Inflorescence Production in Purple Loosestrife (Lythrum salicaria) Across a
Fertility Gradient
Richard Patterson
Department of Biology
Lake Superior State University
Sault Ste. Marie, Michigan
Abstract
Purple loosestrife is considered an invasive plant species, which thrives in moist
soils. It is a highly competitive plant, and can displace native vegetation, leaving
poor quality habitat for wetland animals. The purpose of this study is to
determine if purple loosestrife, if presented with an increasing amount of
fertilizer, will allocate this resource to produce higher quality inflorescences.
Purple loosestrife plants were grown in a range of complete fertilization with 0
ppm Nitrogen, 10 ppm Nitrogen, 20 ppm Nitrogen, and 30 ppm Nitrogen over a
period of six weeks. Plants were grown in 12” pots filled with play sand and set
in standing water in a randomized complete block design. After six weeks, the
plants were harvested, inflorescences were separated and dried. Dry mass and
inflorescence lengths were measured and mass per unit length was then computed.
Caloric content per gram was obtained through bomb calorimeter on the low
nitrogen level and high nitrogen level treatments. Analysis of variance showed
that fertilization increased total inflorescence length and mass. Mass per unit
length also increased, suggesting increased quality of inflorescences with
increased nutrient availability. Caloric content showed no difference between the
low and high nitrogen level treaments.