Comparative study of mycorrhizal susceptibility and anatomy of four palm species

Abstract

A morphological and anatomical study of the root systems of the palm species Brahea armata S. Watson, Chamaerops humilis L., Phoenix canariensis Chabaud and Phoenix dactylifera L. has been carried out to determine possible mycorrhizal colonization sites. Furthermore, the arbuscular mycorrhizal (AM) anatomical types formed by the four palm species in association with Glomus mosseae (Nicol. & Gerd.) Gerdemann & Trappe have been examined. The presence of a continuous sclerenchymatic ring in the outer cortex and aerenchyma in the inner cortex that are anatomical indicators of mycorrhizal nonsusceptibility in all four palm species is observed. The root systems of B. armata and C. humilis present only one group of third-order roots, while the third-order roots of P. canariensis and P. dactylifera may be divided into five different groups: short thick roots, mycorrhizal thickened roots, fine short roots, fine long roots, and pneumatorhizas. Third-order and some second-order roots of B. armata and C. humilis are susceptible to colonization by AM fungi, while only the mycorrhizal thickened roots form mycorrhizas with arbuscules in the Phoenix species. The root system of the Phoenix species also presents AM colonization in fine roots with only intraradical hyphae and spores, but without arbuscules, and pseudomantles of spores anchored in the pneumatorings of the second-order roots, which are described for the first time. The mycorrhizas formed by the four palm species are of an intermediate type, between the Arum and the Paris types, and are characterized by intercalary arbusculate coils and not only by intracellular but also by intercellular fungal growth. Our study suggests that a different degree of adaptation may exist among palm mycorrhizas toward the slow growth of palms and low spore numbers in the soil where they grow.

Arbuscular mycorrhizal inoculation increases biomass of Euterpe edulis and Archontophoenix alexandrae after two years under field conditions

“…Root anatomical features of A. alexandrae and E. edulis are evoked as one factor limiting mycorrhizal colonization. In four palm species, Dreyer et al (2010) observed the presence of a continuous sclerenchymatic ring in the outer and aerenchyma in the inner root cortex, both anatomical indicators of resistance to mycorrhizal colonization. Fischer & Jayachandran (1999) hypodermal layers.…”

How Root Structure Defines the Arbuscular Mycorrhizal Symbiosis and What We Can Learn from It?

“…Unfortunately, no accompanying data have been presented on the mycorrhizal susceptibility and presence of the different AM fungal structures in these root types, although it has been repeatedly suggested that it would be highly revealing to examine root traits by root order in mycorrhizal studies (Valenzuela-Estrada et al 2008). Many studies have shown that the root orders most susceptible to being colonised are the higherorder or ultimate roots (Janos 1977;Nadarajah 1980;Fisher and Jayachandran 1999;Dreyer et al 2010). The main reason for the lack of information on the mycorrhizal susceptibility of the root orders with different root functions may be the difficulty of distinguishing them.…”

“…canariensis is characterised by a homorrhizal root system that can develop up to three root orders (Dreyer et al 2010). An abrupt change in diameter takes place with the development of each root order (Table 7.1).…”

“…But, in the cortex, AM development may also be hampered by root anatomical features, e.g. idioblast cells that contain crystals (Brundrett and Kendrick 1990b) or aerenchyma lacunae, which clearly reduce the tissue available for colonisation (Dreyer et al 2010).…”

“…In monocotyledonous plants such as Arecaceae, other anatomical and morphological features could be proposed, e.g. the absence of aerenchyma and sclerenchymatic ring, as indicators of absorptive functions (Dreyer et al 2010).…”