ResumoMudas de Euterpe edulis de dois estádios de desenvolvimento (Classe A, 2 anos de idade, e Classe B, 4 anos de idade, com altura media de 16±1.3 e 49±3.3 cm, respectivamente), foram submetidas a três regimes de disponibilidade hídrica (déficit hídrico, reidratação e nova submissão ao déficit hídrico) em casa de vegetação. Avaliamos parâmetros fisiológicos e morfológicos para detectar diferenças nas respostas ao déficit hídrico. Plantas da classe B mostraram fechamento estomático mais rapidamente, 14 dias após início do regime (DAIR) em comparação às plantas da Classe A (que só responderam após 17 DAIR). No regime de reidratação, a Classe B alcançou valores de condutância estomática semelhantes ao controle mais rapidamente (14 DAIR) em comparação às plantas da classe A (25 DAIR). Quando submetidas novamente ao déficit hídrico, plantas da Classe B apresentaram condutância estomática duas vezes maior do que o controle, enquanto a Classe A apresentou valores cinco vezes inferiores ao controle. Este padrão de resposta deve-se às diferenças morfológicas entre os estádios de desenvolvimento, que refletem diferente comportamento hidrodinâmico. Além disso, a Classe B apresentou relação raíz/parte aérea sistema radicular mais balanceada (0.91±0.32) em comparação à Classe A, que apresentou apenas 0.51±0.17. Concluímos que plantas em estádio de desenvolvimento superior são mais tolerantes a ciclos de déficit hídrico recorrentes. Os resultaram apontam para o potencial de promover a rustificação de plantas de Euterpe edulis em viveiro.Palavras-chave: palmeira-juçara, estádios de desenvolvimento, déficit hídrico, reidratação, respostas ecofisiológicas e morfológicas. AbstractEuterpe edulis plants at two developmental stages (Class A, two-year-old seedlings, and Class B, fouryear-old-saplings, with a mean height of 16.0±1.3 and 49.0±3.3 cm, respectively), were subjected to three successive water availability regimes (water deficit, re-watering and subsequent water deficit after rewatering) in greenhouse conditions. We assessed physiological and morphological parameters to detect differences in the water deficit response. Saplings showed a more rapid stomata closure 14 days after the beginning of the regime (DABR) than seedlings (which only showed a response after 17 DABR). Furthermore, the stomata conductance of saplings subjected to the re-watering regime reached the same value as the controls faster (14 DABR) than that of seedlings (25 DABR). When again subjected to water deficit, saplings showed a two-fold higher stomata conductance than the control plants, whereas seedlings showed a five-fold lower value. This response pattern can be attributed to morphological differences between the developmental stages, which is reflected in different hydrodynamic behaviors. Saplings showed a more balanced root/aerial shoot ratio (0.91±0.32), whereas the ratio for seedlings was 0.51±0.17. We conclude that more developed plants are more tolerant to recurrent cycles of water deficit. The results suggest the potential to harden "jussar...

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Seedling species with different architectures, e.g., mean leaf angles, are often subjected to the same irrigation management in forest nurseries, resulting in wasted water and fertilizer and reduced seedling quality. We aimed to evaluate whether irrigation volumes applied to tree seedling species with different leaf angles affect the physiological quality in forest nurseries and, consequently, performance after potting. We submitted nine seedling species with different mean leaf angles to four daily water regimes (8, 10, 12, and 14 mm). In the nursery, the following physiological attributes were considered to assess seedling quality: leaf water potential, daily transpiration rate, SPAD value, chlorophyll a and b, anthocyanins, carotenoids, and total nutrient content. After potting, we evaluated height and stem diameter over 120 days. Leaf angle can be used as a criterion for optimizing irrigation in forest nurseries, avoiding water and fertilizer wastage, and increasing physiological seedling quality. Leaf angle measurements combined with concurrent assessments of leaf traits are helpful in further understanding the effects of leaf angle variation and water regime on seedling quality. For positive leaf angles, an irrigation volume of 8 mm is sufficient to increase physiological seedling quality. Conversely, seedlings with negative leaf angles show the opposite response, requiring the largest irrigation volume (14 mm) to increase physiological seedling quality, except when the mean leaf area is small and concentrated in the upper half of the stem, which facilitates the access of irrigation water to the substrate and thus satisfies seedling water requirements. For all species, up to 120 days after planting in pots, the effect of the irrigation volume that provides greater growth and physiological quality at the end of the nursery phase is not overcome by other irrigation volumes applied.