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rice.jpgWhat do a fungal disease of rice, dwarf plants, flowering, and beer have in common?

Answer: They all may involve the action of the plant hormone gibberellin, a.k.a. gibberellic acid (GA).

Let me explain…..

This plant hormone was first discovered by Japanese scientists working on a rice disease called bakanae caused by the fungus Gibberella fujikuroi. (And now you see how the hormone got its name.) The fungus infects rice and produces GA as a metabolic byproduct. This is too much GA for the rice, which causes the plants to grow too tall and spindly. The plants are eventually blown over by the wind and die. The fungus dines on the remains.

Many dwarf plants produce too little GA, typically because of a mutation in a gene that codes for an enzyme involved in GA biosynthesis.

Gibberellins have long been implicated in stimulating the bolting (rapid stem elongation) and flowering in rosette plants, though it’s still unclear exactly how GA’s work in different plant families (more on this at another time).

Guinness.jpgBeer? Well, stick with me here…. Malted barley is a key ingredient in most beers. Malting (starch into sugars) is the result of the spouting (germination) of the cereal grains. And GA stimulates germination in the seeds of some plant species, particularly barley.

Thus, gibberellins mediate many aspects of plant development – from seed germination to stem elongation to flowering – all of which will likely be affected by climate change. Understanding how GA’s work in plants may help us ameliorate some of the effects of such environmental changes.

How do plants adjust their development and physiology in response to environmental conditions?

Plant response to the environment can usually be divided into three consecutive steps: perception –> signal –> response.

That is, land plants must first perceive the environmental conditions. They then use hormonal signals to elicit appropriate biological responses. Some responses affected by gibberellins include: seed dormancy/germination, plant height, and flowering.

Indeed, gibberellins have been theorized to be critical in how early land plants learned to respond to changing environments.

Array.jpgHow do gibberellins work?

A fundamental step in understanding how a signal works is identifying what specifically receives the signal.

Hence, much effort has been devoted to identifying and characterizing plant hormone receptors.

Recent evidence supports the idea that GA works by triggering the elimination of proteins -called DELLA proteins – that inhibit plant growth.

It turns out that these DELLA proteins may be important for the integration of plant responses to the environment.

Last week two reports in the journal Nature further refined our knowledge of GA receptors proteins.

Bottom Line: Because gibberellins play a central role in plant responses to the environment, understanding how they work only enhances our ability to cope with problems – both ecological and agricultural – that may result from climate change.

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