Nutrition in Plants (5078 syllabus)

Nutr ition in Plant s 1 Nutrition in Plants External: 1. Lamina large and flat: Obtain max amt of light thin: CO2 can reach inner cells at faster rate 2. Veins (mid-rib and branch vein) Carry water and mineral salts to leaves manufactured food to other parts of plant 3. Petiole Hold leaf away from stem obtain sunlight and air Internal: Upper Epidermis Single layer of cells no chloroplasts Covered by waxy cuticle which: Protect leaf tissue Prevent excessive evaporation of water Mesophyll Mesophyll (two kinds: Palisade mesophyll and Spongy mesophyll) Main site for photosynthesis

Nutr ition in Plant s 2 Palisade mesophyll 1-2 layers closely packed, elongated cells has most chloroplasts → enable them to absorb maximum sunlight for photosynthesis Spongy mesophyll cells are irregularly shaped less chloroplasts Contain numerous large intercellular air spaces rapid diffusion of gases thru leaf Covered in thin film of moisture so that co2 can dissolve in it phloem and xylem found Lower Epidermis

Nutr ition in Plant s 3 same as upper but, with guard cells and stomata guard cells: control size of stomata Stomata: allow for gaseous exchange Stomata: OPEN: open in day and close in night guard cells got chloroplasts photosynthesis in day become concentrated inside WP (water potential) decrease water enter guard cells cell become turgid and bean-shaped stoma open CLOSE: carbohydrate made during the day diffuses out of leaf WP increase water leave guard cells guard cells become flaccid stoma close

Nutr ition in Plant s 4 Photosynthesis: Define: light energy absorbed by chlorophyll converted into chemical energy energy used to synthesize glucose from water and co2 o2 gas released in process Carbon dioxide + Water → Glucose + Oxygen + Water (arrow consist of sunlight and chlorophyll) photo(light) synthesis(put tgt) What happens to the glucose produced from photosynthesis? broken down by cells during cellular respiration to provide energy for cellular activities make cellulose cell walls form fats react with nitrate → form amino acids converted into sucrose → translocated away converted to starch during the day starch converted back to glucose Limiting Factors Define: ANY factor that directly affect process if quantity is changed Factors of photosynthesis? 1. Light Intensity 2. Carbon dioxide concentration 3. Temperature

Nutr ition in Plant s 5 At X: as light Intensity increase, rate of photosynthesis increase At Y: rate of photosynthesis remains constant. Light Intensity no longer limiting factor, could be either temperature or carbon dioxide conc How to increase rate of photosynthesis: increase co2 conc or temperature till optimum