How Plans Fight Diseases

Scientists have shed new light on how plants fight diseases caused by bacterial pathogens.  Plants are like all other living things in that they are susceptible to disease. Generally this type of plant is quite hearty when cared for properly and is only typically susceptible to a couple of different types of diseases. If you know what the diseases are and what to look for, you can usually catch the disease early on so it can be treated as quickly as possible. The more quickly the rubber plants disease is treated the less likely it is to affect the plant long term.

Oedema is one type of rubber plants disease.  This is a disease that comes about when the roots of the plant soak up water faster than the water can be used by the plant.  What happens is that the root structures fill with water and the water pressure builds up in the cells of the leaf, which causes the leaves to look blistered.   

Oedema will often look like blisters on the plant.  They may start out the same color as the rest of the plant but then change to a more hardened form and turn white, tan or brown and even take on an almost wart like appearance.  Usually if the problem is not treated the leaves will begin to drop off the plant, the plant will begin to look weak, and then it will stop growing all together.  This disease is almost always seen in the later parts of the winter, but may also occur when the soil the plants are in is warm and wet and the air is cool and moist as well. 

"Some scientists have shown that these proteins block signaling transduction pathways in the plant, which eventually weakens plant immunity. We are introducing a fresh perspective on this topic, namely, that the pathogens evolved strategies to directly attack the production of plant antimicrobial compounds, such as isoflavones, thus compromising the plant''s defense mechanism," said Ma.

Once affected it can be hard to reverse the effects of Oedema.  To avoid it, the plants should be kept in places where the relative humidity is below 70% during the winter months.  Plants should be spaced further apart if this is a continuing problem to allow for more air flow.  Most plants may suffer during the winter months but then recover in the spring and summer months due to better water absorption. 

Rubber plants are also susceptible to powdery mildews.  Some plants are able to withstand the mildew but the weaker ones may actually stop growing and even begin to die.  The mildew usually appears on the plant as a gray or white power that coats some or all of the parts of the plant.  The spots often start out as small spots that will eventually overtake most, if not all, of the surface of the plant.

First, the pathogens inject virulence bacterial proteins, called HopZ1, through needle-like conduits into the plant cells. These proteins then largely reduce the production of the isoflavones and promote disease development.

However, by sensing the presence of HopZ1, the plants mount a robust resistance against the pathogen, including the production of a very high amount of isoflavones. At this point, the pathogen must come up with new strategies by either changing the kind of proteins it injects into the plant, not injecting any proteins at all, or injecting virulence proteins in a way that helps them escape detection by the plant. In this way, the virulence bacterial proteins and the plant host engage in an endless "arms race."