How Trees Use Stored Nutrients to Regrow Leaves After Damage

Greg Howard
29th January, 2024

How Trees Use Stored Nutrients to Regrow Leaves After Damage

Image Source: Natural Science News, 2024

Trees, like many living things, have a way of storing food and resources to use when times get tough, such as during the chilly start of spring or after something like a pest eats their leaves. Scientists are trying to understand this storage system better, focusing on how trees manage these reserves of carbon (C) and nitrogen (N), the building blocks for growth. They're also curious about how the distance between the storage area and the place where the resources are used plays a role in all of this. In a study conducted by the University of Alberta, researchers took a close look at young aspen trees. They wanted to trace how these trees use their stored carbon and nitrogen during different times—both under normal conditions and after their leaves were eaten. By using a clever trick involving stable isotopes, molecules that are like a signature that can be tracked, they marked the nutrients in the trees. They then mixed and matched tree parts that had these marked nutrients with ones that didn't. They first looked at where the trees got their resources after their leaves started growing again in spring. What they found was that the younger leaves, closer to the stored nutrients, got the first pick of these reserves. It's like the nutrients didn't want to travel far. But as time went on, new leaves seemed to rely less on these reserves, suggesting the trees started to make their own food through photosynthesis, capturing energy from the sunlight. When the trees lost their leaves unexpectedly, and new leaves started to grow back, things got more interesting. These new leaves still got the same helping of nitrogen from the reserves as the first batch of spring leaves did, but they didn't get as much stored carbon. This means that as the trees tried to grow new leaves, they had to rely more on making food immediately from the sunlight rather than pulling from their stockpile. However, despite having plenty of starches, a form of stored energy, in the roots (about 5% of the dry weight), the trees didn't use much of this to help the leaves grow back. This resulted in the new leaves being smaller and lighter—a mere 31% of the mass of the initial leaves. This discovery hints that the aspen trees might be playing it safe, keeping their root reserves untouched just in case of future emergencies rather than using them to quickly grow their leaves back. Understanding how trees manage their resources in such scenarios is key to grasp how they grow, survive, and recover from hardships, which can be very important for forest management and conservation efforts.

BiochemEcologyPlant Science

References

Main Study

1) Tracing carbon and nitrogen reserve remobilization during spring leaf flush and growth following defoliation.

Published 28th January, 2024

https://doi.org/10.1093/treephys/tpae015


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