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We compared the responses of 9 palm species growing under 7 levels of shade to moderate water stress. Our objective was to compare the tolerance of these species to water deficit and to assess their irrigation requirements when grown in containers. Water stress was applied by suspending irrigation for approximately 2 weeks. Environmental conditions inside and outside the shade-house were measured throughout the development of the water stress, along with the physiological variables: leaf water potential (ψH) and stomatal resistance (rs). Changes observed (p<0.05) in those variables indicated that water stress modified the water relations of these species. Chamaedorea costaricana, Chamaedorea tepejilote, and Licuala elegans, the species that grow better under deep shade, maintained consistently high ψH values throughout the water stress. Roystonea regia, Phoenix roebelenii, and Veitchia merrillii, the species that grow well under partial shade and full sun exposure, exhibited intermediate-tohigh ψH values. Caryota mitis, Ptychosperma macarthurii, and Dypsis lutescens, exhibited consistently lower ψH values. Overall, results suggest that tropical palms grown in containers can maintain favorable water balance for 7-10 days after suspension of irrigation, water stress becomes evident after 2 weeks of water stress, and physiological recovery after rain or irrigation occurs rapidly and completely after water stress release. Our results show a buffering effect of the shade on water relations deterioration of these species, and support the use of shade in tropical agricultural systems, where solar radiation can reach excessive levels frequently and water stress occurs ubiquitously and unpredictably. [ABSTRACT FROM AUTHOR]

We evaluated the growth of 9 ornamental palm species kept under a shade gradient created by black polypropylene screens that yielded 40, 50 , 60 , 70 and 80% shade, plus a 70% aluminizednet shade treatment and a control consisting of plants grown under full sun. The species evaluated were Caryota mitis, Chamaedorea costaricana, Chamaedorea tepejilote, Dypsis lutescens, Lícuala elegans, Phoenix roebelenii, Ptychosperma macarthurii, Roystonea regia, and Veitchia merrillii. Plant height, length of the youngest fully expanded leaf, and number of leaves per plant were measured during a twoyear period. In general, plant height and leaf length were lower under 0-40% shade, increased under 50-70%, and declined under 80%. C. tepejilote, C. mitis, L. elegans y P. macarthurii behaved as obligate shade plants and did not survive under full sun. C. costaricana and D. lutescens survived full sun exposure, but their growth reached highest values under 50-60%. P. roebelenii, R. regia and V. merrillii showed reduced growth at 0-40%, but growth improved under all other shade levels employed. In general, 1-2 years are appropriate for nursering fastgrowing palms (Chamedorea spp, D. lutescens, R. regia) in tropical shade houses. Slow-growing palms (L. elegans) may be kept for 3-5 years in a shade house. Strategies for the use of shade gradients in time and space, according to the requirements and economic uses of palm species, market requirements, and plant production cycles, are discussed. [ABSTRACT FROM AUTHOR]