International Journal of Horticulture, 2024, Vol.14, No.6, 368-380 http://hortherbpublisher.com/index.php/ijh 375 improving crop yield (Ammar et al., 2020). Especially in arid and semi-arid regions, figs have become an important alternative crop due to their unique drought-resistant mechanisms. del Rosario Jacobo-Salcedo et al. (2024) analyzed the drought tolerance differences between fig germplasm resources (such as "Guadalupe Victoria") and the commercial variety "Black Mission" under water deficit conditions by measuring physiological and biochemical indicators such as relative water content (RWC), photosynthetic rate (PN), stomatal conductance (gs), intercellular CO2 concentration (Ci), transpiration rate (E), proline (Pro), and soluble sugar content (SSC). The study showed that "Guadalupe Victoria" maintained a higher photosynthetic rate and relative water content under drought conditions, demonstrating strong drought tolerance. This genotype accumulated more proline under drought stress, which helps regulate cell osmotic pressure and maintain cell function. Additionally, the study found that proper stomatal regulation and the accumulation of soluble sugars also play important roles in the drought tolerance of figs. The significant physiological response differences among various fig genotypes under water deficit conditions indicate that analyzing these physiological and biochemical markers can effectively identify genotypes with strong drought tolerance, providing a scientific basis for achieving sustainable fig production in water-limited environments. These findings will strongly support future breeding for drought resistance and the formulation of crop management strategies. 5.3 Chemical signaling in the mutualistic relationship between fig trees andBlastophaga psenes The fig tree (Ficus carica) and its specific pollinator Blastophaga psenes form a complex mutualistic relationship. Fig pollination relies on B. psenes, while the larvae of B. psenes feed on fig pollen (Falistocco, 2020; Proffit et al., 2020). Researchers have discovered through chemical analysis and behavioral experiments that specific ratios of volatile organic compounds (VOCs) play a critical role in this specialized interaction (Proffit et al., 2020). Proffit et al. (2020) analyzed 26 VOCs emitted by fig trees and found that only five compounds elicited electrophysiological responses in the antennae of B. psenes. These include benzyl alcohol and four monoterpenes, such as (S)-linalool and (Z)-linalool oxide. Behavioral tests indicated that B. psenes has a significant preference for a specific blend of these five compounds, and even slight changes in their proportions greatly reduce their attractiveness (Figure 4). This mimicry of chemical signals helps sustain the relationship between fig trees and wasps. The study suggests that fig trees successfully attract their specialized pollinator by adjusting the proportions of VOCs rather than their types, highlighting the importance of chemical signaling in plant-pollinator interactions. This finding provides new insights into understanding other complex plant-pollinator relationships. Figure 4 Attraction responses of Blastophaga psenes females towards different VOCs alone or in blends (Adopted from Proffit et al., 2020) Image caption: Tests were conducted in Y-tube olfactometers in which females were allowed to choose between synthetic versions of the four VOCs (alone or in a blend) and control odour. In a second set of tests, female wasps could select between a blend of the four VOCs and benzyl alcohol alone, or, a blend of the four VOCs and odour of female receptive figs. For the four VOCs detected by the pollinator, proportions of each in each odour source are indicated in the pie chart. Number of wasps tested (N), number of individuals that made a choice in parentheses, and P-values (exact binomial test) are indicated for each comparison (Adapted from Proffit et al.,2020)
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