Petal Attraction

This topic submitted by Bethany Fish, Katie Pekarek, Stephanie Wolfe, Mike Magee ( at 7:08 pm on 10/21/99. Additions were last made on Wednesday, May 7, 2014. Section: Cummins

Bethany Fish
Mike Magee
Stephanie Wolfe
Katie Pekarek

Petal Attraction


In the past few weeks we have been developing an accurate experiment dealing with the alluring characteristics of flowers to their different pollinators. We have created a process in which we categorize the characteristics of flowers into several distinct groups. These groups include diameter of bloom, height, odor, color, number of times visited, and type of pollinator attracted. By studying the collected data, we will attempt to answer the question of what aspects of a flower will attract pollinators. Because flowers will not reproduce without the aid of pollinators, it is important for us to understand pollinators in order to assist to the vitality of natural flower populations. We are currently observing flowers in their natural environment to investigate this process. Our observations thus far have led us to believe that color and odor have the most influence on the number of pollinators. Because of the cool temperatures during the morning and evening, we have found the best time frame for observing flowers is during the afternoon. This results in a more active process of pollination. So far our group has not collected enough data to accurately establish the type of scent, sweet or sour, the pollinators positively react to.

I. Introduction

The purpose of our lab is to determine the most appealing characteristics in flowers to both land and air pollinators. We hypothesize that tall flowers containing bright colors will attract the largest amount of these pollinators. However, we believe that odor will playa significant role to nocturnal pollination. By studying the flowers we will categorize pollinators and their floral interest to determine which species will last longer due to excessive pollination. Taking into consideration the increased rate of extinction among certain species of flowers, we hope to be able to recreate the ideal pollination characteristics of the dying species in order to prolong its life span. We think that it will be interesting to witness firsthand how flowers attract certain kinds of pollinators.

II. Relevance of Question.

Much work has been done this decade on the subject of pollination. The likely explanation is the increasing emphasis on sustaining agriculture on smaller areas of land for larger numbers of population under increasingly challenging conditions, with respect to climate and disasters - either natural or man-made.
A review of five articles provided background to prepare for our own study of this issue, that we might formulate an experimental approach to contribute to the investigation. These articles are quite diverse in their emphasis and in their perspective. Together, however, they provide a clear articulation of several relevant considerations and analysis of research regarding the mechanisms of pollination.
The first of these articles, by Lawrence D. Harder (1), examines the effects of pollen size on pollination of angiosperms (seed-producing, flowering plants) by bees (pollen-collecting or nectar-collecting) and birds. Harder uses statistical methodology to scrutinize the experimental data of many other researchers in this arena, looking at two studies, one of nine species of a particular genera of angiosperms and another using 16 genera (nine families) whose habitats are Australia and North America. From this data he contrasted plants offering an award (the pollinator gets nectar for its efforts) with buzz-pollinated varieties, examining the grooming characteristics of bees and birds with respect to their influence on the evolution of pollen size during pollen transport activity. Harder concluded that the "differences between bee foraging behavior and between bee- and bird-pollination seem not to affect the evolution of pollen size consistently."
Fernando Vega-Redondo (2) took another approach. He analyzed the effects of reward (noted above) in terms of game theory. Vega-Redondo argued that there exist two monomorphic states (where all flowers of a population either provide a reward or they do not) that are evolutionarily stable (the population thrives in their current adaptation). In the case of a relative scarcity of pollinators, and one unique monomorphic and evolutionarily stable state when the plants have a relative scarcity with respect to pollinators. His analysis requires the positing of certain assumptions based on the notion that reward (giving up nectar to the pollinator) is costly to the plant (reduces the fertility of the plant) relative to non-rewarding varieties. Vega-Redondo's study particularly looked at orchids, a family of flowers containing 80,000 species, each species of which is monomorphic with respect to reward. His conclusion notes that the single evolutionarily stable state (when pollinators are in abundance and plants in relative scarcity) is that of flowers of both reward categories coexisting, with the non-rewarding type present in smaller frequency. The relative scarcity of pollinators with respect to plants may produce either of two evolutionarily stable states, one monomorphically rewarding and the other monomorphically non-rewarding.
For SWT Batra (3), evolutionary considerations are not evaluated or alluded to. This group simply reviews "the early literature demonstrating the adequacy of pollination by local bee populations before intensive and extensive agricultural practices. Their article is far less imposing in its use of jargon and its intensity of presentation. They consider the economic value of using particular pollinators, especially the European honey bee, as a one-size fits all solution to maintaining ample pollination across the spectrum of agriculture. SWT Batra gives several examples, for instance, where the honey bee is demonstrably unsuited to perform the job adequately, whereas local bee populations, due to different pollinating abilities are more effective (i.e. blueberries, cranberries, and hothouse tomatoes require buzz-pollination, as opposed to nectar-feeding honey bees). He cites size, hairiness, quickness, fidelity, longevity, learning ability, flight range, cold tolerance, season, flower handling ability and other unnamed characteristics as contributing to the particular utility of certain bee populations over a generalized population of honey bees. To provide for a large human population, which requires extensive agriculture, SWT Batra concludes that the effective biodiversity necessary to improve the yields on existing croplands demands the introduction of the most efficient pollinators for any given crop.
Returning to an evolutionary context, John N. Owens, Tokushiro Takaso and C. John Runions (4) discuss the wind-pollination mechanism in conifers (cone-bearing trees) and the (natural) evolution of the process to improve pollination success. These men posit that the diversity in pollen, megastrobili (seed cones) and pollination mechanisms are the result of repeated climactic changes, restricting and isolating species within the taxonomy of conifers (a relatively small taxon - 550 species in 53 genera) for long periods of time. They examine the mechanisms in great detail, suggesting an evolutionary model to explain the current dispersion of those mechanisms in particular habitats. Their conclusion is that five major types of pollination mechanisms have evolved in this group of plants, varying in structure and function, but all achieving the same result - the capture and transport of pollen to the ovule (the female gametophyte of a plant). They further suggest co-evolution of pollen and ovules so that non-saccate (having no wings or sacci) pollen occurs in species that have erect ovules (to receive them more effectively), and saccate pollen occurs in species with inverted ovules (likewise suitably designed for receptiveness).
The final article, written by S. M. Carthew and R. L. Goldinggay, also places its thrust in an evolutionary context, but specifically deals with non-flying mammals as pollinators. They note that of the 40 published studies on this topic, nearly half have been conducted since 1990. As in other studies, their own work centers on three issues: regular and non-destructive visits to flowers by the animals under observation; substantial pickup of pollen and its subsequent transport to flowers of conspecific (of the same species) type; and evidence that pollination of flowers is successful, producing seed. One aspect of their study that applies directly to our own research are the morphological (flower size, shape and color) and physiological (timing of flower opening, pollen presentation and nectar secretion) floral traits as adaptations to pollination by non-flying mammals. Carthew and Goldingay concluded that the evidence of their own and other studies leans very strongly in favor of the attraction of nectar and/or pollen as the determining factor for pollination by non-flying mammals.

III. Materials and Methods

With this research providing background information, we plan to study a variety of flowers in predetermined areas on our campus. We will observe flowers during the day, as well as at night time. Each member of our group will visit their chosen location at four different times during the course of each day, observing the flower for ten five minute intervals. Our group will categorize flowers by height, intensity of color, shade of color, odor, and diameter of bloom. Collecting data during several intervals and taking into account five physical aspects of the flower, our group will be able to produce statistically sound results. To collect this date, we will create a five point scale to measure the scent of the flower. We will need rulers to measure the bloom, cameras to document the flowers that we study, and if available-night vision goggles. We will use the class to derive further develop our own questions about the subject. Using our pictures of flowers, we will propose questions to the class about the specific flowers. During the week of 10-10, we will begin our intense week long study of daily observations. Each day will be split up into four time intervals including morning, noon, afternoon, and night. The morning interval begins at 7 am and ends at 10 am, the noon period will include the 10 am-2pm time frame, the afternoon observation will cover 2pm-7pm, and the night interval will begin at 7pm and conclude at 7am. Group members can choose any time within the specified intervals to do their 50 minute observation. The week of 10-17, we will continue observations of flowers to add to our original data. Beginning the week of 10-24, we will start to bring together our analysis of the obtained data from the past two weeks. For the next two weeks we will be working on our lab packet and preparing our presentation for the class. To prepare our final project we will need to analyze our data using statview and t-test. We are going to separate our data and distribute it to small groups. We will have the small groups plug the information into the computer and then we will interpret the results and accept or reject our original hypothesis. We will finalize our report in the last week of our project.

Our Data Sheet contains the following categories: Location, interval, # of visits, pollinator, shade, intensity, height, diameter of bloom, and scent.

(1) Harder LD 1998. Pollen-size comparisons among animal-pollinated angiosperms with different pollination characteristics. Biological
Journal of the Linnean Society 64: 513-525

(2) Vega-Redondo F 1996. Pollination and reward: a game-theoretic
approach. Games and Economic Behavior 12: 127-142

(3) SWT Batra 1995. Bees and pollination in our changing environment.
Apidologie 26: 361-370

(4) Owens JN, Takaso T, Runions CJ 1999? Pollination in Conifers

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