From heat stress to final quality: the physiology that defines the modern blueberry

Physiology and quality

From heat stress to final quality: the physiology that defines the modern blueberry today

At the International Blueberries Seminar, Amaya Atucha and Gerardo Núñez addressed how the interaction between environment, physiology and metabolism is redefining the productivity and quality of blueberries, in a scenario where the market demands increasingly firm, sweet, tasty and competitive fruit.

22/04/2026

The Centra Blue variety

The business of blueberry It entered a stage where competitiveness is built on quality. The presentations were structured around this premise. Amaya Atucha, a specialist in fruit production and professor of horticulture at the University of Wisconsin–Madison, and Gerardo NunezProfessor and researcher in berry physiology and nutrition at the University of Florida, UF/IFAS, offered a complementary perspective on the crop. While Atucha delved into how the environment conditions the physiological response of the plant and fruit, Núñez showed how water, carbon, photosynthesis, and nutrition translate into the quality attributes that guide blueberry production today.

Atucha focused on the crop's physiological response to cold and heat, while Núñez connected that physiology with the quality traits now recognized by the market: sweetness, flavor, firmness, and size. Thus, both presentations converged on the same idea: the final quality of the blueberry It is built throughout the development of the fruit and depends on how the plant interacts with its environment.

The environment redefines the physiological behavior of the crop

The physiology of blueberry It occupies a central place in the current discussion on production. In Amaya Atucha's presentation, one of the clearest messages was that the plant's response to the environment changes throughout its cycle and conditions both the crop's adaptation and its subsequent performance. In the case of cold, she explained that resistance is built up, maintained, and then lost during the winter, and that in blueberry Mechanisms such as supercooling are at work, which prevent ice formation in sensitive tissues.

More than just academic precision, this perspective helps us understand why varietal behavior requires a more nuanced physiological analysis. As Atucha pointed out, “understanding the mechanism is essential,” because only through this understanding is it possible to better evaluate varieties and their responses to different environmental conditions.

Amaya Atucha at the XL International Blueberries Seminar Chile 2026 © Blueberries Consulting

Cold, heat and adaptation: a more demanding plant

One of Atucha's most interesting contributions was distinguishing between dormancy and cold resistance, two related but not equivalent processes. This difference allows us to understand why the same variety can behave differently depending on the growing region, and why the accumulation of chilling hours alone is not always sufficient to accurately interpret varietal adaptation. The researcher explained that both processes interact and that the degree of cold resistance achieved by the buds during winter also influences bud break and the interpretation of cultivar performance.

This increased environmental demand is also reflected in the response to heat. In Gerardo Núñez's presentation, temperature emerged as a factor that directly impacts the physiological functioning of the system. When thermal conditions deviate from the optimal range, photosynthesis becomes less efficient, respiration increases, and the plant has less carbon available for growth, ripening, and fruit quality. From this perspective, the environment significantly influences the crop's ability to produce competitive fruit.

The quality of the fruit begins long before the harvest

Núñez established quality as the central focus of the current business of blueberryBased on consumer studies, he explained that the market seeks sweet, intensely flavored, firm, and good-sized fruit, and that these attributes can now be more accurately assessed using chemical, physical, and sensory variables. Sweetness is related to the ratio of soluble solids to acidity; intense flavor, to the composition of volatile compounds; and firmness and size, to thresholds that are increasingly relevant to the consumer experience and commercial competitiveness.

Atucha provided a crucial insight into how that quality begins to develop long before the harvest. He explained that the fruit of blueberryUnlike leaves, the fruit transpires very little, cools less efficiently, and has a more limited capacity to mobilize calcium into its tissues—a condition that influences firmness and heat tolerance. This physiological basis helps explain why the final quality depends on how the fruit develops and copes with the environment throughout its growth.

Amaya Atucha in the talk "Physiology of heat stress: adaptation mechanisms and management strategies in Vaccinium crops" © Blueberries Consulting

Water, carbon and metabolism: the foundations of quality

One of the strongest points of Núñez's presentation was to show that behind the quality of blueberry There are crucial physiological processes at play. Water, for example, plays a fundamental role in cell expansion and, therefore, in fruit size development. Based on trials of fruit growth and water deficit, it was shown that not all stages respond equally to water scarcity: there are times during development when water restriction has little effect, and others when it can significantly reduce fruit weight and quality.

Added to this is carbon. Núñez explained that blueberries are a system in which this resource must be managed with particular efficiency, since their leaves have relatively low photosynthetic rates compared to other fruit trees. Even young fruit participates in photosynthesis, a characteristic that directly links carbon metabolism to growth, ripening, and flavor. In more demanding thermal conditions, the plant operates with a tighter physiological margin, which impacts growth, ripening, and fruit quality.

Heat does not impact all stages of fruit development equally.

The Atucha presentation also honed our understanding of thermal damage in fruit. As explained, susceptibility to heat changes as development progresses. Earlier stages can dissipate some of the radiation more effectively, but as the fruit enters later stages of ripening, its ability to move water changes, its temperature increases, and its vulnerability to damage becomes greater.

In this process, the fruit's natural wax emerges as a particularly important component. Its presence helps reflect radiation and moderate surface temperature, while certain intermediate stages of coloration, with less protection and less water movement, can become critical points. In Atucha's words, the fruit "heats up rapidly," a condition that helps explain why heat influences the fruit's firmness, condition, and commercial quality.

Seen from Núñez's perspective, this reading also relates to the dynamics of fruit growth: not all stages have the same water demand or the same rate of cell expansion, so the impact of the environment is not distributed uniformly throughout the cycle.

Gerardo Nuñez in the talk "Physiological bases of the modern blueberry: Environment-Metabolism-Quality Interaction in high-demand systems" © Blueberries Consulting

Understanding physiology to produce a more competitive fruit

Both Atucha and Núñez, from different starting points, agreed on the same fundamental idea: the quality of the blueberry It is strengthened when the physiology of the crop is understood more deeply. In Núñez's case, this translated into a clear roadmap. If today the market values sweetness, intense flavor, firmness, and size, then the productive task involves better understanding how to manage water, carbon, and nutrition to guide the crop toward those attributes.

Atucha applied this same logic to heat management, demonstrating that tools like evaporative cooling, netting, and certain protective measures become more valuable when one first understands why the fruit heats up, how it responds physiologically, and why some stages are more sensitive than others. More than a collection of isolated techniques, both presentations reinforced a central idea: producing competitive fruit today requires a deeper understanding of the plant and connecting that understanding with real market demands.

The exhibitions by Amaya Atucha and Gerardo Núñez reinforced the quality of the blueberry It is built through physiological processes that begin long before harvest. In a market that demands firmer, tastier, and more consistent fruit, understanding how environment, water, carbon, metabolism, and fruit development interact is becoming increasingly crucial for maintaining competitiveness.