Laimosphere
Encyclopedia
The laimosphere is the microbiologically enriched zone of soil
that surrounds below-ground portions of plant stems; the laimosphere is analogous to the rhizosphere
and spermosphere. The combining form laim- from laimos (Greek: λαιμός) denotes a connecting organ (neck) while -sphere indicates a zone of influence. Topographically, the laimosphere includes the soil around any portion of subterranean plant organs other than roots where exuded nutrients (exudates) stimulate microbial activities. Subterranean plant organs with a laimosphere include hypocotyl
s, epicotyl
s, stem
s, stolon
s, corm
s, bulb
s, and leaves
. Propagules of soil-borne plant pathogens, whose germination is stimulated by a plant exudates in the laimosphere, can initiate hypocotyl and stem rots leading to "damping-off". Pathogens commonly found to cause such diseases are species of Fusarium, Phoma, Phytopthora, Pythium, Rhizoctonia and Sclerotinia.
Fig. 1. A diagram denoting the location of the laimosphere, rhizosphere, and spermosphere of the subterranean organs of a plant (Plant and Soil 37:187-190, 1972).
Fig. 2. Chlamydospores of Fusarium solani f. sp. cucurbitae forming in the laimosphere of a squash hypocotyl, Magyarosy 1973.
Fig. 3 & 4. Early lesion development in the epidermis of a squash hypocotyl caused by Fusarium solani stained with tetrazolium salt, Magyarosy 1973.
Fig. 5. Diagram of hypocotyl stem rot leading to "damping-off" caused by Rhizoctonia solani (Univ.Calif. Agr. Exp. Sta. Service Manual 23, 1957).
Baker, K.F. 1957. The U.C. system for producing healthy container-grown plants. Univ.Calif. Agr. Exp. Sta. Service Manual 23.
Hancock, J. G. 1977. Soluble metabolites in intercellular regions of squash hypocotyl tissues: implications for exudation. Plant and Soil 47:103-112.
Johnson, L. F., and N. G. Bartley. 1981. Cotton laimosphere populations of microrganisms and their antibiotic effect on Pythium ultimum. Phytopathology 71:884-981.
Kasuya, M., et al. 2006. Induction of soil suppressiveness against Rhizoctonia solani by incorporation of dried plant residues into soil. Phytopathology 96: 1372-1379.
Magyarosy, A. C. 1973. Effect of squash mosaic virus infection on microbial populations around the hypocotyl and chloroplast structure and function. Ph.D. Dissertation, Univ. Calif., Berkeley.
Magyarosy, A., and J. G. Hancock. 1972. Microbial population of the laimosphere of squash (Cucurbita maxima) Plant and Soil 37:187-190.
Magyarosy, A. C., and J. G. Hancock. 1974. Association of virus-induced changes in laimosphere microflora and hypocotyl exudation with protection to Fusarium stem rot. Phytopathology 64:994-1000.
Soil
Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...
that surrounds below-ground portions of plant stems; the laimosphere is analogous to the rhizosphere
Rhizosphere
The rhizosphere is the narrow region of soil that is directly influenced by root secretions and associated soil microorganisms. Soil which is not part of the rhizosphere is known as bulk soil. The rhizosphere contains many bacteria that feed on sloughed-off plant cells, termed rhizodeposition, and...
and spermosphere. The combining form laim- from laimos (Greek: λαιμός) denotes a connecting organ (neck) while -sphere indicates a zone of influence. Topographically, the laimosphere includes the soil around any portion of subterranean plant organs other than roots where exuded nutrients (exudates) stimulate microbial activities. Subterranean plant organs with a laimosphere include hypocotyl
Hypocotyl
The hypocotyl is the stem of a germinating seedling, found below the cotyledons and above the radicle .-Dicots:...
s, epicotyl
Epicotyl
In plant physiology, the epicotyl is the embryonic shoot above the cotyledons. In most plants the epicotyl will eventually develop into the leaves of the plant. In dicots, the hypocotyl is what appears to be the base stem under the spent withered cotyledons, and the shoot just above that is the...
s, stem
Plant stem
A stem is one of two main structural axes of a vascular plant. The stem is normally divided into nodes and internodes, the nodes hold buds which grow into one or more leaves, inflorescence , conifer cones, roots, other stems etc. The internodes distance one node from another...
s, stolon
Stolon
In biology, stolons are horizontal connections between organisms. They may be part of the organism, or of its skeleton; typically, animal stolons are external skeletons.-In botany:...
s, corm
Corm
A corm is a short, vertical, swollen underground plant stem that serves as a storage organ used by some plants to survive winter or other adverse conditions such as summer drought and heat ....
s, bulb
Bulb
A bulb is a short stem with fleshy leaves or leaf bases. The leaves often function as food storage organs during dormancy.A bulb's leaf bases, known as scales, generally do not support leaves, but contain food reserves to enable the plant to survive adverse conditions. At the center of the bulb is...
s, and leaves
Leaf
A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....
. Propagules of soil-borne plant pathogens, whose germination is stimulated by a plant exudates in the laimosphere, can initiate hypocotyl and stem rots leading to "damping-off". Pathogens commonly found to cause such diseases are species of Fusarium, Phoma, Phytopthora, Pythium, Rhizoctonia and Sclerotinia.
Fig. 2. Chlamydospores of Fusarium solani f. sp. cucurbitae forming in the laimosphere of a squash hypocotyl, Magyarosy 1973.
Fig. 3 & 4. Early lesion development in the epidermis of a squash hypocotyl caused by Fusarium solani stained with tetrazolium salt, Magyarosy 1973.
Fig. 5. Diagram of hypocotyl stem rot leading to "damping-off" caused by Rhizoctonia solani (Univ.Calif. Agr. Exp. Sta. Service Manual 23, 1957).
Sources
Atkinson, T. G., et al. 1974. Root rot reaction in wheat resistance not mediated by rhizosphere or laimosphere antagonists. Phytopathology 64:97-101.Baker, K.F. 1957. The U.C. system for producing healthy container-grown plants. Univ.Calif. Agr. Exp. Sta. Service Manual 23.
Hancock, J. G. 1977. Soluble metabolites in intercellular regions of squash hypocotyl tissues: implications for exudation. Plant and Soil 47:103-112.
Johnson, L. F., and N. G. Bartley. 1981. Cotton laimosphere populations of microrganisms and their antibiotic effect on Pythium ultimum. Phytopathology 71:884-981.
Kasuya, M., et al. 2006. Induction of soil suppressiveness against Rhizoctonia solani by incorporation of dried plant residues into soil. Phytopathology 96: 1372-1379.
Magyarosy, A. C. 1973. Effect of squash mosaic virus infection on microbial populations around the hypocotyl and chloroplast structure and function. Ph.D. Dissertation, Univ. Calif., Berkeley.
Magyarosy, A., and J. G. Hancock. 1972. Microbial population of the laimosphere of squash (Cucurbita maxima) Plant and Soil 37:187-190.
Magyarosy, A. C., and J. G. Hancock. 1974. Association of virus-induced changes in laimosphere microflora and hypocotyl exudation with protection to Fusarium stem rot. Phytopathology 64:994-1000.