Berry Cell Vitality in Grapevines

Berry Cell Vitality: A Crucial Aspect of Ripening

Research dating back to 2008 has revealed critical insights into the vitality of grape berries. Using fluorescein diacetate (FDA) staining, scientists have been able to map out the regions of a grape berry that are alive versus those that have undergone cell death. The FDA stain highlights living tissue in green, while dead cells remain unstained, offering a clear view of vitality within the grape.

Studies conducted by both the speaker and Krasnow et al. at UC Davis show that grapevine berries maintain cell vitality up to approximately 100 days after anthesis, the period following flower bloom. After this, vitality gradually decreases, varying by cultivar. For instance, wine grapes such as Chardonnay, Nebbiolo, and Cabernet exhibit noticeable cell death, while table grapes show little to no cell death—a peculiar observation suggesting a fundamental difference in their physiological responses.

Shrivel in Grapes: Correlation with Cell Death

One of the more intriguing findings is the correlation between cell death and berry shrivel. In cultivars like Shiraz, loss of cell vitality is linked with berry shrivel and reduced osmotic competence. This breakdown of cell membranes results in the inability of the berries to retain water, which leads to shriveling, particularly after the berries reach their maximum weight.

Interestingly, Chardonnay behaves differently. While it shows some degree of cell death, it does not exhibit shrivel. This difference highlights the complexity of physiological responses among grape varieties and emphasizes the importance of studying these mechanisms in greater detail.

New Methods for Measuring Berry Vitality

Historically, measuring berry vitality was a laborious process requiring a fluorescence microscope. However, advancements in technology led to the development of impedance spectroscopy as a more convenient method. By passing electrical currents through the berry, researchers can model the berry’s internal structure, assessing the health of cell membranes with precision. This technique not only complements traditional staining methods but also confirms that cell membrane leakage is a real phenomenon caused by decreased membrane capacitance and increased cell wall conductance.

Environmental Impacts: Temperature and Water Stress

Environmental conditions, particularly temperature and water stress, play a significant role in grape berry vitality. Through trials conducted over three seasons, researchers found that shading vines—whether through overhead shading or canopy shading—helped prevent the loss of cell vitality. When vines were shaded, the onset of shrivel was delayed, indicating that high temperatures contribute to cell death.

Additionally, water stress compounds the issue. Experiments showed that vines subjected to both elevated temperatures and water stress experienced a more significant reduction in berry vitality. When comparing irrigated and non-irrigated vines, the latter showed a 50% decrease in stomatal conductance, further indicating the critical role of water management in maintaining grape health during the ripening process.

Conclusion

Understanding the physiological processes behind berry vitality and shrivel is essential for viticulturists looking to optimize grape quality, especially in the face of climate variability. The use of innovative techniques like impedance spectroscopy and strategic shading can help mitigate the negative effects of heat and water stress on grapevines. As research continues, these insights will become invaluable for both growers and winemakers aiming to produce high-quality wines with consistency.

If you want to learn more about this topic on Infowine Premium there is the entire presentation “Late ripening cell death and shrivel in Shiraz” given by given by Steve Tyerman of the Faculty of Sciences of The University of Adelaide, Australia.