Biologist Rakesh Tiwari at Uppsala University's Department of Ecology and
Genetics is using an infrared greenhouse gas analyzer to measure
photosynthesis by manipulating a leaf's environmental conditions. The
portable instrument allows the researchers to measure the interaction of
light intensity, carbon dioxide concentration in the air, and temperature to
gain insights into how plants respond to the changing climate.



Rakesh, a postdoctoral researcher, shares that he and other researchers have
seen a clear degradation in the efficiency of photosynthesis in natural
tropical environments. In 2017, he participated in a research project in the
Amazon conducted by the University of Leeds to find out how rising
temperatures threaten the rainforest's ability to function. He explained
that they saw a clear pattern that trees in the Amazon are already
experiencing air temperature conditions that can affect their photosynthesis
machinery. The research team discovered that some plant species were working
at the limit of their heat tolerance. During especially hot and dry periods,
photosynthesis rates dropped to some of the lowest levels recorded in
tropical forests.



Rakesh said that the photosynthetic efficiency of a majority of Earth's
plants is down to at most 5 percent, and one of the biggest causes of this
inefficiency is photorespiration, a side reaction that occurs when the
enzyme rubisco binds oxygen instead of carbon dioxide. Another factor is the
small stomata in the plant's leaves that regulate carbon dioxide absorption
and water exchange. In extreme heat, the stomata close to save water, but
this reduces their photosynthesis rate. In some trees, stomata open at
higher temperatures to make use of evaporative cooling as a leaf-cooling
mechanism.



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