Sap flow sensors were installed on the leaf petioles of 5-year-old oil palms (Elaeis guineensis Jacq.) to measure the xylem water flow for 12 days based on the heat ratio method (HRM). It was found that young leaves have higher sap flow rates, reaching values of over 250 cm3 h-1, and that sap flow fluctuations are directly related to weather conditions, particularly the vapor pressure deficit (VPD) component. It was observed that the sap flow rates remained constant and very close to 0 cm3 h-1 between 18:00 and 6:00 h and that the upward and downward movement of sap was faster during the day, with peak levels between 9:00 and 16:00 h. Under the evaluation conditions, the oil palm crop transpiration was estimated to be 1.15 mm H2O/ha-day. The HRM is a highly repeatable method and an useful tool to quantify the total oil palm transpiration. It could potentially be applied to irrigation.
Oil palm is the most productive and efficient oilseed crop in the world. Oil palm is planted in various geographical areas, where the frequency of extreme weather events is expected to increase because of climate change. The characterization of the response of oil palm cultivars to climatic conditions will allow identifying sources of tolerance to different types of stress caused by climate change, leading to the determination of the best genotype x environment relationships. The physiological responses, oil quality and yield of 11, six-year-old commercial oil palm cultivars with different origins were evaluated in two periods of contrasting climate conditions (rainy and dry seasons between the years 2008 and 2010). We found that the first impact of a period with water deficit was the reduction on gas exchange of all cultivars. Photosynthesis fell between 25% to 40% and transpiration decreased between 10% and 50%. During the dry season, leaf sugar concentration increased respect to the rainy season between 14% to 114%, and certain cultivars showed up to 27% higher photosynthetic water use efficiency. This variation could be due to the genetics of different cultivars. No significant differences were observed between the seasons in terms of oil quality. In general, changes in oil palm physiology observed in response to water deficit were related to the ability of the palm to adapt and survive periods of drought stress. The cultivars evaluated showed a good response to dry periods, with the IRHO being the most outstanding at each evaluated season .
Elaeis guineensis palms and its interspecific hybrid (E. oleifera x E. guineensis) were planted in 2004 in the Cuernavaca farm of Unipalma S.A., located in the municipality of Paratebueno (Cundinamarca, Colombia). The palms were planted in two fields: Mecasaragua and Aurora. The first field has never been irrigated, and the second one (Aurora) has always been flood-irrigated during the dry season according to the parameters of the plantation. In this study, physiological parameters (gas exchange and water potential) were assessed in three seasons of the year 2013 (dry season, dry-to-wet transition season and wet season). Significant gas exchange differences were found among the seasons in the field with no irrigation (Mecasaragua). Likewise, differences between the genetic materials were observed during the dry season. For example, the photosyn thesis decreased by 75% compared with the palms planted in the irrigated field. No differences among seasons or materials were found in the irrigated field (Aurora). E. guineensis palms were more sensitive to water stress compared with the OxG interspecific hybrid. Both genetic materials responded rapidly to the first rains by leveling their photosynthetic rates and demonstrated an excellent capacity to recover from water stress.
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