Rapid Cycling Brassicas

Rapid Cycling Brassica Investigations

Jeffery Gray

Abstract:

Rapid-cycling brassicas has been used by researchers because of traits that make it convenient to study such as: short life cycle, rapid flowering time and seed maturation, small size, and ability to grow under 24 hour fluorescent

light, etc... These traits make RCBr's valuable laboratory models for students to study inheritance and selection along with evolution. Trichome/hairs on plants are extremely variable in their presence across species, location on plant organs, density, and therefore functionality The investigation conducted supports the hypothesis that trichrome number is a heritable trait that can be artificially selected for by breeding two select populations of RCBr's with one another.

introduction

Rapid-cycling populations of important species in the genus Brassica have unusual potential for resolving many problems in plant biology and for use in education. Rapid-cycling Brassicas can produce up to ten generations of seed per year and serve as models for research in genetics, host-parasite relation, molecular biology, cell biology, plant biochemistry, population biology, and plant breeding. Brassicas are a highly diverse group of crop plants that have great economic values vegetables and as sources of condiment mustard, edible and industrial oil, animal fodder, and green manure. These plants can also be used in the classroom as convenient, rapidly responding, living plant materials for 'hands on' learning at all levels of our educational system. Trichome/hairs on plants are extremely variable in their presence across species, location on plant organs, density, and therefore functionality. However, several basic functions or advantages of having surface hairs can be listed. It is likely that in many cases, hairs interfere with the feeding of at least some small herbivores and, depending on stiffness and irritability to the predator, large herbivores as well. Hairs on plants growing in areas subject to frost keep the frost away from the living surface cells. In windy locations, hairs break up the flow of air across the plant surface, reducing evaporation. Dense coatings of hairs reflect solar radiation protecting the more delicate tissues underneath in hot, dry, open habitats. And in locations where much of the available moisture comes from cloud drip, hairs appear to enhance this process. Cross pollinating rapid cycling brassicas containing 11-15 trichomes with plants containing 16-20 and 21-25 Trichome will produce significantly more offspring with more than 15 Trichome visible on their first true leaves.

materials and methods

protocol: The first lab, session six containers of three Rapid cycling brassicas (RCBr's) each were planted, three fertilizer pellets were added to each container(14,14,14), and the containers were watered by a passive watering/ wick system. Day 7: two or three seedlings were observed in each container approximately two and a half inches tall. All except one seedling was kept in each container and the others were cut out. Day 28: Group data was compiled by counting the numbers of Trichome on the first true leafs of each RCBr left. Day 35: Plants were pollinated with bee sticks, five 11-15 trichrome plants were cross pollinated with one 16-20 trichrome plant and with one 21-25 trichrome plant. Day 49: twenty days after the last pollination, plants were removed from the watering system and allowed to dry for five days. The seeds were then harvested by gently rolling dry seed pods between a pair of hands over a