Kale seed priming with red seaweed biostimulant
From Firenze University Press Journal: Advances in Horticultural Science
F. Lemes Ternus, Universidade Federal da Fronteira Sul, Chapecó, Santa Caterina
V. Neumann Silva, Universidade Federal da Fronteira Sul, Chapecó, Santa Caterina
P. Mendes Milanesi, Universidade Federal da Fronteira Sul, Erechiim, Rio Grande do Sul
B. Tortelli, Universidade de Passo Fundo, Passo Fundo, Rio Grande do Sul
Kale (Brassica oleracea var. acephala) is a vegetable crop belonging to the Brassicaceae plant family, originating from the European continent, with excellent adaptation to mild temperatures. However, there is a demand for this vegetable throughout the year. Considering the tropical climate conditions on several countries, studies of the tolerance to high temperatures in kale production are necessary. The use of seeds for kale seedlings production has been increasing in recent years, especially considering the increasing release of hybrid cultivars, which do not emit lateral shoots, preventing asexual propagation (Trani et al., 2015). Seedlings production is one of the most important stages for horticultural production systems, which requires highquality seeds.
A key component of the performance of crop seeds is the complex trait of seed vigour. Crop yield and resourceuse efficiency depend on successful plant establishment in the field, and it is the vigour of seeds that defines their ability to germinate and establish seedlings rapidly, uniformly and robustly across diverse environmental conditions (FinchSavage and Bassel, 2016). One procedure that can be used to improve seed quality is physiological conditioning, also known as seed priming. Seed priming is a presowing treatment that partially hydrates seeds without allowing radicle emergence. Consequently, primed seeds demonstrate rapid germination and improved germination rate and uniformity. Moreover, seed priming is often implicated in improving the stresstolerance of germinating seeds (Chen and Arora, 2013). Some examples of success using this technique are verified in the literature, as exemplified in the use of seed priming in spinach seed treatment that resulted in high germination rates, seedling emergence, growth, maturity and yield; in this research the maximum seed vigour was obtained when seeds were treated with 6% concentration of Sargassum wightii (Brown Seaweed) (Takoliya et al., 2018).
Studying physiological and biochemical mechanisms involved in heat stress tolerance in rice seeds, Hussain et al. (2016) found that the best performance and greater rice seedlings tolerance obtained from primed seeds, by different methods (hydropriming, osmopriming, redox priming, chemical priming, and hormonal priming) is associated with increased starch metabolism, high respiratory rate, lower peroxidation and increased capacity of the antioxidant defence system. In addition, other experimental results have shown that the higher germination efficiency and vigour (seedling growth) occur due to the mobilisation of reserves and the activation of genes responsible for the synthesis of vital enzymes during the priming procedure (Lal et al., 2018).
Seed priming can be performed with algae extracts or formulations (Sharma et al., 2014). Some researches demonstrated beneficial effects of seed priming with several seaweed species, for several horticultural crops, for example, tomato seeds primed with Anabaena minutissima, Ecklonia maximaand Jania adhaerens (Righini et al., 2021) and with Ulva lactuca and Padina gymnospora (SantacruzRuvalcaba et al., 2019); pepper seeds with Kappaphycus alvarezii (Ksap) and Gracilaria edulis(Dutta et al., 2019). Seaweeds are green, brown and red marine macroalgae. Extracts of brown seaweeds are widely used in horticulture crops, mainly for their plant growthpromoting effects and ameliorating effect on crop tolerance to abiotic stresses, such as salinity, extreme temperatures, nutrient deficiency and drought (Battacharyya et al., 2015). Red seaweeds (Rhodophyta) are sources of carrageenans, which are sulphated linear polysaccharides that represent major cellular constituents of this algae; Carrageenans improve plant growth by regulating various metabolic processes, such as cell division (Shukla et al., 2016). Studying the effects of extracts and isolated molecules of two species of Gracilaria (Gracilariales, Rhodophyta) on early growth of lettuce, Torres et al. (2018) found a promoting effect of the aqueous extracts in lettuce root length. Nonetheless, there is a lack of studies testing red seaweeds for seed treatment, especially in seed priming protocols. Therefore, the objective of this work was to evaluate the effect of kale seed priming with red algae biostimulant in seed performance under adequate conditions and thermal stress.
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