Date palm rachis as a raw material for wood composite industry: anatomical characteristics

Abstract

This study is focused on the internal structure of leaf midrib (rachis) of some male tress of certain date palm cultivars, namely Khalas, Naboat-Saif, Sillej and Sukkary, common to Saudi Arabia. It takes into consideration the structure, dimension and abundance of vascular bundles (VBs), vessel lumen diameter, relative proportion of fibers and vessels in the vasculature at the basal and the middle parts along the length of the rachis. A large number of conjoint, collateral and closed VBs of varying sizes, embedded in the parenchymatous ground tissue, are normally present. The xylem in the VB often contains 6–15 protoxylem and 2–3 metaxylem vessels as seen in cross-sectional view. Vascular bundles have fiber caps, of which the upper ones were quite thicker than the lower (inner) ones in general. Cultivars Khalas and Sukkary are superior in having the highest midrib cross-sectional area (17.1 cm2 and 16.8 cm2, respectively). Moreover, Khalas have the highest fiber area fraction (17% and 25%), while Sukkary a highest vessel density (16–17 per VB) in both the basal and middle positions at the rachis. Cultivar Naboat-Saif is superior in having a high VB density (130 and 194 per cm2), narrowest vessels (42.4 µm and 53.5 µm) and thickest vessel wall (4.23 µm and 4.45 µm, respectively) both in the basal and in the middle position of the rachis length.