Effect of methyl jasmonate treatments on alleviation of polyethylene glycol -mediated water stress in banana (Musa acuminata cv. 'Berangan', AAA) shoot tip cultures

The role of exogenous methyl jasmonate (MeJA) application in moderating in vitro water stress on banana growth was investigated. Shoot tips were treated using various levels (0, 5, 10, 20, 40, 80, 100, 120, 140 and 160 mu M) of MeJA before and during the imposition of 30 g L-1 PEG induced water stress in the media. Proliferation rate significantly improved with increasing doses of MeJA up to 80 mu M whether the shoot tips were stressed by PEG or unstressed. The same trend was observed in terms of enhanced fresh weight increase and shoot vigour rate under water stress. PEG significantly reduced the relative water content (%) of shoot tips by about 35 % as compared with those of unstressed conditions, while MeJA application up to 40 mu M reduced the inhibitory effect of PEG on leaf water loss (%). Shoot tips under water stressed conditions, responded positively to MeJA by exhibiting a significant increase in proline, although increasing levels to 100 mu M and higher had no effect. MeJA alleviated the effect of PEG-induced loss of chlorophyll, although it had no additional benefit by altering the dosages. Under water stress, MeJA application up to 40 mu M was also effective in reducing oxidative injury as indicated by significant reduction in H2O2 and MDA contents of shoot tips; higher dosages exhibited no further advantageous effect. These results suggested the participation of MeJA in improving drought tolerance of banana and moderating oxidative stress leading to enhanced plant performance.