WATER STRESS IN METABOLISM AND INITIAL GROWTH OF MUTAMBO (Guazuma ulmifolia Lam.) SEEDLINGS

Este trabalho teve como objetivo avaliar o crescimento inicial das mudas de Guazuma ulmifolia (mutambo) sob diferentes regimes hídricos. As mudas receberam os seguintes tratamentos de água: 100%, 50%, 25% e 12,5% da capacidade de campo e foram avaliadas aos 35 e 83 dias de cultivo nos diferentes tratamentos. A sobrevivência das mudas a 12,5%cc foi menor que nos demais tratamentos, podendo ser avaliadas apenas aos 35 dias. A altura, diâmetro, área foliar, massas seca de parte aérea e raiz foram maiores sob maior disponibilidade de água, entretanto o comprimento médio das raízes não variou entre os tratamentos. A condutância estomática, fotossíntese e transpiração foram menores sob 12,5%cc, porém a eficiência no uso da água não variou entre as diferentes cc. A taxa assimilatória líquida, taxa de crescimento relativo, razão de área foliar e a abertura dos ostíolos diminuíram com as menores cc. Para a produção de mudas de Guzuma ulmifolia o regime hídrico na fase inicial deve ser de 100% da capacidade de campo, porém as mudas crescem satisfatoriamente sob 50%cc. Abaixo de 25%cc as mudas entram em estresse hídrico antes dos 35 dias de cultivo.This work aimed to evaluate the initial growth of Guazuma ulmifolia (mutambo) seedlings under different water regimen. The seedlings received the following treatments of water: 100%, 50%, 25% and 12.5% of the capacity of field and were evaluated in 35 and 83 days of cultivation in different treatments. The seedlings survival in 12.5%cc was smaller than in others treatments, being evaluated only on 35 days after the seedlings did not resist, lost completely the leaf and died. The height, diameter, the leaf area, dry mass of airy part and roots were higher under high water availability, however the medium length of the roots did not vary among the treatments. The stomatal conductance, photosynthesis and transpiration rates were lower under 12.5%cc, but the efficiency in the use of water did not vary between the different cc. The rate of liquid assimilated and relative growth, leaf area ratio and opening of ostioles decreased with low field capacity. To the production of seedlings of Guzuma ulmifolia the water regimen in initial phase must be of 100%cc, however the seedlings growth is satisfactory below 50%cc. Bellow of 25%cc the seedlings get in water stress before the 35 days of cultivation