We all know that the world’s population is increasing; it reached 7 billion last year. There are always more hungry mouths to feed, so we need to find a way of improving our crops to gain better ‘food security.’
All around the globe there are teams of researchers looking for ways to improve crop yields. They study soil fertility, farm equipment technology, plant architecture, disease, drought tolerance… the list goes on.
If yields can be improved, food becomes more readily available and (hopefully) access to food becomes easier. To put it another way: the higher the yield the better our ‘food security.’
Advances towards this goal can come from the least-likely sounding research…
The Test Subject: Arabidopsis
A team from the John Innes Centre in the UK has just published an intriguing paper: They have been studying a tiny plant much-loved by molecular biologists: Arabidopsis thaliana. This small flowering plant has a remarkably short lifecycle, it can take just six weeks to go from germinating seed to producing ripe seed of its own. I spent several years of my early career growing this inconspicuous yet important little plant.
Arabidopsis has one of the smallest genomes within the plant kingdom. It has just five chromosomes and around 27,000 genes. We know so much about the genome that The Arabidopsis Information Resource (TAIR) exists to collate and maintain the most current information.
During daylight, the plant produces starch through photosynthesis. The starch builds up in the leaves and is used for round-the-clock growth, repair and energy release. If it is dark and the plant runs out of starch, it will not grow as well. However, it is also true that if the plant keeps too much starch in reserve, it is wasting an opportunity to grow. It must find the right balance for optimal growth.
Plants Use Maths To Get Them Through The Night
Antonio Scialdone and his colleagues at The John Innes Centre have shown that Arabidopsis uses simple arithmetic division to manage its starch stores. The management is so effective that the reserves last almost precisely until dawn, even if ‘surprised’ by an unusually early or late night. This suggests that active management is occurring: The plant must be dividing its resources by the amount of night time still remaining.
We know that plants can measure time using their internal (circadian) clock but how do they measure their starch reserves? And how on earth do they do the calculations?
The team suggest that the process is not like a complex digital computer, it’s a simple analogue balance of chemical reactions. They showed that a very simple mathematical model could be used to explain starch management during darkness: R = S/T.
R = the rate of starch use
S = the concentration of the molecule which increases the rate of starch use
T = the concentration of the molecule which reduces starch use (by measuring the amount of time until dawn)
To test the theory, the researchers used the wonderful bank of knowledge which exists about Arabidopsis. They repeated the experiments in plants which lacked critical enzymes from starch break-down, finding that the calculation step might be down to an enzyme called phosphoglucan water dikinase or PWD for short.