Research conducted by scientists at the University College Dublin and Nestlé’s research and development centre in Tours, France, suggests that changes in humidity levels that might be associated with climate change could have a significant effect on coffee trees.
Future climate change scenarios indicate that some coffee growing regions of the world will experience a combination of drier atmospheric conditions and higher temperatures in coming years. In addition, it is possible that parts of these ‘at risk’ areas may also be subject to more frequent, dramatic fluctuations in weather conditions, including sharp shifts in the level of atmospheric humidity.
At present, however, there is a limited amount of literature describing the effects of humidity change on coffee. This being the case, the scientists decided to investigate how Robusta coffee might react to sudden large humidity changes.
“Our first approach has been to set up a number of growth chamber experiments directed at characterizing the various effects induced by a strong ‘humidity shock on one variety of Coffea canephora (Robusta),” they told the ASIC 2014 conference.
“We have found that small Robusta plants acclimatized to high humidity (RH 99 per cent), and then transferred to a much lower humidity (RH 33-36 per cent), start to show clear leaf wilting/drooping, as well as significant reductions in leaf water content within 30 minutes after transfer.
At two hours after transfer, we observed that the leaves started to desiccate. We also have found that, as the leaves lose water, noticeable physiological changes occur, such as decreases in carbon assimilation and stomatal conductance.
On return to the high humidity conditions after two hours, many leaves were seen to recover, although they often developed spots of necrosis, indicating permanent damage had been induced by the short ‘humidity shock.’
“In parallel to measuring some of the physiological changes induced, we also have begun to measure the expression of a number of genes already known to be affected by a water deficit using quantitative RT-PCR. The first set of expression data obtained shows that several genes whose expression are induced in the leaves by lack of water in the soil, are also induced in leaves of plants subjected to humidity shock.”