![]() Complex hormonal regulations are definitely involved in the process. Here also the basipetal differentiation of bud traces occurs by the addition of vascular elements formed by vascular cambium.įactors determining the initiation and organization of cells into a bud meristem are mainly the hormone and the interaction between buds and subtending leaves. Sometimes the dormant axillary buds are removed further as a result of secondary growth of the main shoot. traces originate in the bud and gradually extend towards the vascular strand of main axis. The differentiation of bud traces in this case is also basipetal, i.e. In this case bud traces differentiate through partly differentiated or vacuolated ground tissues. In some species axillary bud arises in the axil of older leaves. the differentiation of bud trace is basipetal. Careful observation reveals that bud trace first originates in the bud primordium and then gradually extends towards the vascular strand of main axis, i.e. If the bud primordia originate close to apex, the bud traces differentiate earlier than the vacuolation of peripheral meristem.Īt this stage the bud trace appears as meristematic strand lying between the vascular-tissues of main axis and protruding bud. These vascular traces are referred to as bud trace or branch trace. 24.1 B) is followed by the appearance of the leaf primordia beginning with the prophyll.Īxillary buds are connected by vascular traces to the vascular strands of main axis. Regarding the function it is suggested that the cells of shell-zone divide and give an active upward thrust to the developing bud to protrude above the surface. These layers are more or less parallel to each other and are designated as shell-zone because of its shell-like configuration (Fig. As a result a meristematic zone composed of a series of curved layers are formed. This orderly division occurs at base and on lateral side of the incipient bud. In potato plant it is observed that, during the initiation of axillary bud, the divisions are quite regular. In Ulex the lateral buds develop as thorns. These buds are of unequal size and have different potentialities of growth. In Alternanthera philoxeroides two axillary buds arise at a node from the opposite leaves. In the axil of all leaves of a shoot, bud may not be formed, but in some species they arise sporadically or in a regular sequence. In unusual cases axillary bud may arise from the subtending leaf of the first plastochron (ex. This meristem remains dormant or inhibited until stimulated to form meristem of axillary bud. This isolated group of meristematic cells is designated as detached meristem. In some cells vacuoles appear and these differentiated cells separate a group of meristematic cells from the shoot apical meristem. origin from meristematic cells) the cells are continuous with the shoot apical meristem. ![]() This phenomenon can be interpreted as dedifferentiation when the meristematic activity is resumed in differentiated cells. At the time of bud formation, these parenchyma cells regain the power of cell division and form the meristem of axillary bud. In the derivatives of apical meristem, vacuoles appear and thus partly or fully differentiated parenchyma tissues are formed. In the former case the cells owe their origin from the apical meristem. Such bud arises either from differentiated cell like parenchyma or from meristematic cells present at the internode. In some species lateral bud is formed in the axil of older leaves. It happens when the axillary bud attains a position some distance away from shoot apical meristem due to normal growth of shoot. Normal growth and development do not occur immediately. Vacuoles appear in certain cells situated above the axillary meristem and these cells separate the bud meristem from apical meristem.Īs growth continues the bud meristem begins to give rise to leaf primordia. Later the elongation of internodes separates them from each other. Initially the bud meristem is formed in continuity with shoot apical meristem. As a result, the apical meristem of lateral branch is organized resembling that of the parent shoot and elevated above the surface. These cells possess all the characteristics of meristematic cells and divide in various planes, predominantly anticlinal and periclinal. At this level the outer cells of apical meristem divide anticlinally and the cells, thus formed, delimit the meristem of axillary bud from apical meristem. Champagnat (1961) reported epidermal origin of axillary buds.īud primordia usually arise later than the subtending leaves, which are commonly the second or third plastochron. foliar or axial the buds arise exogenously in relation to superficial tissues. Whatever may be the place of origin, i.e. In most cases bud primordia arise on stem at the axil of leaf primordia and sometimes may be displaced towards the leaf base during growth.
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