Here’s a fun “What makes you curious?” with Dr. Kieran.
As a geologist I’m usually focused on what’s under the ground, not what’s growing out of it! Since I’ve been spending more time in the garden lately, I’ve started to notice how many different plants are in my garden and all the different shapes of their leaves.
Some are very big and flat, and some are like tiny little needles. Some leaves have smooth edges, and some have got points or odd shapes. And not every leaf has a point on the end; some are round instead. And every leaf seems to be a slightly different shade of green!
We decided to ask Dr. Boyd Wright, a plant ecologist here at UNE, to answer some of our curious questions about leaves.
Q: Do different shaped leaves have different jobs?
Leaves have different shapes because different combinations of selective pressures
have made them that way. Some plants evolve in systems where herbivory (lots of plant eating animals) is high. As a result, they may develop stinging hairs on their leaves or spiny leaf tips that spike animals. Other plants may evolve in systems where access to light is difficult e.g. rain forests. Such plants often have larger leaves to optimise light interception.
Q: Are some better at absorbing light than others?
A: Yes sure. Bigger leaves are going to be able to absorb more light and therefore do more photosynthesis and create more biomass (yummy food) for the plant quicker. The colour of a leaf can also influence how much light is absorbed. Green leaves absorb efficiently, red or pink coloured leaves on new shoots don’t. New shoots don’t want to absorb much light though, as they are young and fragile and need some level of protection from the sun’s rays.
Q: Why do bugs prefer to eat the leaves for my vegetables instead of the trees?
A: Nothing likes to be eaten, plant or animal. Animals can outrun their predators, plants are stuck in one place. Most plants lineages would have been exposed to herbivory since day 1 of their evolutionary journey. This has meant that almost all plants produce what are known as secondary compounds in their leaves, roots, seeds etc. These compounds deter bugs and other herbivores. Over the years humans have largely bred out (though not entirely) these compounds from vegetable plants because they are bad for us and taste bad. Hence the insects have a field day with them. Trees in the forest have not had their secondary compounds bred out so they are still usually well-protected against insect attack.
Big thanks to Dr. Boyd for feeding our curiosity!