Abstract
This study aimed to investigate the effects of growth regulators on germination rates and biochemical compound concentrations in Carica papaya L. seeds ('Formosa' group). The seeds were harvested from fruits at maturation stages 3 and 5 (50 and 75% yellow fruit skin, respectively). The effects of 2-chloroethylphosphonic acid (CEPA), KNO3 and gibberellic acid (GA3) on seed germination, germination index speed, soluble sugars, starch, lipids, soluble proteins and total proteins of the papaya seeds were evaluated. The seeds from stage 5 showed a higher rate of germination 30 days after sowing than did the seeds from stage 3. Treatment with CEPA decreased seed germination, apparently due to decreased starch mobilization; the opposite response was observed following KNO3 treatment. GA3, alone or in combination with KNO3, stimulated an increase in lipid mobilization. In general, with the exception of CEPA, all growth regulators tested were effective in overcoming seed dormancy, and KNO3 was the most effective. The seeds from stage 3 fruits treated with KNO3 or KNO3 + GA3 had higher rates of germination at 14 days.
Highlights
Dormancy can be defined as the inability of viable seeds, even under favorable conditions, to germinate (FINCH-SAVAGE; LEUBNER-METZGER, 2006)
We investigated the effects of 2-chloroethylphosphonic acid (CEPA), which is an ethylene-releasing substance, gibberellic acid (GA3) and KNO3, applied individually or in combination, on germination and reserve mobilization as a means of increasing the understanding of dormancy regulation in seeds of papaya fruits at two maturity stages
The germination percentage of seeds at stage 3 was unresponsive to CEPA concentrations ranging from 0 to 10-5 mol dm-3; the germination percentage decreased with increasing CEPA concentrations, measured at both 14 and 30 days after sowing
Summary
Dormancy can be defined as the inability of viable seeds, even under favorable conditions, to germinate (FINCH-SAVAGE; LEUBNER-METZGER, 2006). Several factors are involved in the regulation of dormancy, including hormones such as abscisic acid (ABA), gibberellins (GAs), ethylene, cytokinins and others (CARRERA et al, 2008; CHANDRA et al, 2007; FINCH-SAVAGE; LEUBNERMETZGER, 2006; HOLDSWORTH et al, 2008; RAMAIH et al, 2003; RIEFLER et al, 2006). NO3- can act as a germination promoter, possibly in association with GAs (GASHI et al, 2012). This effect appears to be independent of the reduction of NO3- to nitric oxide (NO), suggesting that NO3- may act as a germination trigger (SÁNCHEZ et al, 2010)
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