Callus And Tumor

Callus and Tumor

(in notes) – plants form callus in response to injury

TRUE – this is a protective mechanism, forming a layer to cover the injury and to prevent water loss.

But this is different from tumor formation involving agrobacterium tumefacien. In tumor formation, the cells are being hijacked to undergo uncontrolled cell division and secretes opines. Although this is another lump of cells, because of its nature, we don’t refer it as callus at all.

So when Ag. Tumefacien infect the plant cell through an open wound, will/can a callus be formed?

Yes it will for the above reason. But only those cells infected by the bacteria will become cancerous in nature

http://www.apsnet.org/education/lessonsPlantPath/CrownGall/pathbio.htm

Does the tumor have averse effects on the plant?

Crown Gall Disease

Both loss of yield and stunting of growth may occur when seedlings or young cuttings are infected in the early stages of plant growth. The lack of vigor, reduction in foliage, and water stress are associated with chronically diseased root systems. When more mature tree crops become infected, secondary growths will appear from the root systems near the trunk and the productivity of the plant is reduced since nutrients is siphoned away.

• gall tissue contains abnormally high amounts of auxin and cytokinin and have the machinery to synthesize those hormones
• this machinery is gained by the stable transfer of genes from Agrobacterium to the infected plant cells
• bacteria does not have to be present for the progession of the disease