Leaf structure Mineral requirements

Cross section of a leaf Xylem/ Phloem Stomata 2 guard cells control the opening and closing of stomat

Function of leaf parts (Review) Structure Function Epidermis Top thin layer (protective). Prevents water loss and over heating of leaf Cuticle Waxy layer of the epidermis- Prevents water loss and over heating of leaf Spongy Mesophyll / Palisade cells Photosynthesis – there are more chloroplast in the palisade cells than the mesophyll cells are- this is where the majority of photosynthesis happens. Palisades are long – to maximize surface area. Spongy cells are round and few – allows for air to travel to the palisade cells (gas exchange) stomata Allows air to come in and out of leaf ( gas exchange) Guard cells Control the opening and closing of stomata Vascular bundle Has the xylem and phloem running through the leaf xylem Transports water into the leaf / structural support phloem Takes substance away (sugar) that the leaf has made to other pars of the cell / structurally support

Mineral Requirements Plants can use the carbohydrates they make to make protein. Proteins – C/H/O/ & N (Nitorgen) Plants get their nitrogen from inorganic compounds like nitrate ions and ammonia ions. Even though 80% of air is nitrogen oxide – it is mostly useless to plants as it is unreactive Nitrates (NO3- / NH4+) taken up by roots If not enough nitrates – can’t make protein / can’t make new cells The plant will have stunt (short) growth / weak

Nitrates are needed to make enzymes for the plants Smaller / less green / less healthy Farmers can supplement this by adding nitrates to the soil in form of fertilizer Magnesium ions: Needed to make green pigment in chlorophyll Plant leaves become yellow if magnesium not there quickly Efficiency of photosynthesis goes down