EARLY FLOODING OF TWO CULTIVARS OF TROPICAL MAIZE. I. SHOOT AND ROOT GROWTH

Abstract

Maize (Zea mays L.) crop growth and development are disrupted when the soil is subjected to transient flooding, especially if the stress occurs early during the vegetative phase. Our understanding however, is limited regarding the physiological basis of field tolerance to flooding. Closer examination of adapted tropical cultivars is also required, because limited-resource farmers find drainage systems unaffordable. In this study we examine the short-term damage and acclimation of two tropical varieties of maize, during a six-day period of soil flooding, and their recovery, early during the vegetative stage. Two Venezuelan varieties, one considered tolerant and the other susceptible to poor soil drainage, were planted in 10 kg pots, and were flooded at the seventh leaf-tip (V4) stage for six days, and their responses compared to corresponding non-flooded plants. Shoot biomass was reduced in both varieties by 20 to 50% because of flooding. The tolerant variety however, placed a larger proportion of biomass into the root system, both during the flooding and afterwards. Leaf area was reduced by 40% in both cultivars. Plants continued elongating their youngest adventitious roots when flooded. These roots developed increased porosity (aerenchyma) and only first order laterals. The tolerant cultivar produced 30% more aerenchyma than the susceptible one, but maintained lower rates of respiration. Older adventitious roots and seminal roots experienced extensive damage by flooding and did not recover 10 days after drainage. Flooding accelerated root development, by early activation of new nodes with adventitious roots, while shoot development was less affected. Upon drainage, root systems proliferated very rapidly, retaining the aerenchymatous tissue. Our results indicate that tolerance of maize plants to soil inundation was associated with moderate root respiration rates and abundant root aerenchyma.