The University of St Andrews

Research@StAndrews:FullText >
Biology (School of) >
Biology >
Biology Theses >

Please use this identifier to cite or link to this item:
This item has been viewed 22 times in the last year. View Statistics

Files in This Item:

File Description SizeFormat
MarizulaAraujoGranjaeBarrosPhDThesis.pdf46.29 MBAdobe PDFView/Open
Title: Studies on the pollination biology and breeding systems of some genera with sympatric species in the Brazilian cerrados
Authors: Barros, Mariluza Araujo Granja e.
Supervisors: Gibbs, P. E.
Issue Date: 1990
Abstract: Flowering phenology, floral strategies pollinator activity and breeding system were investigated in 14 species of the cerrado vegetation in Braeflia (DF), from April 1985 to April 1986 in Tabebuia caraiba (Mart.) Bur., T. ochracea (Cham.) Standl.; Erythroxylum campestre St. Hil., E. suberosum St. Hil., E. tortuosum Mart.; Diplueodon crulsianue Pohl., D. oblongus Pohl., D. ramosissimus Pohl., D. roomarinifolius St. Hil., D. villosus Pohl.; Kielneyera abdita Saddi, K. coriacea Mart., K. speciosa St. Hil. and K. variabilis Mart. The species occur sympatrically, often only a few meters apart, and conspecifics frequently occur in clumps. The majority of the species flowered during the dry season (May to August) except D. oblongue, D. villosue and K. speciosa which flowered during the wet season (December to March). Most of them flowered for several months except Tabebuia (one month). The most frequent flowering pattern was the "Cornucopian"' type, except for D. crulsianue and D. Villosus which were "Steady-State" types. Most congeners flowered synchronously, except K. speciosa which showed displacement. Flowers of all species are pollen donors (Tabebuia and Erythroxylum also have nectar rewards), but each genus presents specific floral strategies; Tabebuia, Massflowering, Erythroxylum, distyly and cauliflory, Diplueodon, enantiostyly and Kielmeyera, andromonoecy. Flowers were visited by a large spectrum of bees (38spp. ) and Erythroxylum were also visited by wasps (16 app. ). However, each genus had particular pollen vectors. Tabebuia; Centris and Bombus; Erythroxylum: wasps; Diplueodon; Apia and Trigona; and Kielmeyera; Xylocopa, despite the fact that other bees occur all year round. Controlled pollination experiments (self-, intraspecific-, interspecific crosses, tests for apomixis and from untreated bagged flowers), revealed that all species have a high outcrossing level and are selfincompatible. Only E. campeatre (shrub), D. crulsianus and D. villosus (hemixyles), showed some self-compatibility. Fluorescence microscopy indicated that pollen tubes from selfing and from interspecific cross pollinations were blocked in the ovary, suggesting that the selfincompatibility barrier operates late. Only in Erythroxylum the blockage occurred in the stigma (Thrum flowers) or in the style (Pin flowers). Fruit-set number from hand-pollinations and from natural pollination were low, but the former frequently yielded a higher number of fruits than the latter. Low fruit-set was associated with lack of resources allocated by the maternal parent for fruit maturation. In addition, it seemed that, in all species, many flowers were programmed to be pollen donors only, since they dropped without any sign of ovary enlargement even if they were hand-pollinated or were frequently visited by pollinators.
Other Identifiers:
Type: Thesis
Publisher: University of St Andrews
Appears in Collections:Biology Theses

This item is protected by original copyright

Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.


DSpace Software Copyright © 2002-2012  Duraspace - Feedback
For help contact: | Copyright for this page belongs to St Andrews University Library | Terms and Conditions (Cookies)