Latent root primordia in poplar stems |
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Authors: | Mária Luxová A Lux |
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Institution: | (1) Institute of Experimental Biology and Ecology, Slovak Academy of Sciences, Dúbravská cesta 14, 885 34 Bratislava, Czechoslovakia |
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Abstract: | Root primordia initiate in poplar stems in the secondary growing parts, that is in the parts where the elongation growth is
terminated and the leaves are mature. Their initiation is connected with the occurrence of unusual biseriate, rarely multiseriate
rays. A small cell group in the secondary phloem is initiated by cell division of the ray. It gradually enlarges by continuing
cell division, by the addition of cells adjacent to the cell group and by cambial activity. Thus, a hemispherical root primordium
is formed, for which a permanent occurrence of reserve lipids is characteristic. In stems several years old the intraprimordial
mitotic activity is rhythmically renewed together with the cambium function renewal. Latent root primordia slightly enlarge
with the passing years, whereas mainly the cells localized in their centre divide. Further organization and root histogenesis
was not observed either in older root primordia. Adjacent to root primordia, cambial initials produce the secondary xylem
elements increasingly. Xylem protuberances are thus formed under root primordia. Primordia initiation is most frequent within
the first year of stem development, though they can also initiate in later years. |
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