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Mary Lou Wood BIOL490 – Senior Seminar Dr. P. Smith Spring 2010 What Are Vascular Plants? ◦ Characteristics ◦ Plant Nutrition Macronutrients and Micronutrients The Nitrogen Cycle ◦ Structure and Function Roots Stems Leaves Movement of Water and Minerals in Xylem Movement of Food Through the Phloem Divisions Macronutrients – mineral elements (inorganic elements) that are required in relatively large amounts. Micronutrients – minerals found in relatively smaller amounts N2 N2 N2 NH4+ NO2NO3- Mycorrhizae – mutualistic associations of fungi and plant roots in the soil that facilitate in the uptake of nutrients by the roots. Increase biomass due to better use of nutrients and water Improved resistance to stress conditions (biotic and abiotic) Protective effect against contaminants - heavy metals and other pollutants - by blocking them before absorbed by the plant Protective effect against root diseases (soil pathogens) and nematodes The principal functions of roots are to: ◦Anchor the plant in the soil ◦Absorb nutrients and moisture ◦Can serve as food storage organs ◦Provide a means of propagation Course textured sandy soils with large pores can hold the least amounts of available plant water. Fine textured soils with small pores can hold the greatest amounts of available plant water. Adventitious roots Taproots Passage cells The principal function of stems are to: ◦Form the framework that supports leaves, buds, flowers and fruit ◦Be a major part of the plant's transport system ◦Serve as food storage organs (asparagus) ◦Provide a means of propagation Annuals ◦Completes entire life cycle in a single growing season Biennials ◦Takes 2 years to complete life cycle Perennials ◦Lives for more than 2 years Lenticels on bark a. dicot stem b. monocot stem stolon tubers bulb tendrils stem leaves corm Cladode – a flattened stem resembling and functioning as a leaf. Leaves are reduced to spines to prevent water loss in transpiration. The stem is enlarged for the storage of water. The stem carries out photosynthesis. Thin, flattened structures that amplify the photosynthetic capacity of plant Come in variety of shape/size Parallel venation Netted venation Vascular tissues ◦Vascular tissues make up the water/food conducting system of a plant. They consist of the xylem and phloem. Xylem The xylem tubes are the water/mineral conducting channels and are made up of cells that are shaped into columns that can effectively move water through even the largest tree. Phloem Phloem tubes move food produced by photosynthesis to other parts of the plant. Water moves into the root by osmosis, and then into xylem Water forms a cohesive column in root/stem xylem Tension pulls the water column up and out in the xylem of veins in the leaves Water evaporates from mesophyll cells Water vapor diffuses out of stomates Psilophyta ◦No differentiation of cells into true roots and leaves and has simple kind of conducting system ◦Whisk ferns Lycophyta ◦Club mosses, with cells differentiated into roots, stems, and leaves Sphenophyta ◦horsetails Ferns, 12,000+ species Flattened leaves – broad expanse of photosynthetic surface Extensively branched Produce seeds Posses a cambium layer, meristematic Make up the bulk of the botanical world today Gymnosperm – naked seed Angiosperm – enclosed seed Fried, George and Hademos, George. Schaum’s Outline of Biology. New York: McGraw Hill, 2009. www.google.com/images