Comparing photosynthetic differences between wild and domesticated rice


Date:
November 5, 2021
Source:
Carl R. Woese Institute for Genomic Biology, University of Illinois
at Urbana-Champaign
Summary:
In a new study, researchers compared domesticated rice to its wild
counterparts to understand the differences in their photosynthetic
capabilities. The results can help improve future rice productivity.



FULL STORY ========================================================================== Millions of people in Asia are dependent on rice as a food
source. Believed to have been domesticated as early as 6000 BCE, rice is
an important source of calories globally. In a new study, researchers
compared domesticated rice to its wild counterparts to understand the differences in their photosynthetic capabilities. The results can help
improve future rice productivity.


==========================================================================
Wild rice species Oryza rufipogon and Oryza nivara are typically
weed-like and are taller than cultivated rice Oryza sativa. While these features are helpful in the wild, since they can shade out competitors,
they are unfavorable in an agricultural setting and can lead to lower
yields. Through domestication and breeding, many rice varieties have
been selected to be short with erect leaves that have steep angles,
which allows better light distribution through the canopy. Despite these improvements, the distribution is uneven and is affected by changes in
wind and cloud cover.

"Previously, researchers primarily focused on photosynthesis in constant
high light. When you're in a field, however, plants are always in dynamic conditions and leaves are rarely in constant light due to clouds,
overlying leaves moving in the wind, and intermittent shading caused
by the movement of the sun," said Liana Acevedo-Siaca, first author of
this paper, who was a graduate student in the Long lab when this work
was conducted. "Additionally, other researchers have only looked at domesticated rice in the context of photosynthetic induction. We wanted
to compare them to their progenitors to see what has changed over time."
When the light environments change from shade to sun and back, there are several photosynthetic changes that occur in the leaves. During the switch
from low to high light, the leaves start taking up more carbon dioxide for photosynthesis, a process called photosynthetic induction. In a field,
this process occurs several times a day and since the adjustment of photosynthesis is not immediate, it lowers photosynthetic performance
over the course of a day and a growing season. Conversely, during the
switch from high to low light, the stomata -- minute openings in the
leaves through which carbon dioxide, water vapor, and oxygen move --
can close too slowly, leading to unnecessary water loss.

To compare the carbon dioxide uptake and the stomatal water loss between
wild rice and O. sativa, Acevedo-Siaca grew the plants in a screenhouse,
a greenhouse with open walls, at the International Rice Research Institute
in the Philippines. Using an infra-red gas analyzer, she controlled the
light levels to mimic some of the light fluctuations that are seen in
natural crop canopies and measured how much CO2 was taken up by the leaf.

"We saw that although the photosynthetic induction was a lot faster
in the wild rice species, the domesticated species was a lot faster at
closing its stomata, leading to less water loss," Acevedo-Siaca said. "It
is possible that since O.

rufipogon and O. nivara grow in more diverse ecosystems, there might
be more competition for light and therefore more incentive to respond
quickly to environmental changes." "We found that there were differences
in photosynthesis in fluctuating light that weren't reflected under
the constant high-light conditions used in most previous studies. Even
though the size of the study was small, we hope that our results are
indicative of larger trends," Acevedo-Siaca said. "Characterizing photosynthetic induction at different levels of the canopy will inform
future studies because, in theory, leaves that are more acclimatized to
low light conditions will respond differently than those in high light conditions." "We were interested to know whether the domestication of
rice inadvertently improved its photosynthetic efficiency. Alternatively,
if the breeding process was detrimental to particular characteristics,
maybe we can go back to wild rice and introduce those traits into
domesticated rice," said Stephen Long (BSD/CABBI/GEGC), the Ikenberry
Endowed University Chair of Crop Sciences and Plant Biology. "We are also undertaking similar work with other crops such as cowpea and soybean."
This work was done in collaboration with the C4 Rice Center at the International Rice Research Institute in Los Ban~os, Philippines. The
work was supported by the Bill and Melinda Gates Foundation, Foundation
for Food and Agriculture Research, and the UK Foreign, Commonwealth & Development Office.

========================================================================== Story Source: Materials provided by Carl_R._Woese_Institute_for_Genomic_Biology,_University of_Illinois_at_Urbana-Champaign. Original written by Ananya Sen. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Liana G. Acevedo‐Siaca, Jacqueline Dionora, Rebecca Laza,
William
Paul Quick, Stephen P. Long. Dynamics of photosynthetic
induction and relaxation within the canopy of rice and two
wild relatives. Food and Energy Security, 2021; 10 (3) DOI:
10.1002/fes3.286 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/11/211105134623.htm

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