02260naa a2200169 a 450000100080000000500110000800800410001910000230006024502220008326000090030552016260031465000220194065000100196265000150197270000190198777300840200620563442016-11-14       2001    bl uuuu     u00u1 u    #d1 aSOUZA, I. R. P. de  aGibberellic acid and dwarfism effects on the growth dynamics of B73 maize (Zea mays L.) leaf bladesba transient increase in apoplastic peroxidase activity precedes cessation of cell elongation.h[electronic resource]  c2001  aThe relationship between apoplastic peroxidase (EC 1.11.1.7) activity and cessation of growth in maize) Zea mays L.) leaf blades was investigated by altering elongation zone length. Apoplastic peroxidase activity in the elongation and secondary cell wall deposition zones of elongating leaf blades of the maize inbred line B73 was used as a control and compared to leaves of the dwarf mutant D8-81127, a near-isogenic line of B73 unresponsive to gibberellins, and to leaves of B73 plants to which gibberellic acid (GA 3) had been applied via root uptake. Elongation zone length was increased by treatment with GA 3 through an increase in cell number as well as increased final cell length. The shorter elongation zone of dwarf leaves occurred primarily through reduced final cell length. Although elongation zone length differed among dwarf, control, and GA 3 -treated leaf blades, in all three treatments a transient increase in apoplastic peroxidase activity preceded a reduction in the segmental elongation rate in leaves. A peroxidase isoenzyme with p I7.0 occurred in the leaf elongation zone during growth deceleration in all three treatments, and its activity decreased as growth displaced tissue into the region of secondary cell wall deposition. Growth cessation for all treatments coincided with the first appearance of peroxidase isozymes with pIs of 5.6 and 5.7. Based on the activity of particular isozymes relative to growth and differentiation, the p I7.0 isoenzyme is most likely to be involved in cessation of cell elongation, while isozymes with pIs 5.6 and 5.7 are likely to be active in lignification.  aÁcido giberelico  aMilho  aPeroxidase1 aMACADAM, J. W.  tJournal of Experimental Botany, Londongv. 52, n. 361, p. 1673-1682, Aug. 2001.