Trade Winds Reduce Growth and Influence Gas Exchange Patterns in Papaya Seedlings

Abstract

Four experiments were conducted to determine the effect of trade winds in Guam, USA, on growth and gas exchange of three papaya (Carica papaya L.) cultivars. ‘Known You 1’, ‘Sunrise’, and ‘Tainung 2’ papaya seedlings at two different stages of development were exposed to 0, 36 or 100% ambient wind. Wind exposure reduced stem height and leaf or stem dry weight in most cases, but had little influence on root growth. Net CO2assimilation (ACO2) at midday was lower for seedlings exposed to wind than for those protected from wind. Dark respiration of exposed seedlings increased as much as 120% above that of the protected seedlings during the night. Wind exposure decreased whole plant evapotranspiration by up to 36% during the photoperiod, but increased evapotranspiration by 58–87% during the nocturnal period. Responses to wind exposure were similar among cultivars, except that growth of ‘Tainung 2’ seedlings was less affected by wind than that of the other cultivars. Seedlings that were exposed to the various wind treatments from germination onwards were less influenced by wind exposure than were seedlings that were grown in a protected nursery before being exposed to the various wind treatments. These data indicate that: (1) ambient trade winds in Guam are strong enough to decrease the growth of papaya seedlings; (2) plant age influences the response; (3) stem and leaf growth are more influenced than root growth; and (4) decreasedACO2 and increased dark respiration may be partly responsible for growth reduction.