By Divya Rajagopal
Astrobotany is the study of plants under conditions prevailing in outer space. This new research domain helps in understanding life on other planets. However, growing plants in space is not as an easy task. As with humans, we must test terrestrial organisms to understand how they adapt and respond to spaceflight. Plants are no exception. We must comprehend how they are affected by space environmental stress, not just terrestrial stressors.
Astrobotany: The approach
The crops grown so far were found to have a somewhat different taste than their terrestrial counterparts. To truly understand how spaceflight affects plant biology, we turn to molecular biology and genetics. DNA is the blueprint for biological functions. Although our DNA codes every cell in our body, it does not exhibit the same characteristics under all conditions. Genes are expressed differently in different environments, through gene regulation, epigenetics, etc. Astrobotany researchers can look at how genes are manifested differently in spaceflight using molecular biology techniques. By understanding what is happening at the molecular level, we can gain a more thorough understanding of how spaceflight affects plant biology.
Why do we need plants in space?
Organic foods are currently creating awareness, not only on Earth but also in space. Research and experiments are being conducted on growing crops beyond our planet. The International Space Station does not have cooking capabilities, so the current focus in on growing plants which fall under the categories of salads, herbs, microgreens, and small fruits. Crops are being surveyed at the Kennedy Space Center and NASA is working with middle and high school students who are helping survey varieties through the Fairchild Gardens educational program. Salad crops need to be small in size, high yielding, have a high harvest index, not require dormancy, grow from seeds, etc. NASA is also working on designing a system for root crops and tubers in microgravity.
Where will we grow our plants in space?
Plants cannot grow or survive in the vacuum of space. There is no oxygen, no defence mechanism, very little gravity, and no opportunity for nutrient uptake. Growing plants in human spaceflight, systems such as a shuttle or aboard the International Space Station, helps take care of a few of these issues right away. Firstly, human spaceflight systems provide oxygen for its inhabitants and can do so for plants as well. Secondly, spaceflight systems act as shelters that can physically shield inhabitants from solar radiation. The issues which we cannot yet protect our plants from are the effects of microgravity, ionizing radiation and intense oxidative stress.
Gravity with astrobotany
As we move away from Earth, the intensity of gravitational force changes. In space or on other planets, plants will experience microgravity, hypergravity, and everything in-between. This is important because plants sense gravity. Their response to gravity is called gravitropism and it is a critical aspect of astrobotany research.
Plant gravitropism may be more intuitive than it seems. Imagine plants as a system of roots and shoots. Roots take up water and nutrients and the shoots transport them. Roots grow down and the shoots grow up. The question is, how do plants know which way is up and which, down?
Plants must sense the influence of gravity to maximize their growth. The key to their ability to detect gravity lies in the root tips of the plant, specifically in organelles called amyloplasts. Amyloplasts contain starch and are the central player in gravity response.
Why is astrobotany so important?
A regenerative life support system will be a critical part of human spaceflight expeditions in the future. One of the primary goals of humankind with regards to extensive space travel is to sustain itself in a spacecraft. We should be able to eliminate the need for resupply by growing plants in space. Not only do we need to feed future astronauts, but also keep them mentally healthy. Astronauts report feeling grounded when viewing plants in outer space. Space agriculture is, therefore, crucial for future spaceflight.
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