Development of lateral meristem and pattern of secondary growth in stems and roots of Spinacia oleracea Linn (Amaranthaceae)

Abstract

AbstractDevelopment of lateral meristem and pattern of secondary growth in the stems and roots of Spinacia oleracea Linn (Amaranthaceae) were studied anatomically. Maturing stems and roots increased in thickness by developing successive rings of cambia which produce secondary vascular elements embedded in the groundmass of thin walled parenchymatous conjunctive tissues. Second ring of the cambium was originated outside the first ring of the cambium and gave rise to parenchyma cells and sieve tube elements on the outer side whereas it gave rise to conjunctive tissue and secondary xylem on the inner side. Prior to the development of second ring of cambium, parenchyma cells located outside to the previous cambium dedifferentiated and acquired meristematic property which led to the formation of meristematic bands of radially arranged cells. Later on each successive ring of cambium developed in similar fashion as described above. The groundmass of the stems and roots was mostly composed of thin walled conjunctive tissue on both the outer and inner side of each cambium, whereas formation of thick walled conducting elements of secondary xylem and secondary phloem remained restricted to the small segments of the vascular cambium. Secondary xylem was composed of vessel elements, tracheids and libriform fibres whereas secondary phloem comprised of sieve tube elements, companion cells and axial parenchyma with no typical rays even in the mature stems. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)