Structure and function of secretory glochids and nectar composition in two Opuntioideae (Cactaceae) species

Autor(es)

de Melo Silva, Stefany Cristina ^[1] ; Machado, Silvia Rodrigues ^[1] ; Nepi, Massimo ^[2] ; Rodrigues, Tatiane Maria ^[1]

Afiliação do(s) autor(es)

^[1] Sao Paulo State Univ, UNESP, Inst Biosci, Dept Bot, BR-18618970 Botucatu, SP - Brazil

^[2] Univ Siena, Dept Life Sci, I-53100 Siena - Italy

• Tipo de documento: Artigo Científico
• Fonte: BOTANY; v. 98, n. 8, p. 425-437, AUG 2020.
• Citações Web of Science: 0

Resumo

Cactaceae exhibit highly modified spines that are considered to be extrafloral nectaries (EFNs). Despite their ecological and taxonomical relevance in this family, little is known on their structure and function. We have described the anatomy, ontogenesis, and ultrastructure of the secretory glochids in two Opuntioideae species. Young cladodes of Braslliopuntia brasiliensis (Willd.) A. Berger and Nopalea cochenfilifera (L) Salm-Dyck were processed for light and electron microscopy studies. The composition of the secretions was analyzed by high performance liquid chromatography. The secretory glochids were soft, massive, and barbed, as well as translucent. Hyaline droplets on the secretory glochid apex were collected by aggressive ants. The secretory glochids originated from the areolar meristem, beginning as small protuberances formed by protoderm and ground meristem. Mature secretory glochids consisted of a central multiseriate axis of ground cells covered by uniseriate epidermis with a continuous cuticle, and exhibited three regions: (i) dilated vascularized base with parenchyma cells exhibiting features associated to nectar secretion; (ii) elongated median region with juxtaposed fusiform non-lignified parenchyma cells; and (iii) tapered apical portion with immature fibers loosely arranged cells. The exudate was sucrose-dominant with a similar amino acid profile in both species. Our results shed light on the secretory activity of glochids in Cactaceae and their role in cactus-ant interactions. (AU)

• Processo FAPESP: 17/14891-5 - Caracterização anatômica, química e ultraestrutural de espinhos secretores em duas espécies de Cactaceae
• Beneficiário: Stefany Cristina de Melo Silva
• Modalidade de apoio: Bolsas no Brasil - Mestrado