Gibberellin is a plant growth regulator.

a. Outline the role of gibberellin in the germination of seeds such as those of wheat and barley. 

In an investigation of the effects of gibberellin, plants of short-stemmed and long-stemmed varieties of five cultivated species were grown from seed. The young plants of each species were divided into two groups. One group of plants was sprayed with a solution of gibberellin each day. A control group was sprayed with the same volume of water. After eight weeks, the stem length of each plant was measured and means calculated for each group of plants. A statistical test was carried out to determine whether the difference between the treatments for each species was significant.

The results are shown in the figure. The p value for each species is given.

b. Using the information in the figure, describe the effect of adding gibberellin solution to the two varieties of the five species.

c. Explain why the short-stemmed variety of pea showed a more significant growth in height when treated with gibberellin than the long-stemmed variety.

d. Suggest the advantages of cultivating crops of short-stemmed varieties of peas and beans rather than long-stemmed varieties.

Transcribed Image Text:

Short-stemmed varieties Long-stemmed varieties 1600 ns ns 1400 1400 Key |+gibberellin <0.01 ns 1200 - 1200 O control ns 1000 1000 <0.01 800 800 <0.01 600 600 ns ns 400 <0.05 400 200 200 French broad pea tomato French broad pea tomato runner runner bean bean bean bean bean bean Species Species (ns = not significant)