Matter of Selection

I have observed that the shape  of the leaves seems to be the most different throughout the Brassica Oleracea plants. There appears to be four different leaf styles, bumpy, frilly, oval and long and skinny. Out of color, stem build and height, leave shape has proven to show the most variety, most of the colors are green or purple, stems are mostly thick with branches, and the plant heights all range from 1 foot to 3 feet.  

FRILLY

BUMPY

OVAL

FRILLY

LONG AND SKINNY

I believe the reason for this variety is natural variations. Each plant serves its own purpose and has to survive its own way. So they have they will each have their own structure that allows them to do so. For example, all the plants hold water and protect themselves differently, so the veins and structure of their veins are different. Other factors such as environment and sun exposure may affect things like the height of a plant. plants that rehire a lot of sun will grow taller than those shorter plants shaded by over things. 

Throughout all the plants, the color of dark green stays eminent. Every plant has at least a little bit of dark green somewhere. Most appear on the stems if not on the leaves, for example, cauliflower and broccoli which have flowers instead of leaves, have dark green stems. Others types of broccoli and kohlrabi have purple stems and green leaves.

Selective breeders could create variety through the environment in which the plants must survive. If the plants were all put in an environment alien to all the plants, then they would create the same adaptations. For example, if one were to put all the plants into an environment with a lot of shade, the plants may grow taller so they can reach the sunlight, dew and rain water.