EFFECTS OF WATERLOGGING ON THE GROWTH AND WATER RELATIONS OF 3 PINUS TAXA

The response of Caribbean pine (Pinus caribaea Morelet. var. hondurensis Barr. and Golf.), slash pine (Pinus elliottii Englem. var. elliottii) and their F1 hybrid to soil waterlogging was studied under glasshouse conditions. Plants were grown in either a lateritic or gleyed podzolic soil and pots were flooded in both autumn and summer treatments. Plant responses were influenced by both season and duration of flooding, and by soil type. All the Caribbean pine seedlings survived the autumn flooding, but showed very slow growth and had very low needle conductances. Summer-flooded plants exhibited rapid stomatal closure and low needle water-potentials accompanied by needle dehydration. All of the summer-flooded Caribbean pine seedlings died. Slash pine was much more flood-tolerant than was Caribbean pine, whilst the F1 hybrid was intermediate between the two parents. All slash pine and F1 hybrid seedlings survived autumn flooding and continued to grow, but survival was reduced with summer flooding, particularly in the short-term flooding treatment. Slash pine and F1 hybrid seedlings showed morphological features of flood tolerance with production of adventitious roots and formation of lenticels in association with stem hypertrophy. Although stomatal opening was evident during autumn flooding, needle conductance was very much reduced in summer-flooded plants of these two taxa. Needle water-potential and relative water content were maintained near the control value in flooded slash pine grown in both soil types, but only for the F1 hybrid in the flooded lateritic podzolic soil. © 1990.