Simple Fruit - A fruit that is formed from one ovary.

Simple Leaf - A leaf having the lamina in one piece. It may be lobed, but the lobes never reach the mid-rib.

Simple Pit - A pit that is not having border. For example, it is found in certain parenchyma cells, extraxylary fibers and sclerieds. Compare bordered pit.

Simple Sorus - A Sorus having one sporangium.

Simple Tissue - A tissue made up of cells all of the same kind.

Simple Umbel - An umbel in which the flower-stalks are arising directly from the top of the main stalk.

Single Cell Protein (SCP) - A protein which is produced by unicellular organisms for animal and human consumption. Much research is being done to develop suitable industrial plants for large scale culture of certain bacteria, fungi and algae and many products are available e.g., Pruteen.

Single Factor Inheritance - Said of the determination of a character by one factor which may exist in various allelic forms Mendelian factors and inheritance are examples of single factor inheritance.

Sink - Used for .describing a site within an organism or cell where a particular substrate or catalyst is being utilized. For example, mitochondria act sink for oxygen and chloroplasts for carbon dioxide.

Sinuate - (1) Referring to the margin divided into wide irregular teeth or lobes, which are separated by shallow notches. (2) Refers to the gills of agarics which curve suddenly on reaching the stripe.

Siphonostele - A stele having the xylem and phloem arranged in the form of concentric cylinders around a central pith. It is ectophloc if the xylem is nearest the pith, and amphiphloic if the phloem is nearest the pith.

Sliding Growth - Refers to the movement of developing tracheids and vessels along their mutually touching longitudinal walls as the cells elongate.

Slime Bacteria - Refers to the members of order Mycobacterials that are flexible and creeping in habit. They do not have rigid cell wall and flagella. However, they are moving by gliding across the substrate. Most members are terrestrial and differ from other bacteria in producing resting cells called microcysts that are usually borne in fruiting bodies. Many are soil saprophytes.

Slime Flux - Refers to an exudation of a watery solution of sugars and other substances from tress which are wounded, or attacked by parasites.

Slime Moulds - Including members of class Myxomycota that are fungus-like. They consist of naked mass of protoplast called plasmodium. In this class there are about 500 species of about 70 genera and usually occurred on decaying vegetation. Various forms in life-cycle (See swarm cell, myxamoeba, plasmodium) show characteristics of animals, notably ingestion of solid food.

Smooth Endoplasmic Reticulum - Said of endoplasmic reticulum on which no ribosomes get attached giving it smooth appearance.

Smuts - Refer to the diseases of plants that are caused by members of fungal order Ustilaginales that are producing characteristic masses of black spores usually on the host. In covered smuts (e.g., covered smut of barley by Ustilago hordei), mature spore mass is left within the Sorus for sometime, often until sorus gets liberated from the host. In loose smuts (e.g., loose smut of wheat by U.nudo), spores are uncovered and form mass of black powder. This term is also used sometimes for describing fungi that cause the smut disease.

Society - Refers to a minor community within a consociation. It arises as a result of local variation in the environment, and dominated by species other than the consociation dominant.

Soft Rot - A disease which is caused by fungi or bacteria in which tissues of affected plant become soft. Diseases are most often caused in stored fruits and vegetables by fungus Rhizopus and bacterium Erwinia, especially in humid and badly ventilated conditions.

Soil - Refers to the superficial layer of materials which is covering earth crust. It denotes the natural medium in which plants anchor and from which they derive water and nutrients. Soil is having soil minerals derived from weathering of rocks, soil organic matter derived from death. Decay and decomposition of living matter, soil water and soil air. Various soil microorganisms occur in the soil.

Soil-Borne Diseases - Refer to any plant disease that originates from inoculum in the soil e.g., damping - off club root. Their control is difficult.

Soil Profile - Refers, to the arrangement of horizontal payers as observed in the vertical section of the soil body at a place. The layers are called soil horizons which are different in thickness, colour, texture and composition in different soil types.

Soil Structure - Refers to the shape and arrangement of large soil aggregates in the soil. Mineral particles in soil form large units called peds which may be having different shapes such as cubical, spherical, columnar, prismatic, laminar and granular. The shape and size of peds and, their arrangement decide the pore space in the soil and thus ascertain the amount of soil water and soil air.

Soil Texture - Defining the roughness of soil which is decided on the basis of relative proportions of different sized mineral particles in it. A soil which is having atleast 85% sand and not more than 10% clay, remaining being silt is called sandy soil which is having more than 80% silt and less than 12% clay, rest being sand is called silt soil (loam) and which is having 60-80% clay, 10-15% sand and rest being silt is called clay soil. There are some various intermediate categories also. Soil texture helps to known the soil water, soil aeration, water holding capacity, capillarity etc., in the soil. Ploughing, harrowing and rolling are known to alter soil texture to some extent by altering the soil structure.

Solarization - Refers to the temporary stopping of photosynthesis in a leaf which has been exposed. to strong light for a long time.

Solenostele - Refers to the vascular tissue in plant in which the phloem lies on both sides of the xylem.

Solonchak - A saline soil which is developed. under hot, dry conditions, where the salts accumulate near the surface.

Solonetz - Refers to solonchak which has been leached. of its salt, so that the surface exchangeableions are not sodium, but calcium or magnesium.

Somatic - Used for describing all parts of a plant, except the germ mother-cells and gametes.

Somatic Apogamy. Refers to the development of the saprophyte from the tissues of a gametophyte, without involving the fusion of nuclei. It therefore has the same chromosome number as the gametophyte.

Somatic Cell - Refers to any cell of the vegetative body of the organism other than reproductive cell i.e., spore, gamete or their precursors.

Somatic Hybridization - Refers to the production of cells, tissues or organisms by involving fusion of non-gametic nuclei. It is possible to induce the phenomenon under laboratory conditions in cells that normally never fuse together and finds use in plant breeding or genetics. It may also occur naturally, especially in fungi.

Somatic Mitosis - The division of a metabolic nucleus.

Somatic Mutation - A mutation in a somatic cell, rather than in a germ-cell.