4. Discussion
Nitric oxide (NO) plays a vital role in different developmental
processes ranging from leaf expansion, root growth and senescence
[55,56]. Besides being involved in wounding and pathogen
interactions [38], NO has proven to contribute to
ethylene biosynthesis [17]. However, some studies found that
NO represses ethylene biosynthesis [41]. The level of cellular
NO is mediated by several factors, including the presence of
Hbs, which are effective regulators of NO. As reviewed by Hill
[18], both the Arabidopsis Glb1 and Glb2 are able to reduce