Impact of Drought and Flooding on Alkaloid Production in Annona crassiflora Mart

Abstract

The Brazilian Cerrado is the second largest Brazilian biome. In recent decades, a reduction in rainfall has indicated an extension of the dry season. Among the many native species of the Cerrado of the Annonaceae family and used in folk medicine, Annona crassiflora Mart. has fruits of high nutritional value and its by-products are sources of bioactive compounds, such as alkaloids. The aim of the study was to investigate how water stress impacts the production of alkaloids. The study was carried out in a nursery, and the knowledge was flood, field capacity and drought. Gas exchange, chlorophyll a fluorescence, antioxidant enzymes, total soluble sugars, starch, reducing sugars, sucrose, total alkaloids and liriodenine were analyzed. We observed that plants subjected to drought had an increase in the production of total alkaloids and liriodenine, without a reduction in photosynthetic metabolism. Plants kept under drought and flood conditions dissipated higher peroxidase activity, while catalase was higher in flooded plants. Starch showed the highest concentration in flooding plants without differing from drought plants; the lowest trehalose concentrations were found in both drought and flooding plants. The drought stimulated the synthesis of total alkaloids and liriodenine without reducing the primary metabolism, which suggests adaptation to Cerrado conditions.

Differential Tolerance of Primary Metabolism of Annona emarginata (Schltdl.) H. Rainer to Water Stress Modulates Alkaloid Production

“…In this experiment, results suggest that the reduction in A net in plants under flooding was due to damage to the photosynthetic apparatus since a significant reduction in the carboxylation efficiency of the Rubisco enzyme was observed (A net /Ci). These results differ from those observed under drought conditions, as even with lower A net and gs, plants maintained carboxylation efficiency, demonstrating greater tolerance to this condition, as demonstrated with A. crassiflora [56], which also maintained carboxylation efficiency under conditions of reduced CO 2 entry into leaves during drought stress.…”

“…Thus, drought increased the starch content in A. emarginata leaves, as reported by Matos Filho and Carvalho [75], however, not differing from flooding plants, corroborating Honório et al [56]. This carbohydrate is part of the carbon "pool" within the plant [75], and it is worth mentioning that, in photosynthetic cells, starch can be synthesized and temporarily stored in chloroplasts, which is a "transitory" starch; therefore, it can be synthesized and degraded in other sugars within a 24-hour window, influencing carbon allocation throughout the plant and thus mitigating the negative effect of stress [76][77][78].…”

“…This reduction indicates that there was a decline in the photochemical efficiency of PSII and disturbance or damage to the photosynthetic apparatus of A. emarginata, since the FV/FM ratio is an estimate of the maximum quantum efficiency of the photochemical activity of PSII when the centers of reaction are open and has even been used to evaluate other types of stress, such as salt stress [63]. The same behavior was observed for Annona crassiflora plants under flooding [56], indicating that this variable measures the intrinsic functioning of PSII, reflecting the high sensitivity of this photosystem to environmental stresses [39]. A. emarginata plants in the absence of stress showed an FV/FM ratio around 0.78, similar to several species (0.83) [64].…”

Liriodenine and Its Probable Role as an Osmolyte during Water Stress in Annona lutescens (Annonaceae)

“…Similar increases were reported in Annona species that inhabit places with water availability conditions similar to those of A. lutescens. For example, in A. purpurea [20], total alkaloids increased in the roots during the driest season, and in A. crassiflora, Marques-Honório [21] reported an increase in the total content of alkaloids and the liriodenine alkaloid in roots during water stress.…”

“…Likewise, in Catharanthus roseus L., indole alkaloids such as ajmalicine, vinblastine, and vincristine increased in concentration during drought [18,19], demonstrating that water deficiency is an essential factor in their accumulation. In several Annonaceae species, such as A. purpurea [20] and A. crassiflora [21], that inhabit areas with rainy and dry seasons, the accumulation of alkaloids is modulated by seasonality, increasing during the dry season.…”