Rapa Intraspecific Competition

traspecific competition in growth of Brassica rapa in low and high-density treatments

Rimel, Stuart F

(thursday 11am)

Abstract Intraspecific competition was examined on Brassica rapa, a species of fast growing mustard. Intraspecific competition is competition between individuals of same species living in the same population and competing for a limiting resource (Aspbury and Gabor, 2007). Brassica rapa was grown in a Laboratory in 10.16 cm pots and grouped in treatments of low density – 2 seeds to one pot, and high density- 10 seeds to one pot, and measurements were taken over a seven week period. Data collected from the experiment indicate that intraspecific competition affects developmental characteristics of B. rapa.

Introduction
Brassica rapa, a variety of mustard, completes its life cycle within six weeks and makes for an exceptional organism for observation on the effects of intraspecific competition due to B. rapa’s speedy life cycle (Aspbury and Gabor, 2007). Experimentation and observation of intraspecific competition may provide insight to the leading explanation for the developmental characteristics of individuals of a given species grown within high-density populations (Ungar, 1992). Developmental changes in; proportion of surviving individuals, forage biomass, plant height, number of seeds per individual, mean biomass of seeds per individual, number of seeds per pod, and mean root biomass will be observed among B. rapa low density populations against B. rapa high density populations to determine the density-dependent characteristics between both treatments. This study sets out to examine and analyze how intraspecific competition affects developmental changes and modifications to Brassica rapa populations grown in low and high-density
The experiment was composed of two treatments: the low-density treatment was composed of two Brassica rapa seeds in a 10.16cm pot while the high-density treatment was set at ten B. rapa seeds in a 10.16cm pot. During the first week, 10.16 cm pots were filled with soil and 6 fertilizer balls, and Brassica rapa were sown; 2 in the designated low density pot and 10 in the high density pot. Both treatments of B. rapa were placed in a plastic box with gravel and water at the bottom 6-8 centimeters from light source. During the second week, the number of plants germinated from week 1 was counted, and the frequency of survivors was calculated by dividing the number of plants in each pot by the initial number of seeds sown. During the third week, the total number of plants in each pot was counted and the frequency of survivors was recorded. During the fourth week, the total number of plants in each pot was counted along with the total number of flowers in each pot. The flower density was calculated by dividing the total number of flowers in each pot by the number of plants in their respective pot. Pollination was preformed with a cotton-tipped applicator stick within each treatment separately. Note that pollination was only performed within each treatment, take care not to cross-pollinate between low and high-density treatments. Pollination was continued into week five.