XVI International Botanical Congess

The genus Astragalus includes approximately 2500 species, with nearly 120 spp. growing in South America. This new taxon grows in Cochabamba, Bolivia at 3725 ms m, the plants are ca. 5 cm diam x 2 cm high. The leaflets in superficial view have prominence and previously unknown Abulks:@ it=s the structure and ultrastructural was study using LM, PL, SEM-EDXA and TEM. The leaflet=s characters are: papillous, epidermical cells, conspicuous bifurcated and simple papillac in adaxial and abaxial position, thick outer tangential epidermical cell wall, homogeneous cuticle, epicuticular waxes, adpressed trichomas, sunken stomata with a conspicuous epistomatic camera with voluminous subsidiary cells, and dorsiventral mesophyll. It is worthwhile to mention that this hemisperical Abulk@ is constituted by epidermal and subepidermical cells which are idioblasts with an ergastic substance intensely birefringent with PL. Different microtests confirms that these contain are not lipids, proteins or starch. Additionally, SEM EDXA analysis showed the absence of mineral elements in idioblasts. Presumably the substance within the idioblasts could be gums, further anatomical and chemical studies will confirm our hypothesis. All the characteristics previously cited show adaptive strategies of the new species to xeric environmental conditions.