DEVELOPMENTAL REGULATION OF ANOXIC STRESS TOLERANCE IN MAIZE

Anoxia associated with flooding stress is detrimental to plant growth and productivity. When maize seedlings 2 to 7 d old were exposed to an oxic stress, 3-d-old seedlings were found to have much lower tolerance than 2-d-old seedlings. Ninety per cent of 2-d-old seedlings survived 72 h of anoxic stress compared with 0% of the 3-d-old seedlings, Sinc e 2-d-old isolated root tips survived anoxic stress better than 3-d-ol d tips, the anoxic tolerance of 2-d-old seedlings was independent of t he translocation of nutrient reserves from the endosperm to the root, The addition of glucose to the medium improved the anoxia tolerance of 2-d-old seedlings by 25% but had no effect on 3-d-old seedlings, Accl imation by pre-exposure to 4% oxygen and pre-treatment with 100 mmol m (-3) abscisic acid (ABA) improved the anoxia tolerance of 3-d-old seed lings by 2- and 4-fold, respectively. However, acclimation and ABA tre atment had no effect on 2-d-old seedlings, The results indicate that a noxia tolerance in maize is developmentally regulated, The mechanism o f anoxia tolerance innate to 2-d-old seedlings was inducible in 3-d-ol d seedlings by acclimation or treatment with ABA.