ROOT AND SHOOT GROWTH-PATTERNS IN 4 PALM SPECIES AND THEIR RELATIONSHIPS WITH AIR AND SOIL TEMPERATURES

Royal palms [Roystonea regia (HBK.) O.F. Cook], coconut palms (Cocos n ucifera L. 'Malayan Dwarf), queen palms [Syagrus romanzoffiana (Chamis so) Glassman], and pygmy date palms (Phoenix roebelenii O'Brien) were grown in a rhizotron to determine the patterns of root and shoot growt h over a 2-year period. Roots and shoots of all four species of palms grew throughout the year, but both root and shoot growth rates were po sitively correlated with air and soil temperature for all but the pygm y date palms. Growth of primary roots in all four species was finite f or these juvenile palms and lasted for only 5 weeks in royal palms, bu t approximate to 7 weeks in the other three species. Elongation of sec ondary roots lasted for only 9 weeks for coconut palms and less than h alf of that time for the other three species. Primary root growth rate varied from 16 mm.week(-1) for coconut and pygmy date palms to 31 mm. week(-1) for royal palms, while secondary root growth rates were close to 10 mm.week(-1) for all species. About 25% of the total number of p rimacy roots in these palms grew in contact with the rhizotron window, allowing the prediction of the total root number and length from the sample of roots visible in the rhizotron. Results indicated that there is no obvious season when palms should not be transplanted in souther n Florida because of root inactivity.