Abstract
The success in the application of artificial pollination techniques, aspects of floral biology should receive special attention, especially regarding the viability studies of pollen grains. In this sense, two experiments were carried out, aiming to determine the floral stages: floral opening (anthesis), female, male and senescence stages of A. squamosa L flowers under tropical climate conditions, and to evaluate the germination and viability of pollen grains submitted to different storage conditions. In the first experiment, observations and data collection began when flowers were still closed. Readings were taken every two hours for 46 hours until all the flowers reached the senescence stage. For the second, the experimental design was completely randomized, in a 2 x 7 factorial scheme, with 2 storage conditions (environment at 27 ± 2°C and refrigerated at 5 ± 2°C) and 7 pollen grain conditioning times (0, 4, 8, 12, 16, 20 and 24 hours), with 4 repetitions for the analysis of pollen grain germination and 3 repetitions for the analysis of pollen grain viability, and each repetition consisted of one blade. The variables evaluated were percentage of viable and non-viable pollen grains and percentage of germinated and non-germinated pollen grains. For tropical climatic conditions, the flower anthesis (female stage) of the sugar-apple begins at 00:00 h, extending until 12:00h on the same day. The flowers of the tree reach a functionally staminate stage (male stage) from 6 a.m. the next day. Pollen grains stored at room conditions (27 ± 2°C) remain viable for up to 24 hours after collection, showing that storage in a cold environment at low temperatures (5 ± 2°C) is not necessary. Seed pollen grains have a germination percentage of 51.25% when stored under ambient conditions (27 ± 2°C) for up to 4 hours after collection.
Highlights
The sugar apple tree (Annona squamosa L.) is species is native to tropical America, to the Antilles, and can be cultivated in tropical and subtropical areas (Liu et al, 2015)
It was observed that anthesis began at 00:00h (2nd assessment day), in 53% of marked flowers, and extending until 12:00h of the same day, when 100% of flowers reached anthesis (Figure 3)
This result is similar to that obtained for flowers of araticum (Annona crassiflora Mart.), where the anthesis is gradual and begins in the early hours of the day and may extend until the early hours of the following day (Almeida-Júnior et al, 2018)
Summary
The sugar apple tree (Annona squamosa L.) is species is native to tropical America, to the Antilles, and can be cultivated in tropical and subtropical areas (Liu et al, 2015). Is one of the most important species of the genus Annona, due to the commercial value of its fruits and to the much-appreciated taste by consumers (Zucareli, Ferreira, Silvério, & Amaro, 2008). The A. squamosa L is strongly affected by climatic conditions and depending on the seasonal variations of each biome, an advance or delay in the crop cycle may occur, affecting the viability of the floral set and the quantity and quality of fruits. George and Nissen (1988) cite that high temperatures adversely affect flower bud production, suggesting that tropical conditions are not conducive to high sugar-apple yields Rodrigues et al (2016) studying different temperatures for the in vitro pollen grain germination of A. squamosa, found that the temperature of 25 ± 1°C provided the best in vitro germination, with 48.13%, and as the temperature increased, germination percentage decreased significantly. George and Nissen (1988) cite that high temperatures adversely affect flower bud production, suggesting that tropical conditions are not conducive to high sugar-apple yields
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