title: In vitro response of date palm (Phoenix dactylifera L.) to K/Na ratio under saline conditions.
abstract: BACKGROUND
  Salinity is a serious factor limiting the productivity of agricultural plants. One of the potential problems for plants growing under saline conditions is the inability to up take enough K(+). The addition of K(+) may considerably improve the salt tolerance of plants grown under salinity. It is assumed that increasing the K(+) supply at the root zone can ameliorate the reduction in growth imposed by high salinity. The present study aims to determine whether an increase in the K/Na ratio in the external media would enhance the growth of date palm seedlings under in vitro saline conditions.
  
  
  METHODS
  Date palm plants were grown at four concentrations of Na + K/Cl (mol/m(3)) with three different K/Na ratios. The 12 salt treatments were added to modified MS medium. The modified MS medium was further supplemented with sucrose at 30 g/l.
  
  
  RESULTS
  Growth decreased substantially with increasing salinity. Growth expressed as shoot and root weight, enhanced significantly with certain K/Na ratios, and higher weight was maintained in the presence of equal K and Na. It is the leaf length, leaf thickness and root thickness that had significant contribution on total dry weight. Na(+) contents in leaf and root increased significantly increased with increasing salinity but substantial decreases in Na(+) contents were observed in the leaf and root with certain K/Na ratios. This could be attributed to the presence of a high K(+) concentration in the media. The internal Na(+) concentration was higher in the roots in all treatments, which might indicate a mechanism excluding Na(+) from the leaves and its retention in the roots. K/Na ratios up to one significantly increased the leaf and root K(+) concentration, and it was most pronounced in leaves. The K(+) contents in leaf and root was not proportional to the K(+) increase in the media, showing a high affinity for K(+) uptake at lower external K(+) concentrations, but this mechanism continues to operate even with high external Na(+) concentrations.
  
  
  CONCLUSIONS
  Increasing K/Na ratios in the growing media of date plam significantly reduced the absorption of Na(+) less than 200 mM and also balance ions compartmentalization.
authors.affiliation: Environment and Natural Resources Department, College of Agriculture and Food Sciences, King Faisal University, P.O. Box 400, Hofuf, Alhassa, 31982, Kingdom of Saudi Arabia. skhateeb@kfu.edu.sa.
authors.forename: Suliman A
authors.initials: SA
authors.lastname: Alkhateeb
authors.affiliation: Agriculture Biotechnology Department, College of Agriculture and Food Sciences, King Faisal University, P.O. Box 400, Hofuf, Alhassa, 31982, Kingdom of Saudi Arabia. aalkhateeb@kfu.edu.sa.
authors.forename: Abdullatif A
authors.initials: AA
authors.lastname: Alkhateeb
authors.affiliation: Agriculture Biotechnology Department, College of Agriculture and Food Sciences, King Faisal University, P.O. Box 400, Hofuf, Alhassa, 31982, Kingdom of Saudi Arabia. solliman@yahoo.com.|Plant Biotechnology Department, National Research Centre, Dokki, 12622, Cairo, Arab Republic of Egypt. solliman@yahoo.com.
authors.forename: Mohei El-Din
authors.initials: Mel-D
authors.lastname: Solliman
mesh_terms: D065966:Absorption, Physicochemical; D002451:Cell Compartmentation / Q000502:physiology; D018556:Crops, Agricultural; D066298:In Vitro Techniques; D065749:Phoeniceae / Q000254:growth & development / Q000502:physiology*; D018515:Plant Leaves / Q000378:metabolism; D018517:Plant Roots / Q000378:metabolism; D018520:Plant Shoots / Q000378:metabolism; D011188:Potassium / Q000378:metabolism*; D054712:Salinity; D012964:Sodium / Q000378:metabolism*; D013395:Sucrose / Q000494:pharmacology
chemical_list: D013395:Sucrose; D012964:Sodium; D011188:Potassium