The week ahead is promising falling temperatures and a hard frost. How will this affect the reserve’s flora?
Many of the plants that responded to the end of the summer’s drought and November’s period of warm wet weather by making rapid new growth are going to suffer. The new growth will probably die as the temperature falls below freezing.
Plants are killed by frost in one of two different ways.
Firstly, frost can freeze the water in the plant’s cells and, because water expands when it freezes, the cell walls are ruptured by the ice crystals. This is almost always lethal.
Secondly, the water in the spaces between the cells can freeze. This raises the osmotic pressure which draws water out of the cells: the cells become desiccated, freeze dried, in fact. Desiccation is also almost always lethal.
But plants are resourceful organisms and have several different ways to avoid the damage that a hard frost might cause. A plant can store sugars inside their cells, which lower the freezing point of the cell’s solution in much the same way that salt lowers the freezing point of water when you sprinkle it on your garden path.
The plant’s cells can make anti-freeze proteins and secrete them into the intercellular spaces near the cell’s walls. The proteins prevent ice forming in the intercellular solutions and protects the cell from the effects of rising osmotic pressure outside its membrane.
The cells can also make proteins inside the cell that bind to the water molecules and alter the structure of the liquids inside the cell. This stabilises the cell walls so that they are less likely to rupture under pressure from either side.
Lastly, cells can alter the lipid composition of their cells walls, adjusting their stretchiness so that they can respond to falling temperatures without rupturing.
So, as you walk through the reserve’s icy landscape, think of all the chemistry going on around you as our clever flora plans to escape the worst effects of the weather.
Header image by DKG