Reproductive ecology of dioecious Siparuna (Monimiaceae) in Ecuador–a case of gall midge pollination

The reproductive ecology of the dioecious genus Siparuna , belonging to the primitive family Monimiaceae, was investigated in Ecuador. Thirteen species were studied, and species growing at high altitudes (above 500 m) were compared with species growing at lower altitudes. The genus has specialized flowers pollinated by Cecidomyiidae (Asynapta sp. and other genera) that lay eggs chiefly in male flowers since these are more easily accessible than female flowers due to their morphology. Several traits ensure that pollen transfer is accomplished: 1. long flowering of individuals and single flowers; 2. specific floral morphology (unisexuality, landing platform, restricted pore) allowing the flowers to be visited by Cecidomyiidae seeking egg-laying sites, and 3. a low number of ovules that have to be pollinated in each flower. The low number of ovules per flower results in a high pollen-ovule (P/O) ratio even though pollen production in male flowers is only moderate.
High altitude species had larger flowers, higher pollen-ovule ratios, fewer ovules per female flower, and longer periods of anthesis. Gender differences were seen in the longer functionality of female flowers; the larger numbers of male flowers produced; and the average diameter at breast height (DBH) biased for one of the two sexes depending on the species investigated, with no clear trend in the size distributions of individuals of both sexes. Sex ratios departed significantly from unity both to male and female bias but usually were in favour of males. There were no general differences in the ratio of functional male to female flowers at the time of observation nor in the sizes of male and female flowers. The evolution of unisexual flowers in Siparuna can be explained as a result of the differential predation by larvae: unimportant in male flowers, destructive if occurring in female flowers.     

A rapid procedure for the construction of PCR cDNA libraries from small amounts of plant tissue

We describe a general method for the preparation of λZAP II cDNA libraries from very small amounts (<50 mg) of plant tissue. We have achieved this by combining an efficient method for RNA extraction with a modified PCR protocol for the synthesis and amplification of cDNA. Using this protocol we have found it possible to generate cDNA libraries containing more than 10⁶ clones from as little as 1 μg of total RNA.     

SPATIAL FLOWER PARAMETERS AND INSECT SPATIAL VISION

The present article reviews recent and older literature on the spatial parameters that flowers display, as well as on the capacities of anthophilous insects to perceive and use these parameters for optimizing their foraging success. Although co-evolution of plants and pollinators has frequently been discussed with respect to floral colours and insect colour vision, it has rarely been assessed with respect to insect spatial vision and spatial floral cues, such as shape, pattern, size, contrast, symmetry, spatial frequency, contour density and orientation of contours. This review is an attempt to fill this gap. From experimental findings and observations on both flowers and insects, we arrive at the conclusion that all of the spatial and spatio-temporal parameters that flowers offer are relevant to the foraging task and are tuned to the insect's visual capacities and visually guided behaviour. We try, in addition, to indicate that temporal cues are closely related to spatial cues, and must therefore be included when flower–pollinator interactions are examined. We include results that show that colour vision and spatial vision have diverged over the course of evolution, particularly regarding the processing of spatio-temporal information, but that colour vision plays a role in the processing of spatial cues that are independent of temporal parameters. By presenting this review we hope to contribute to closer collaboration among scientists working in the vast fields of botany, ecology, evolution, ethology and sensory physiology.     

Oxypetalum banksii subsp. banksii: a taxon of Asclepiadaceae with an extragynoecial compitum

 The floral morphology of seven Oxypetalum species and, in particular, the spatial relationship between the five stigmatic chambers and two separate ovaries of their flowers with respect to transmission of the pollen tube are studied. In all species, except O. banksii subsp. banksii, floral morphology is similar to that in other Asclepiadeae, and the flowers pollinated with one pollinium develop only one follicle, which means compitum absence. In O. banksii subsp. banksii flowers, the secretory interstaminal tissue lines the inner walls of the stigmatic chambers as in the other species studied, but it also reaches the upper part of the inner surface of the filament tube, where it surrounds the styles, an unprecedented feature for Asclepiadaceae. This tissue secretes nectar and mucilage; the latter acts as transmitting medium for the growth of pollen tubes from pollinia inserted and hydrated in stigmatic chambers (“hyperstigmas”). Mucilage also functions as an extragynoecial compitum: in flowers pollinated with one pollinium both carpels develop into a follicle. Received August 28, 2001; accepted April 9, 2002 Published online: October 14, 2002 Addresses of the authors: Milene Faria Vieira (e-mail: mfvieira@mail.ufv.br), Departamento de Biologia Vegetal, Universidade Federal de Vi?osa, 36571-000, Vi?osa, Minas Gerais, Brazil. George John Shepherd, Departamento de Botanica, Instituto de Biologia, Universidade Estadual de Campinas, C.P. 6109, 13083-970, Campinas, S?o Paulo, Brazil.     

Floral biology and pollinators of three co-occurring Cistus species (Gistaceae)

BOSCH, J., 1992. Floral biology and pollinators of three co-occurring Cistus species (Cistaceae). The pollination of three species of Cistus, Cistus albidus L., Cistus salvifolius L. and Cistus monspeliensis L. is studied. Insect visitors were censused and some were captured to analyse pollen distribution on their bodies. Floral phenology, breeding systems, some aspects of floral biology (pollen and nectar production, pollen-ovule ratios) and floral morphology were also studied for each species. Flowers of C. albidus produce more pollen and nectar than the other two species studied, and attract more insects, especially those with higher nutritional requirements. All three species are highly self-incompatible, but C. salvifolius and C. monspeliensis show some features that hinder xenogamy, and they have lower pollen-ovule ratios than C. albidus. As a result, this latter species apparently receives higher levels of cross-pollination, but at the cost of a higher investment to attract and reward reliable pollinators.     

Cell division study in ‘pollen mother cells’ and ‘pollen grains’ of in vivo and ex vitro plants in Drimiopsis botryoides

The various normal and abnormal stages of meiosis and pollen mitosis of Drimiopsis botryoides are described, and a comparison between naturally propagated in vivo and tissue culture derived ex vitro plants in respect to their cytological behaviour presented. We also describe the floral morphology and investigate the relationship between the floral developmental stages and the progression of microgametogenesis. In total, 33 bivalents are observed in diakinesis, which indicate the diploid number 2n = 66 and this number is cross-checked by a haploid set of n = 33 chromosomes in pollen mitosis. Only 6.8% and 4.9% meiotic abnormalities were recorded on in vivo and ex vitro plants, respectively, which led to the formation of non-viable pollen. Finally, the microspores have to develop into tri-cellular male gametophyte. Only 0.2% pollen grains are found with a micro-nucleus. Though the higher pollen viability was recorded on both in vivo (89.3 ± 4.1%) and ex vitro (92.1 ± 4.6%) plants, but surprisingly the pollen germination rate is extremely low with 13.6 ± 1.74% and 21.3 ± 1.55%, respectively. The present study obviously enriches the cytological database of D. botryoides and may help future research on androgenesis and genetic improvement.     

Reproductive biology and pollinators in two enantiostylous Qualea species (Vochysiaceae) in the Brazilian Cerrado

• Enantiostyly is a floral polymorphism in which two floral forms in the same species differ in deflection of the stigma to right or left position. In monomorphic enantiostylous plants, flowers of the two morphs occur within the same individual, usually in the same proportion. In self‐compatible species the function of monomorphic enantiostyly is proposed to increase outcrossing rates and offer a reproductive advantage under pollination limitation. Enantiostylous species are usually self‐compatible and show heteranthery, with poricide anthers and pollen as pollinator reward; however, there are families, such as Vochysiaceae, that have different characteristics.
• We analysed the reproductive system and pollination biology of Qualea parviflora and Q. multiflora, two enantiostylous species from the Brazilian Cerrado that have specific morphological and physiological traits. For this, we characterized flower traits, performed hand pollinations and studied floral visitors.
• We found no differences between morphs in the proportion of flowers, nectar produced or its concentration, pollen quantity and fruit set. Both species were self‐incompatible and quite generalist regarding floral visitors.
• Enantiostyly in self‐incompatible plants seems to confer a reproductive advantage by reducing self‐interference resulting from stigma clogging. This novel result helps to expand our knowledge on this complex floral polymorphism and opens new avenues for future research on this topic.