First Insights Into Micromorphology of Needle Epicuticular Waxes of South-Eastern European Pinus Nigra J. F. Arnold Populations

Abstract

This is the fi rst insight into the fi ne structure of the epicuticular wax crystalloids found on the adaxial surfaces of needles from three Pinus nigra subspecies (ssp. nigra, ssp. banatica (Borbás) Novák, and ssp. pallasiana (Lamb.) Holmboe) growing wild in the southeastern Europe. In general, the main wax crystalloids in P. nigra taxa were tubules, fairly dense, with reticular aspect and restricted to suprastomatal chambers. The P. nigra needles have amorphous wax-smooth layers, granules, alone tubes lying on the surface, tubes slightly fused to each other, tubes fused together, and longitudinally aggregated rodlets. The only diff erence between the studied P. nigra samples was related to the presence of longitudinally aggregated rodlets in the medial part of adaxial needle surfaces. The micromorphological characters found using SEM are compared and discussed from fundamental and applicative aspects.

Testing Explant Sources, Culture Media, and Light Conditions for the Improvement of Organogenesis in Pinus ponderosa (P. Lawson and C. Lawson)

“…In this sense, Boddi et al [ 58 ] described teeth or spine-like structures in transverse sections as more elongated cells with cytoplasmic content differing from the adjacent epidermic cells for thicker walls; however, the relevance of these structures is unknown. A scanning electron micrograph revealed stomata arranged in parallel and as uniseriate bands, which is in accordance with the work described for P. nigra by Mitic et al [ 59 ]. Similar to that observed in P. halepensis , [ 58 ] large and ovoidal stomata were detected in this study.…”

“…The teeth structures on the needle surface were morphologically similar to those found in primary needles of P. halepensis and P. nigra [ 58 , 59 ]. In this sense, Boddi et al [ 58 ] described teeth or spine-like structures in transverse sections as more elongated cells with cytoplasmic content differing from the adjacent epidermic cells for thicker walls; however, the relevance of these structures is unknown.…”

Structural changes in needle epicuticular waxes of Balkan Abies species in relation to natural weathering

“…Such a restriction of the crystalloids to the needle surface with stomatal complexes suggested that the structural wax originates associated with the stomatal complex. In accordance, many studies have shown that wax tubules on needles are not distributed evenly in Pinales, considering their tendency to be concentrated near stomata and between them in the stomatal rows (Crossley & Fowler 1986;Kim et al 2011;Ivănescu et al 2008;Mitić et al 2017). Epicuticular wax tubules on A. alba needles are deposited only on the abaxial surface where stomatal complexes occur (Bačić & Popović 1998), just as observed in our study.…”

“…In accordance, our study showed increasing degradation of tubules on Abies needles with the needle aging. These changes in the appearance of structural waxes are part of the natural aging process, and gradually all structural wax degrades to granules or amorphous crusts (Mitić et al 2017).…”

“…Certain wax crystalloids were often positively correlated with the presence of specific components within the wax, leading to several papers dealing with the interrelation between chemical composition and micromorphology of crystalloid types (e.g., Baker 1982;Walton 1990;Bianchi 1995). For example, the secondary alcohol nonacosan-10-ol is the main component of cuticular waxes of species from the Pinaceae family (Riederer 1989, Barthlott et al 1998, and its biological importance is mainly ascribed to the role of shaping the crystalloids in the form of characteristic tubules on the conifer needles (Matas et al 2003;Jeffree 2006;Mitić et al 2017). Tubules are cylindrical, hollow crystalloids with a terminal opening (Barthlott et al 1998).…”