Diurnal High Temperatures Affect the Physiological Performance and Fruit Quality of Highbush Blueberry (Vaccinium corymbosum L.) cv. Legacy.

In this study, the physiological performance and fruit quality responses of the highbush blueberry (Vaccinium corymbosum) cultivar Legacy to high temperatures (HTs) were evaluated in a field experiment. Three-year-old V. corymbosum plants were exposed to two temperature treatments between fruit load set and harvest during the 2022/2023 season: (i) ambient temperature (AT) and (ii) high temperature (HT) (5 °C ± 1 °C above ambient temperature). A chamber covered with transparent polyethylene (100 µm thick) was used to apply the HT treatment. In our study, the diurnal temperature was maintained with a difference of 5.03 °C ± 0.12 °C between the AT and HT treatments. Our findings indicated that HT significantly decreased CO2 assimilation (Pn) by 45% and stomatal conductance (gs) by 35.2% compared to the AT treatment. By contrast, the intercellular CO2 concentration (Ci) showed higher levels (about 6%) in HT plants than in AT plants. Fruit quality analyses revealed that the fruit weight and equatorial diameter decreased by 39% and 13%, respectively, in the HT treatment compared to the AT treatment. By contrast, the firmness and total soluble solids (TSS) were higher in the HT treatment than in the AT treatment. Meanwhile, the titratable acidity showed no changes between temperature treatments. In our study, Pn reduction could be associated with stomatal and non-stomatal limitations under HT treatment. Although these findings improve our understanding of the impact of HTs on fruit growth and quality in V. corymbosum, further biochemical and molecular studies are need.

From epidermal cells to functional pores: Understanding stomatal development.

Stomata, small hydromechanical valves in the leaf epidermis, are fundamental in regulating gas exchange and water loss between plants and the environment. Stomatal development involves a series of coordinated events ranging from the initial cell division that determines the meristemoid mother cells to forming specialized structures such as guard cells. These events are orchestrated by the transcription factors SPEECHLESS, FAMA, and MUTE through signaling networks. The role of plant hormones (e.g., abscisic acid, jasmonic acid, and brassinosteroids) in regulating stomatal development has been elucidated through these signaling cascades. In addition, environmental factors, such as light availability and CO2 concentration, also regulate the density and distribution of stomata in leaves, ultimately affecting overall water use efficiency. In this review, we highlight the mechanisms underlying stomatal development, connecting key signaling processes that activate or inhibit cell differentiation responsible for forming guard cells in the leaf epidermis. The factors responsible for integrating transcription factors, hormonal responses, and the influence of climatic factors on the signaling network that leads to stomatal development in plants are further discussed. Understanding the intricate connections between these factors, including the metabolic regulation of plant development, may enable us to maximize plant productivity under specific environmental conditions in changing climate scenarios.

Dynamic shifts in primary metabolism across fruit development stages in Capsicum chinense (cv. Habanero).

The development of fleshy fruits involves changes in size and mass, followed by cell differentiation, which is associated with anatomical and histological changes. Parallel to these changes, metabolic alterations lead to the production of osmolytes and energy that modify cell turgor pressure, thereby promoting cell expansion and fruit growth. Detailed information is known about these processes in climacteric fruits (e.g. tomato); however, the regulation of metabolism and its association with anatomical changes in non-climacteric fruit development are poorly understood. In this study, we used detailed anatomical and histological analyses to define three developmental phases of chili pepper (Capsicum chinense cv. Habanero): cell division, cell expansion, and ripening. We showed that each was marked by distinct metabolic profiles, underpinning the switches in energy metabolism to support cellular processes. Interestingly, mitochondrial activity was high in the early stages of development and declined over time, with a modest increase in O2 consumption by pericarp tissues at the beginning of the ripening stage. This respiratory-like burst was associated with the degradation of starch and malate, which are the sources of energy and carbon required for other processes associated with fruit maturation.