ABSTRACT. The scarcity of surface water has led to the use of underground sources as an alternative for crop irrigation by farmers in semi-arid regions. However, these water sources generally have high salinity, which prevents agricultural production. The objective of this study was to determine the effects of pre-germination treatments with plant growth regulators and bioactivators on melon seeds to attenuate salt stress caused by irrigation water during germination and seedling development. Two trials were carried out separately with the hybrids, Goldex and Grand Prix. The design was completely randomized in a 4 × 3 factorial scheme (four seed treatments and three dilutions of irrigation water). Seeds were treated with salicylic acid and gibberellic acid and the insecticide, thiamethoxam, in addition to the control. Local supply water, artesian well groundwater, and dilution of these waters at a 1:1 ratio were employed for irrigation. Fourteen days after sowing, morphological and physiological analyses were performed, and the material was collected for biochemical determination. The use of saline well water affected the initial development of melon seedlings of the Goldex and Grand Prix hybrids. Pre-germination treatment of Goldex hybrid seeds with gibberellic acid was inefficient at mitigating salt stress. However, the effects of irrigation water salinity on Grand Prix melon seeds pretreated with salicylic acid and thiamethoxam were attenuated.

RESUMO O pré-tratamento de sementes resulta em emergência de plântulas mais rápida e estande uniforme, principalmente, quando sob estresse. Sendo assim, objetivou-se avaliar a ação de reguladores vegetais como atenuantes de estresse durante a germinação e desenvolvimento inicial de plântulas de abóbora, cv. Baiana Tropical, irrigadas com água salina. Para isso, estabeleceu-se o delineamento inteiramente casualizado, em esquema fatorial 4 x 3, em quatro repetições. Os tratamentos foram constituídos de quatro tipos de água (A1 – 100% água de abastecimento; A2 – 100% efluente de piscicultura; A3 – 100% água de poço artesiano; A4 - mistura de 50% efluente de piscicultura + 50% água de poço artesiano) e três tratamentos de sementes (controle, ácidos salicílico e giberélico). As variáveis mensuradas foram germinação, primeira contagem de germinação, comprimento da parte aérea e raiz, massa seca da parte aérea e raiz, açúcares solúveis totais, aminoácidos totais e prolina. Os dados foram submetidos a análise de variância e teste de Scott-Knott. As plântulas de abóbora realizaram ajustamento osmótico em condições salinas da água A4. Além disso, o tratamento de sementes de abóbora com reguladores vegetais (ácidos giberélico e salicílico) beneficia a germinação e o desenvolvimento inicial de plântulas sob condições de estresse salino.

ABSTRACT Pretreatment of seeds results in faster emergence of seedlings and uniform stand, especially under stress. Thus, the objective was to evaluate the action of plant regulators as stress attenuators during germination and initial development of pumpkin seedlings, cv. ‘Baiana Tropical’, irrigated with saline water. For this, a completely randomized design was established, in a 4 x 3 factorial scheme, with four replications. Treatments consisted of four types of water (W1 - 100% supply water; W2 - 100% fish farming effluent; W3 - 100% artesian well water; W4 - mixture of 50% fish farming effluent + 50% artesian well water) and three seed treatments (control, salicylic acid and gibberellic acid). The variables measured were germination, first germination count, shoot and root length, shoot and root dry mass, total soluble sugars, total amino acids and proline. The data were subjected to analysis of variance and Scott-Knott test. Pumpkin seedlings performed osmotic adjustment under saline conditions of W4 water. In addition, the treatment of pumpkin seeds with plant regulators (gibberellic and salicylic acids) favors the germination and initial development of seedlings under conditions of salt stress.

RESUMO A adoção de tecnologias que permitam a atenuação de estresses ambientais, como o uso de reguladores no tratamento de sementes, é uma alternativa para cultivos em regiões com temperaturas elevadas. Objetivou-se avaliar a mitigação do estresse térmico na germinação e desenvolvimento inicial de plântulas de cenoura, por meio de reguladores de crescimento vegetal. O estudo foi dividido em três ensaios, utilizando-se temperaturas de 25, 30 e 35 °C. Empregou-se esquema fatorial 5 x 3, sendo cinco cultivares de cenoura (Alvorada, Brasília, BRS Esplanada, Tellus e Tropical) e dois produtos (Stimulate® e tiametoxam), além do controle (sementes não tratadas). Avaliaram-se as seguintes variáveis: germinação, primeira contagem de germinação, comprimento e massa seca de plântula. Quando as cultivares tiveram as sementes tratadas com os reguladores de crescimento vegetal a 25 °C, Tellus apresentou germinação 28 % superior ao controle, enquanto, a 30 °C, BRS Esplanada e Tellus apresentaram germinação duas vezes maior que o controle e expressaram melhor vigor, em detrimento da Alvorada, Brasília e Tropical. De modo geral, o tiametoxam promoveu incrementos no desenvolvimento inicial de plântulas de cenoura aos 25 e 30 °C. No entanto, a germinação das cultivares de cenoura foi interrompida a 35 °C.

ABSTRACT The adoption of technologies that allow the mitigation of environmental stresses, such as the use of regulators in seed treatment, is an alternative for crops in high temperatures regions. This study aimed to assess the heat stress mitigation on the germination and initial development of carrot seedlings using plant growth regulators. The study was divided into three experiments performed at the temperatures of 25, 30 and 35 °C. A 5 × 3 factorial arrangement was used, with fve carrot cultivars (Alvorada, Brasília, BRS Esplanada, Tellus and Tropical) and two products (Stimulate® and thiamethoxam), in addition to the control (untreated seeds). The following variables were evaluated: germination, first germination count, seedling length and dry mass. When the cultivars had their seeds treated with the plant growth regulators at 25 °C, the germination for the Tellus cultivar was 28 % higher than for the control, while, at 30 °C, the seed germination for BRS Esplanada and Tellus was twice as high as for the control, and showed a higher vigor than that of Alvorada, Brasília and Tropical. Overall, the thiamethoxam promoted increments at the initial development of carrot seedlings at 25 and 30 °C. However, the germination of the carrot cultivars was disrupted at 35 °C.

Zephyranthes sylvatica é um lindo lírio, endêmico da Caatinga brasileira. Embora tenha um grande potencial ornamental, pouco se sabe sobre esta espécie, especialmente em relação ao processo germinativo de suas sementes. Visando caracterizar a germinação de sementes de Z. sylvatica, estudou-se a sua curva de embebição, temperatura e substrato ótimos para a germinação e emergência das plântulas, tolerância aos estresses osmótico e salino, assim como a tolerância ao congelamento / descongelamento que indica o potencial crioarmazenamento a longo prazo. Baseado nos dados obtidos pode-se concluir que a germinação de Z. sylvatica apresenta modelo trifásico de embebição, em que a protrusão da raiz ocorre após 72 horas de embebição. As condições ideais para a avaliação da germinação das sementes de Z. sylvatica é de 25 ºC, em rolos de papel. Estas sementes são altamente tolerantes ao estresse osmótico, mas não ao estresse salino. Sementes de Z. sylvatica podem ser criopreservadas sem perda de germinação e vigor das sementes.

Zephyranthes sylvatica is a beautiful lily, endemic from the Brazilian Caatinga. Although it has a great ornamental potential, little is known about this species, especially regarding its seeds germination process. Aiming to characterize the germination of Z. sylvatica seeds, we studied its imbibition curve, optimum temperature and substrate for germination and seedling emergence, osmotic and salt stress tolerance, as well as the tolerance to frosting/ defrosting, which indicates long term cryostorage potential. The germination of Z. sylvatica presents a triphasic model of imbibition, in which the primary root protrusion occurs after 72 hours of imbibition. The ideal conditions for evaluating seed germination of Z. sylvatica is 25 ºC, in paper rolls. These seeds are highly tolerant to osmotic stress, but not to salt stress. Z. sylvatica seeds can be cryopreservated without loss of germination and seed vigor.