S1 nuclease A nuclease, purified from the filamentous fungus Aspergillus oryzae, that specifically degrades unpaired (single-stranded) RNA or DNA to 5' mononucleotides. It is used to remove the sticky ends of restriction fragments and to assess the extent of a hybridization reaction by removing unpaired regions. In S1 mapping, the coding region of a gene is detected by performing mRNA-DNA hybridization and removing unpaired DNA with S1 nuclease.
savanna Grassland with scattered trees or shrubs; often a transitional type between true grassland and forestland, and accompanied by a climate with alternating wet and dry seasons.
scale up To make the transition from small-scale production to production of large industrial quantities.
scalping (1) In seed processing: Removal of material larger than the crop seed. (2) Of turf: Removal of an excessive quantity of green shoots at any one mowing, resulting in a stubbly, brown appearance due to the exposed stems, stolons, and dead leaves.
scarifyingSee vertical mowing.
scorchingSee scald.
sealed storage Storage in a sealed container; usually refers to airtight (hermetic) storage.
secondary tillage Tillage that works the soil to a shallower depth than primary tillage, providing additional pulverization; levels and firms the soil, closes air pockets, kills weeds.
seed (1) A mature (ripened) ovule consisting of an embryonic plant and a store of food (stored in the endosperm, in some species), all surrounded by a protective seed coat. (2) To sow or plant seed (e.g., broadcasting or drilling of small-seeded grasses and legumes or other crops).
seed cotton Cotton, as harvested and before ginning, consisting of seeds with the fibers attached and usually including measurable amounts of foreign matter.
seed index The weight in grams of 100 seed.
seed mat A fabricated mat with seed (and fertilizer) applied to one side; the mat serves as a vehicle to (i) apply seed and fertilizer, (ii) control erosion, and (iii) provide a favorable microenvironment for seed germination and establishment.
seed multiplication The aggregate of all practices required to grow a plant to maturity and produce seed, including those practices necessary for harvesting and preparing seeds for subsequent plantings.
seed processing The operations involved in preparing harvested seed for marketing.
seed set The formation of seeds or seed pods on the parent plant.
seed stocksSee stock seed.
seed vigor Those seed properties that determine the potential for rapid uniform emergence and development of normal seedlings under both favorable and stress conditions.
seedling A young plant grown from seed.
seedling, normal A seedling possessing the essential structures indicative of the ability to produce plants under favorable conditions.
selected seed Selected seed is a class of tree seed that is the progeny of rigidly selected trees or stands of untested parentage that have promise but not proof of genetic superiority, and for which geographic source and elevation shall be stated on the certification label.
selective medium Nutrient material constituted such that it will support the growth of specific organisms or genotypes while inhibiting the growth of others.
semiarid turfgrass Turfgrasses adapted to grow and persist in semiarid regions without irrigation (e.g., buffalograss, gramagrasses, and wheatgrasses).
senescence (1) The developmental stage during which deterioration occurs leading to the end of functional life of an organism or organ. Sometimes defined from specific criteria such as a decline in chlorophyll or dry weight. (2) More generally, a slowing in the rate of growth of a plant or plant organ, usually due to old age.
sequencing (1) The determination of the order of nucleotides in a DNA or RNA molecule. (2) The determination of the order of amino acids in a polypeptide chain.
set stocking The practice of allowing a fixed number of animals on a fixed area of land during the time when grazing is allowed.
sexduction The transfer of F' particle to F- bacterial cells in a process similar to transduction.
shattering (1) A condition whereby seeds drop to the ground prior to harvest. (2) A method of turf cultivation involving fragmentation of a rigid or brittle soil mass, usually by a vibrating mechanical mole device.
shoot cultureSee shoot-tip culture.
shoot-tip culture The culturing of a structure consisting of the shoot apical meristem plus one to several primordial leaves, usually measuring from 0.1 to 1.0 mm in length. Usage: In instances where more mature leaves are included, the structure may measure up to several centimeters in length and is more properly called a shoot culture. Synonym: apex culture.
short-lived perennial Turfgrasses normally expected to live only 2 to 4 years.
shrubland Land on which the vegetation is dominated by shrubs.
shuttle vector A plasmid constructed to have origins for replication in two hosts so that it can be used to transfer genes from one organism to another. Synonym: bifunctional vector. See also vector.
silage Forage preserved in a succulent condition by partial anaerobic, acid fermentation.
silage, additive Material added to forage at the time of ensiling to enhance favorable fermentation process.
single cross The first generation of a cross of two inbred lines, an inbred line and a foundation backcross, or of two foundation backcrosses.
single-seed descent A pedigree method for producing inbred lines in which each resulting line can be traced through a single plant in each preceding generation of inbreeding.
single-stranded Of nucleic acid molecules: consisting of only one polynucleotide chain.
site-specific Of a process or enzyme: acting at a defined sequence within a DNA or RNA molecule. Type II restriction endonucleases are site-specific endonucleases and the recombination systems encoded by some transposable elements are site-specific, as is the integration of phage into the Escherichia coli chromosome.
slicing A method of turf cultivation in which vertically rotating, flat tines slice intermittently through the turf and the soil.
sliver A continuous strand of loosely assembled fibers, approximately uniform in cross-sectional area and without twist.
sliver, drawing A sliver produced by a draw frame.
slow-release fertilizer Fertilizer with a rate of dissolution less than is obtained for completely water-soluble fertilizers; may involve compounds that dissolve slowly, materials that must be decomposed by microbial activity, or soluble compounds coated with substances highly impermeable to water. Synonyms: controlled-availability, controlled-release, delayed-release, metered-release, and slow-acting fertilizer. Compare quick-release fertilizer. See also response rate.
sod cutter A device to sever turf from the ground; the length and thickness of the cut are adjustable. See also sod harvesting.
sod heating Heat accumulation in tightly stacked sod; may reach lethal temperatures.
sod production Culture of turf to a quality and maturity that allows harvesting and transplanting. Synonym: sod rooting.
sod strength The relative ability of sod to resist tearing during harvesting, handling, and transplanting.
sodding Planting turf by laying sod.
soft endospermSee chalky.
soil mix A prepared mixture used as a growth medium for turfgrass.
soil probe A soil-sampling tool, usually having a hollow cylinder with a cutting edge at the lower end.
soil shredder A machine that crushes or pulverizes large soil aggregates and clods to facilitate uniform soil mixing and topdressing application.
soilingSee topdressing.
somaclonal variation Variation that occurs and accumulates in cultures of cells and tissues; it may be either genetic or epigenetic in basis. When the rate of variation exceeds the normal mutation rate of that species or genotype in vivo, the variation may be said to arise as a result of growth or manipulation in vitro, and may be the result of growth in unorganized states.
somatic cell hybridization The fusion of plant protoplasts derived from somatic cells that differ genetically.
somatic embryogenesis Formation of a somatic embryo. See also embryogenesis.
source-identified seed Source-identified is a class of true seed defined as seed from (i) natural stands with known geographic source and elevation, or (ii) a plantation of known geographic location, as specified in the standards of the various certifying agencies.
Southern hybridizationSee Southern blot.
span length Of cotton: The distance spanned by a specified percentage of the fibers in a fibrograph test beard.
spectroscopy Observation by means of an optical device (spectroscope) of the wavelength and intensity of electromagnetic radiation (light) absorbed or emitted by various materials. Theoretical interpretation of well-defined wavelengths of elements (often present in only minute quantities) in obtained spectra leads to knowledge of atomic and molecular structure. See also nuclear magnetic resonance spectroscopy.
spheroplast A bacterial, yeast, or sometimes plant cell from which the cell wall has been nearly removed, in contrast to a protoplast, in which the cell wall has been entirely removed.
spiking A method of turf cultivation in which solid tines or flat, pointed blades penetrate the turf and soil surface.
split gene A gene in which the coding sequence is interrupted by a number of noncoding regions called introns.
spongy turfSee puffiness.
spoon, coring A method of turf cultivation involving curved, hollow, spoonlike tines that remove small soil cores and leave openings in the sod.
spot sodding The repair of small areas of damaged turf using plugs of small pieces of sod.
sprig (1) A stolon, rhizome, tiller or combination used to establish turf. (2) To plant sprigs.
spring green-up The initial seasonal appearance of green shoots as spring temperature and moisture conditions become favorable, thus breaking winter dormancy.
Stage II A step in in vitro propagation characterized by the rapid numerical increase of organs or other structures.
Stage IV A step in in vitro propagation characterized by the establishment in soil of a tissue culture-derived plant, either after undergoing a Stage III pretransplant treatment, or, in certain species, after the direct transfer of plants from Stage II into soil.
stalk diameter The diameter of a stalk, usually at a designated node or internode.
stalk tunneling Longitudinal tunnels in plant stalks produced by insects (e.g., by sugar cane borer, lesser corn stalk borer.
standard atmosphere In textile testing: Air maintained at a relative humidity of 65% and a temperature of 70 °F (21 +/- 1 °C).
staple (1) Natural or cut fibers or cut lengths from filaments. (2) To classify cotton fiber samples by length.
starch granule The fundamental unit in which starch is deposited in the storage tissue of many higher plants. It is paracrystalline cold-water insoluble, with a characteristic size and shape depending on the species of the plant that produced it.
sticky ends The single-stranded DNA ends left on a restriction fragment by many Type II restriction endonucleases. These unpaired regions are available for hybridization with complementary ends on other fragments during gene cloning experiments. Synonym: cohesive ends. Compare blunt ends.
stock seed Supply of seed, tubers, or roots reserved for planting and used as a source of germplasm for maintaining and increasing seed of crop varieties or genetic lines. Synonym: seed stocks.
stocking density The relationship between the number of animals and the specific unit of land being grazed at a given time.
stocking plan The number and kind of livestock assigned to one or more given management areas or units for a special period.
stocking rate The relationship between the number of animals and the grazing management unit utilized over a given time period.
stolon nursery An area used for producing stolons for propagation.
storage Reversible accumulation of materials in localized organelles, cells, or organs. Storage implies that the material is available for subsequent mobilization under some conditions. See also reserves.
strainSee cell strain.
strain 2 A selection within a variety lacking clear-cut morphological differences, but having distinguishing physiological or agronomic qualities such as drought resistance, superior yield, etc.
strength, breaking The maximum internal cohesive forces of a material that resists rupture during a tensile test.
stress An environmental condition potentially harmful to an organism, and causing a reduction in normal functions. See also resistance.
stress, tensile The resistance to deformation developed within a specimen subjected to tension by external force.
strip sodding Laying of sod strips spaced at intervals, usually across a slope; turf establishment depends on spreading of the grass to form a complete cover; sometimes the area between the strips is seeded.
strong promoter A promoter for which RNA polymerase has a high affinity, thereby directing the synthesis of large amounts of mRNA from the corresponding gene(s).
stubble mulch Crop residues left essentially in place after tillage, as a surface cover during fallow and the growing of a succeeding crop.
subclone The cloning of smaller DNA fragments from a larger DNA insert that has already been cloned in a vector.
substrain A cell strain derived from a parent strain by isolating a single cell or groups of cells having properties or markers not shared by all cells of the parent strain.
substrate (1) The substance acted on in a chemical reaction. (2) A culture medium.
summer syndromeUsage: An unsatisfactory term for fescue toxicosis, since it implies a seasonal restriction. Acceptable if limited to signs observed in the summer. Summer slump is a vernacular synonym, also unsatisfactory.
supplemental feeding Of animal feeding: Supplying concentrates or harvested feed to correct deficiencies of the pasture diet. Often erroneously used to mean emergency feeding. Compare maintenance feeding.
suppressor mutation A mutation that counteracts the effects of a prior mutation, either in the same or in a different gene. An intragenic suppressor mutation can compensate for a prior frame-shift mutation by restoring the original reading frame in the gene. An extragenic suppressor mutation is usually a gene coding for a mutant tRNA with an altered anticodon. The mutant anticodon does not recognize a chain-terminating mutation, which would result in synthesis of a truncated polypeptide, but rather continues translation due to insertion of either the correct original amino acid or an acceptable substitute into the polypeptide, which retains at least partial function.
surplus assimilatesSee reserves.
sustained yield The continuation of desired forage or animal production.
swathing The cutting or pulling of a crop into a windrow to dry and/or to facilitate harvest.
synchronous culture A culture in which a large proportion (often a majority) of the cells are in the same phase of the cell cycle at the same time.
synthetic turfSee artificial turf.
syringing Spraying turf with small amounts of water to (i) dissipate accumulated energy in the leaves by evaporating free surface water, (ii) prevent or correct a leaf water deficit, particularly wilt, and (iii) remove dew, frost, and exudates from the turf surface.