissolved mineral salts from roots to stems & leaves rapidly as resistance to water flow is reduced. S2— inner walls lined with lignin— provide mechanical support for plant
• what is the SF of sieve tubes in phloem vessel: structure— consists of elongated, thin-walled living sieve tube cells, cross walls present, cytoplasm of sieve tube cells are interconnected. function— holes in sieve tube allow rapid transport of sucrose (produced as glucose during p/s) & amino acids from the source to the sink
• what is the SF of companion cells in phloem vessels: structure— metabolic processes & contains many mitochondria, cytoplasm & nucleus. function— provides energy to load sugars from mesophyll cells into sieve tubes by active transport
• what is the SF of root hair cell: S1— long & narrow protrusion. F1— increases SA:vol of cell to increase rate of absorption of water & mineral salts. S2— presence of large numbers of mitochondria. F2— releases energy during aerobic respiration to absorb mineral salts by active transport
• what is photosynthesis: chlorophyll absorbs light energy & converts it into chemical energy. the chemical energy is used to synthesise carbohydrates from water & CO2. water & CO2 are the raw materials for photosynthesis. O2 is released during the process.
• importance of photosynthesis: availability of chemical energy from light energy, removal of CO2 and production of O2, stored as energy as fossil fuels
• importance of glucose (RWS SAF): cellular respiration to release energy for cellular activities, formation of cell walls, converted to starch for storage (use during absence of light)
• describe the process of how CO2 reaches the mesophyll cells: CO2 enters through stomata. CO2 used up within leaf during photosynthesis. concentration of CO2 decreases and is lower than atmospheric CO2 concentration. atmospheric air‘s concentration is higher, CO2 diffuses in through stomata into air spaces in leaf. CO2 dissolves in the moisture layer in spongy mesophyll cells & dissolved CO2 diffuses into cells.
• what is transpiration: loss of water vapour from aerial parts of a plant, especially through the stomata of the leaves
• describe the process of the entry of water into plant: epidermal cells bear a fine tubular outgrowth which grows in btw soil particles, in contact with soil solution. thin film of liquid surrounding soil particles is a diluted solution of mineral salts. cell sap of root hair cell has lower potential than soil solution. water molecules enter root hair cell by osmosis through the partially permeable membrane. entry of water dilutes cell sal & root hair cell has higher water potential than surrounding cell. water molecules passes by osmosis from root hair cell into inner cell.
• how does wilting occur: transpiration rate exceeds rate of water absorption by roots, mesophyll cells lose turgor due to water molecules moving out of cell sap, cell becomes flaccid & wilt
• what is translocation: transport of manufactured food substances such as sugars and amino acids in plants with the expenditure of energy