Allelopathic effects of hydroxamic acids from sugarcane leaves on germination and growth of crops

The allelopathic effects of 2,4-dihydroxy-1,4-benzoxazin-3-one, isolated from sugarcane leaves and its decomposition product, 2-benzoxazolinone was evaluated on germination and growth of sugarcane (interspecific hybrids of Saccharum), wheat (Triticum aestivum L.), mustard (Brassica campestris L.) and mung bean (Vigna radiata L.). The 2,4-dihydroxy-1,4-benzoxazin-3-one and 2-benzoxazolinone at concentrations > 0.3 mM significantly inhibited the germination of sugarcane and completely inhibited > 0.6 mM concentrations. Both hydroxamic acids also significantly reduced the number of leaves per plant, plant height and dry weight of sugarcane. The 0.3–0.7 mM concentrations caused 15–40% inhibition, however, the maximum reduction was observed at 0.8 mM. Both hydroxamic acids < 0.3 mM had no adverse effects on sugarcane germination. However, they completely inhibited seed germination of wheat and mustard > 0.5 mM concentrations and caused 90% inhibition in mung bean seeds.