The anatomy of reaction wood was studied in nine naturally growing Japanese hardwood species, all showing eccentric growth on the upper side of their leaning branches. The number of vessels decreased in the xylem of the upper side accompanying the formation of reaction wood. A typical G-layer was not detected in the reaction wood fibers, but an S3 layer was present in all nine species. The cellulose microfibril arrangement with an S helix was similar in the S3 layers of both reaction and opposite wood fibers. A decrease of lignin content occurred in the reaction wood fibers in all nine species. The coniferyl and sinapyl aldehyde units in the lignins were strongly reduced in the S2 layer of reaction wood fibers of four species, i.e., Euscaphis japonica, Rhododendron wadanum, Clerodendron trichotomum, and Daphne odora, and much less so in five other species, i.e., Viburnum dilatatum, Enkianthus subsessilis, Euonymus alatus, Ilex macropoda, and Ilex crenata. The syringyl content was lower in the S2 layer of reaction wood fibers than that in opposite wood of all nine species. On the other hand, chemical analysis of lignin using the acetyl bromide method showed that, among the nine species, lignin content was reduced most strongly in Clerodendron trichotomum. Tension wood-like characteristics are present on the upper side of leaning branches in all nine species, except that G-fibers are absent.
An efficient and reproducible procedure was established for direct shoot regeneration of Solanum surattense Bum. using internodal explants. The shoot regeneration efficiency on Murashige and Skoog (MS) medium supplemented with 6benzylaminopurine (BAP) was superior in compared to 6furfurylaminopurine (Kn). The highest mean number of shoots per explant was recorded on MS medium containing 0.5 mgl-1 BAP. BAP alone was more effective for shoot regeneration than combination of BAP and -naphthaleneacetic acid (NAA). The number of shoot per explant was highest in the 4 th subculture and then it was remained stable up to 6 th subculture. The shoot number drastically reduced from 7 th subculture when explants were repeated subculturing up to 8 th subculture. Hundred percent adventitious shoots were rooted successively on half strength MS medium fortified with 0.05 mgl-1 NAA. At about 90% of the in vitro-propagated plantlets survived when they were transferred to ex vitro conditions for acclimatization.
A plantlet regeneration protocol was developed on pot-grown mature plants of Elaeocarpus robustus Roxb. cv. Dwarf from nodal and leaf explants. The best yield of adventitious shoots was achieved from the leaf-derived calli in a modified MS (MMS 1 , half strength of major salts, full strength of minor salts, and vitamins) medium containing 4.0 lM BA ? 4.0 lM Kn ? 0.5 lM NAA ? 15% coconut water (CW). The shoot multiplication rate was amplified about twofold per culture after the addition of 15% CW to the medium. The rate of shoot multiplication reached maximum at the 5th subculture, and it maintained this rate throughout the 3 subsequent subcultures. The best rooting in vitro was investigated by subculturing the microcuttings in an MMS 2 (half strength of both major salts and minor salts and full strength of vitamins) medium containing 1.0 lM IBA in the dark for one initial week at 30°C, followed by subculturing them in a plant-growth regulator (PGR)-free medium in the light. The plantlets raised in vitro were successfully established under ex vitro conditions.
Due to a non-vertical orientation of the stem or branch, which may begin as responses of prevailing winds, snow, slope, or asymmetric crown shape, a specialized wood tissue forms, is called "reaction wood". In hardwood species, the reaction wood tends to form on the upper side of a leaning stem or branch, is known to as "tension wood". It is usually related with eccentric growth and changes in structure and chemistry of wood. During the formation of tension wood many changes found in wood cells, especially in wood fibers. The changes of wood properties in tension portion result different shrinkage characteristics during drying, creates a serious problem at adjacent portion of normal wood. However, tension wood is problematic in the hardwood industries and this wood is economically less valued. However, the studies on tension wood are necessary for beneficial applications in the wood industries sectors as well as research sectors. The knowledge on tension wood anatomy is still a matter for tree growers and timber processors, especially who are often involved in the furniture making. Besides, the understanding of tension wood formation provides a unique opportunity to obtain information on the molecular and biochemical mechanisms in the expression patterns of genes/proteins. The studies on reaction wood anatomy are not enough that we concluded any model. This review describes the features of fibers in tension wood todate, including secondary wall layers structure. Until date, six types structure of secondary cell wall layers for tension wood fibers such as,
Abstract:The stem and leaf anatomical studies of Euphorbia hirta L. were conducted for finding identical traits. The fresh hand sections were stained with safranin and examined under light microscope. Cross section of the stem has a circular shape where epidermis was uniseriate and isodiametric. Cortex was distinctly formed with about 5-6 rows composed of chlorenchyma and found laticifers. Tracheary elements were resembled by vessels and trachieds. In most cases, some pith cells were filled laticifers at young stage and it has a distinct gap or central cavity at maturation stage. In leaf, the epidermis was uniseriate, regular, thin walled, usually similar in diameters and covered with thin cuticle layer. Multicellular uniseriate or gland-like trichomes occur in rugose hairs at epidermis. Mesophyll was differentiated into palisade and spongy layers, was composed of parenchyma cells. The palisade layer assembled with 2 rows of cells. The spongy layer thickness was different around the midrib region, compared with other parts, has 2-6 rows of cells. Laticifers were present at the middle part of the mesophyll. Xylem elements in midrib initiated perfectly and composed of many straight rows of mainly vessels where the phloem elements were abundant and occupied a good part of the vascular bundle as a semicircle shape. The stem and leaf anatomy of this species studied here showed laticifers in cortex zone and pith cells, and middle part of the mesophyll, respectively, was a taxonomic trait for this species.
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