The importance of bracteoles in ensuring atriplex halimus germination under optimal conditions

Atriplex halimus L. is a native halo-nitrophilous scrub that grows in salt-marsh environments and saline soils of the Mediterranean basin. The presence of bracteoles did not change the germination rate of seeds and fruits (seeds with bracteoles) in water, although bracteoles did slow down the process, from 2.5 to 5.7 days to reach the 50% of the final germination in seeds and fruits, respectively. Bracteoles prevented germination NaCl solutions greater than 0.3M. The seeds without bracteoles germinated at concentrations higher than 0.3M NaCl, but had smaller cotyledons than seeds germinated in water (3.1 and 5.6 mm, respectively), and all the roots had necrotic zones. The results showed that bracteoles play an important role in preventing seeds from germinating in NaCl concentrations higher than 0.3M, ensuring that they remained dormant and only germinated when freshwater was available. The recovery experiments showed that the seeds from the fruits that did not germinate in salt were not unviable, but remained dormant, awaiting the proper conditions to germinate. In the presence of water, the final germination was higher than 95%, and there was little necrosis found in the roots. The results showed how the presence of bracteoles prevented germination under unfavourable conditions for plant development.