Flowering Phenology: An Activity to Introduce Human & Environmental Effects on Plant Reproduction
Neil, Kaesha, The American Biology Teacher
Global and local climate change has become an important topic in the last few years. Concerns regarding the impact of climate changes on ecosystems in general, resources used by humans (e.g., water, energy, crops), and the intensity and frequency of natural disasters are driving the interest. Phenology is one way researchers are studying historic and current climate changes and repercussions (Hepper, 2003; Menzel et al., 2006; Neil & Wu, 2006; Primack et al., 2004). Phenology is the timing of biological events (i.e., growth and reproduction) influenced by environmental conditions. Genes and their interactions with the environment determine the timing and duration of these events. The gene-environment interactions allow flexibility in spatially- and temporally-variable environments; however, if synchronization with food or pollinator availability is disrupted, decreased fitness (i.e., number of reproductively-successful offspring) may result. Temperature, moisture, and photoperiod are three important triggers for phenological events for both animals and plants. This lesson involves an activity to introduce the concept of flowering phenology and synchrony with pollinators and an optional, but highly recommended, lab. The lesson provides an opportunity to teach (1) what is flowering phenology (2) the interrelationships between climate, community dynamics, and plant fitness (especially pollinators), and (3) how local climate conditions may be changing (due to urbanization and global climate changes) and the influence of those changes on local flora and fauna. The level of difficulty of the material is easily adjusted to suit the requirements of upper middle school, high school, and introductory college courses.
Flowering phenology is an easy biological indicator to focus on in any biology class because:
* flowering plants are abundant in both urban centers and rural areas
* plants do not move around or run away when you get close to them
* the flowers can usually be seen any time during the day
* the same perennial individuals can be tracked over many years, providing an extensive data set to analyze
* flowering phenology provides a segue into numerous topics. Companion topics include population and community dynamics, population genetics, patchy resources in landscapes, urbanization effects, residential and public landscaping, home gardening, and food and nonfood crops.
Provided here is some background information for the instructor to use, adjusted to suit the educational level of the students, in the discussion and lecture after the activity.
Flowering in many plants responds strongly to one trigger -temperature, photoperiod, or moisture. However, triggers are not always simple. Events that trigger flowering may occur several months to a year before one sees flowers. Moreover, multiple triggers oftentimes interact (e.g., temperature and photoperiod, moisture and temperature). Provided here is a brief summary of what is known about how plants respond to the different triggers an instructor can use in the lesson lecture. While environmental responses are well known, much about the mechanisms remain to be discovered. This presents an opportunity to remind students there is still much for science to discover about the workings of nature.
Biochemical reactions, including those involved in flower production, speed up as temperature increases. Research conducted in higher latitudes (i.e., temperate, boreal, and Mediterranean ecosystems) indicate the plants that respond to temperature increases can sense and sum temperature. Summing temperatures is how degree-days are calculated. Using degree-days instead of one set temperature allows the plant to avoid early or late flowering due to unseasonable cold or warm weather. Also, the perception of temperature interacts with the perception of photoperiod to begin the biochemical reactions of flower (and leaf) production in many plants. …