Clock is ticking for better stomatal control


One of the things that I find really frustrating about academia (and a significant part of why I enjoy teaching so much) is how narrow your focus has to become. I have lots of biological interests: I find stress biology incredibly interesting. I am fascinated by epidemiology. I did an internship looking at sexual systems in plants. As a scientific researcher though, most of that gets shut down. If there isn’t a viable possibility for collaboration then you may as well forget it. Time spent reading about neurology or viral resistance is apparently time wasted for me.

Thankfully, I have a blog, and today – having given blood this morning – I am in no shape for lab work. If I were sensible I would be reading or writing or being otherwise productive. But, using the excuse that I would probably accidentally delete my entire Methods section (give me some credit, I faceplanted the floor of the donation room twice) I am reading about other interesting science.

As an undergrad, one of my favourite modules in second year was Animal Physiology. Truth be told, had advanced neurology not been a compulsory third year option for Animal majors I could very well have specialised in Animals, not Plants. The module covered lots of interesting bits: hibernation and torpor; diving physiology and circadian rhythms. Your circadian rhythm is responsible for telling your body what time of day it is. It’s why you wake up in the morning even if you’re still tired, why you get hungry at certain times of day even if you’ve eaten recently and why you metabolise alcohol at different rates depending on the time of day.*

It’s not just animals that have circadian rhythms either: plants have an internal clock that means that even on an overcast day flowers ‘know’ to open and stomata allow transpiration. A group at Dartmouth headed by Rob McClung sees understanding these internal clocks as key to preparing our crops for the future. A significant number of the aquaporin proteins that control stomatal opening are controlled by circadian rhythms: understanding them could be vital to optimising the ongoing battle to balance water loss and photosynthesis.

In order to photosynthesise, plants need a consistent source of carbon dioxide. This enters through the stomal pores (or stomata) in the leaves. Unfortunately, this also allows water vapour to escape, meaning that the plant must absorb more through its roots. On a hot day this can work to cool the plant down, but usually this represents inefficient water usage. Given that the world already has a chronic shortage of freshwater (and irrigating dry land often leads to salinisation and heavy metal contamination) poor water use efficiency in crops can be catastrophic for productivity.

The group at Dartmouth has a multi-million dollar grant, with which they have been mapping both Water Use Efficiency genes and circadian rhythm genes in Arabidopsis and brassicas and found that the two often occur in the same areas. Though they don’t yet have a long term plan for how this information could be agriculturally useful, the potential to control water use efficiency through circadian rhythm genes is very exciting.

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Edwards, C.E. et al (2012) Quantitative Variation in Water-Use Efficiency across Water Regimes and Its Relationship with Circadian, Vegetative, Reproductive, and Leaf Gas-Exchange Traits
Mol. Plant 5 (3): 653-668. doi: 10.1093/mp/sss004

Salsano, Maly and Sasse (1990) The circadian rhythm of intra-acinar profiles of alcohol dehydrogenase activity in rat liver: a microquantitative study
The Histochemical Journal 22 (8): 395-400

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