RESEARCH
Plants need to assimilate CO2 for photosynthesis and, at the same time, prevent excessive loss of water. Therefore, land plants have developed stomata, which regulate the exchange of gases
between the atmosphere and the interior of the leaf. Each stomatal pore is mediated by two guard
cells that increase and decrease in size, thereby controlling the rate of transpiration and the
diffusion of CO2. Over 95% of plant water is lost through stomatal pores. For this reason, the
opening and closing of the stomata are tightly regulated by physiological and environmental
factors.
Our world is going through dramatic climate change, which forecasts water scarcity, elevated
world temperatures, extreme colds, and a dramatic increase in atmospheric CO2. Stomatal
conductance is mediated by these environmental factors, which dramatically affect crop plant
physiology, viability, growth, productivity, and eventually yield.
In our lab, we use physiological, biochemical, histological, and molecular tools to study the
different aspects of climate change on plant transpiration regulation. Our research focuses on
exploring mechanisms and pathways that are involved in stomatal conductance regulation in response to CO2, drought, and cold stress. We combine applied and basic science to advance
knowledge and provide practices for agricultural problems.
PROJECTS
Almond trees in the face of climate change
​A basic and applied study aims to incorporate beneficial traits from native almond species to cope with various effects of climate change
Dr. Tamar Azoulay-Shemer’s current research continues the long-standing tradition of almond
variety improvement at the Newe Ya'ar Research Center, where efforts to enhance almond
cultivars have been ongoing for decades. Her team focuses on the development of advanced
almond hybrids through molecular breeding techniques and field trials. A key aspect of this
research is the integration of valuable traits that were lost during the domestication of
commercial almond varieties, such as resilience to environmental stress, pests, and diseases
resistance, and improved fruit characteristics.
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Leading the Israeli Almond breeding program, Dr. Azoulay-Shemer’s team is working to
incorporate additional traits into almond hybrids that will enhance their resilience to biotic and
abiotic stresses. This includes pest and disease resistance—such as to the almond wasp and the
bacterial pathogen Xylella fastidiosa—and improved physiological traits. The aim is to
genetically characterize resistance traits, using molecular markers, and develop new hybrids that
can thrive under the challenges posed by climate change.
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Moreover, her research highlights the unique physiological trait of stem photosynthesis
capability (SPC) found in the wild almond species Prunus arabica. Our findings indicate that
SPC provides the ability to perform photosynthesis year-round via the tree stems, even during the
winter, after leaf fall. This trait is characterized by delayed bark formation, chlorophyll-rich
palisade-like parenchyma, functional stomata, and a specialized vascular system. Our studies
focus on identifying the physiological and their genetic components of the SPC, with the goal of
integrating them into commercial almond cultivars. Offering a promising avenue for developing
resilient, high-yielding plants adapted to climate challenges.​​
Chilling Damage in Mango Trees: A Pioneering Research Project
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Dr. Tamar Azoulay-Shemer's lab is conducting groundbreaking research on chilling damage in
mango trees, addressing a critical challenge in tropical and subtropical fruit production. Mango,
the second most important tropical fruit crop globally, is particularly vulnerable to cold stress,
especially in Mediterranean climates. The research focuses on "night-cold-day-light" stress, a common phenomenon in temperate mango-growing regions where nighttime temperature drops are followed by warm, bright days. This type of stress can significantly impact tree physiology and yield. The project combines physiological and molecular analyses to understand the mechanisms of cold stress response in mango trees. By integrating basic and applied research approaches, Dr. Azoulay-Shemer's team aims to develop effective, economical treatments to mitigate cold stress injury.
This work is crucial for the mango industry, which currently lacks cost-effective solutions to combat chilling damage, and has broader implications for adapting tropical fruit production to the challenges posed by climate change and increasing weather extremes.
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CO2 Stomatal conductance regulation
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Stomatal pores are responsible for plant water loss. CO2 levels in leaves are determined by respiration, photosynthesis, stomatal conductance and atmospheric [CO2]. Low concentrations of CO2 cause stomatal opening, whereas elevated CO2 concentrations trigger stomatal closure. It has been suggested that plant hormones are involved in stomatal conductance regulation. Our aim is to detect plant hormones that are involved in CO2-induced stomatal movement. We study this complex mechanism using reverse genetics, physiological, metabolomics, and biochemical approaches.
