Direct Shoot Organogenesis Lab Report

A couple of weeks ago in lab we performed Direct Shoot Organogenesis using African Violets. Where we cut the leaves from 8 healthy African Violets, and then cut squares approximately .5 to 1 cm2. Then we placed the explants with the top surface down on a variety of different medias (A-H). The medias contained different concentrations of two different Plant Growth Regulators: Cytokinin and Auxin. (Concentrations can be seen on Table 1. Pg 25a) Auxin is an important plant growth regulator (plant hormone), and it’s quite powerful so it can be active at very low concentrations. For this experiment we used a synthetic Auxin called 1-Naphthaleneacetic acid (NAA). Auxins tend to inhibit the outgrowth of axillary shoots, and tend to promote the formation of root meristems. Cytokinin is another important plant growth regulator, and along with Auxin both of these hormones are very important in plant development. We

Where the auxin: cytokinin ratio for this media wasn’t high or low, it was more a moderate ratio. Having a moderate auxin to cytokinin concentration we should expect our explants to form callus. Looking back at Figure 3 the explants in Petri Dish C did produce a small amount of callus. However, these explants also produced a few small shoots and a number of root meristems. One possible explanation for the formation of root meristems; could be even though, the Auxin: Cytokinin ratio was rather moderate. There was still a moderate concentration of auxin present in the media, and auxin is a rather powerful hormone. Which allows it to be active even at lower concentrations, initiating the formation of root meristems. Secondly, when we cut the explants and placed them in the media, the explants had first a callus formed as a wound response. Once the callus had formed in response to the wound/cut, the auxin concentration stimulated the formation of root