Size variation in the vascular cambium and its derivatives in two Alstonia species

Abstract

RESUMO -(Variação em tamanho do cambio vascular e seus tecidos derivados em duas espécies de Alstonia). Duas espécies de árvores tropicais (Alstonia venenata Br. e Alstonia neriifolia Don. -Apocynaceae) foram estudadas para detectar variação em tamanho de diversos elementos do cambio e seus tecidos derivados. Embora as condições de clima e edaficas destas duas espécies fossem identicas, as dimensões das iniciais fusiformes e os elementos derivados destas foram maiores em A. venenata do que em A. neriifolia. As iniciais radiais são retangulares em A. venenata porem são isodiamêtricas em A. neriifolia. Foi observado aumento substancial no comprimento das células do floema e xilema quando comparadas com as células mãe. Alongamento máximo foi observado nas fibras do xilema durante a diferenciação das respectivas iniciais fusiformes.Palavras-chave: comprimento das iniciais funsiformes, iniciais radiais, elementos do tubo crivado, elementos de vaso, fibras do xilema, Alstonia venenata, Alstonia neriifolia ABSTRACT -(Size variation in the vascular cambium and its derivatives in two Alstonia species). Two tropical tree species viz.Alstonia venenata Br. and Alstonia neriifolia Don. (Apocynaceae) were investigated to detect size variation in different elements of the cambium and its derivative tissues. Although these two species were grown under identical climatic and edaphic conditions, fusiform initial dimensions and the elements derived from them were larger in A. venenata than in A. neriifolia. Ray initials are rectangular in A. venenata but isodiametric in A. neriifolia. An appreciable increase in length was observed in the phloem and xylem ray cells when compared to the mother cells. Maximum elongation was observed in xylem fibers during differentiation from the respective fusiform initials.

Bark anatomy and cell size variation in Quercus faginea

“…ex Delile and P. spicigera (Iqbal & Ghouse, 1983), but the inverse was shown by Trockenbrodt (1994) in Q. robur with longer fibres in the top of the tree. Fibre length depends also on the degree of intrusive growth (Ghouse & Siddiqui, 1976;Khan & Siddiqui, 2007;Lev-Yadun, 2010) and on maturation and outlines of surrounding cells (Jura-Morawiec, 2008), which can justify the different patterns of axial variation described for other genera, i.e. Eucalyptus (Quilhó et al, 2000) and Acacia (Tavares et al, 2011).…”