Abstract Detail

Pollination Biology

Cota-Sanchez, J. Hugo [1], Almeida, Odair [2].

Systematic implications of nectary types and nectar concentration in epiphytic cacti of tribes Hylocereeae and Rhipsalideae (Cactaceae).

Plant reproductive traits provide valuable systematic information. Despite the ample diversity of reproductive systems and evolution of floral sexual dimorphism in the Cactaceae, the reproductive biology of this family has been investigated in less than 10% of its species. Similarly, the taxonomic value of architectural design and organization of internal floral parts has remained virtually unexplored in the family in spite of the striking floral shapes. The occurrence, position, characteristics, and types of floral nectaries are sources of valuable morpho-anatomical comparative data to infer phylogenetic relationships. This information assists in explaining aspects of pollination biology and reproductive mechanisms in plants, and leads to robust phylogenies. Also, floral nectaries provide insights in relation to reproductive trends because nectaries have different origins and play a vital role in pollination, usually enhancing output in reproductive success and seed set. This study provides an extensive survey on flower and nectary morphology in the cactus family focusing on tribes Hylocereeae and Rhipsalideae (subfamily Cactoideae). The objectives were: 1) to conduct comparative morphological analyses of flower and floral nectaries and 2) to compare nectar solute concentration in these two tribes consisting of holo- and semi-epiphytic species. A wide array of floral features, nectaries and nectar sugar concentration were investigated in 25 taxa of tribes Hylocereeae and Rhipsalideae. Our results demonstrate that flower morphology, nectary types, and sugar concentration of nectar have strong taxonomic implications at the tribal, generic and specific levels. Foremost, three types of nectaries were found, namely chamber nectary (with the open and diffuse subtypes), furrow nectary (including the subtype nectar holder), and annular nectary. All Hylocereeae species possess chamber nectary, in which the nectarial tissue has both trichomes and stomata as nectar-secreting structures. The Rhipsalideae is distinguished by two kinds of floral nectaries: furrow and annular, both nectary types with stomata only. The genus Rhipsalis is characterized by the annular nectary type. Nectar concentration is another significant taxonomic indicator separating the Hylocereeae and Rhipsalideae. There is an inverse relationship between flower size and amount of nectar production in the smaller Rhipsalideae flowers, in which nectar concentration is more than two-fold higher despite the smaller volume of nectar produced when compared to the large nectar volume and flower size of the Hylocereeae. In conclusion, floral attributes, nectary type and nectar sugar concentration provide reliable characters to delimit taxonomic boundaries at different levels in the Hylocereeae and Rhipsalideae.

1 - University Of Saskatchewan, Department Of Biology, 112 Science Place, Saskatoon, SK - Canada, S7N 5E2, Canada
2 - Universidade Estadual De Maringá, Insituto De Biociências - Botany / Plant Anatomy, Av. Colombo 5790, Maringá, N/A, 87020-900, Brazil

Keywords:
Cactaceae
floral nectaries
nectar
Hylocereeae
Rhipsalideae
pollination.

Presentation Type: Oral Paper:Papers for Topics
Session: 40
Location: Firs South/Boise Centre
Date: Wednesday, July 30th, 2014
Time: 1:30 PM
Number: 40001
Abstract ID:675
Candidate for Awards:None