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Pregerminative seed treatments and seedlings emergence of Opuntia streptacantha Lem

Abstract:

Seeds of Opuntia have physiological dormancy, needing an after-ripening period to break dormancy and embryos with low germination potential. Morphophysiological and biochemical studies of Opuntia seedlings and the comparison between species are limited by the lack of methodology to the seed germination and to obtain seedlings. The objective of the study was to evaluate pregerminative treatments of seeds in the emergence and growth seedlings of O. streptacantha Lem. A completely randomized design was used with three replications, the seedling emergency was evaluated every 3 d for 40 d after sowing (DAS) in substrate of coconut shaving and vermicompost (1:1). The treatments were: control, seed immersion in hot water (98°C; 5 min)/cooling at 20ºC, soaked in water at 20ºC/24 h and seeds soaked for 30 min in 5% acetic acid. The experimental unit was a group of 50 seeds per treatment and per replication. The time for seedlings emergency, number of emerged seedlings, number of roots per seedling and seedlings dimensions were evaluated. The treatment of hot water totally inhibited the emergence of seedlings. Seedling emergency of control began 7 DAS and the other treatments retarded it 3-4 d. Maximum seedling emergence amounted 48% and took between 22 and 31 d (P>0.05) and the number of roots per seedling was not different among treatments. The seedlings obtained from the control (17.5 cm) were 21% taller and its root and hypocotyl reached 20 and 23% greater length than the other two treatments. The treatments to stimulate seed germination of O. streptacantha were inefficient to increase the emergence and growth of the seedlings. The seedlings emergency of this species appeared to be related with relatively high daytime and night-time temperatures (33.6 and 27.1°C) during the emergency.