title: Effects of external potassium (k) supply on drought tolerances of two contrasting winter wheat cultivars.
abstract: BACKGROUND
  Drought is a common stress limiting crops growth and productivities worldwide. Water deficit may increase cellular membrane permeability, resulting in K outflow. Internal K starvation may disorder plant metabolism and limit plant growth. However, it is seldom reported about the effects of external K on drought tolerance of contrasting wheat cultivars.
  
  
  RESULTS
  A hydroponics experiment was carried out in a non-controlled greenhouse. Seedlings of drought-tolerant SN16 and intolerant JM22 were simultaneously treated by five levels of K2CO3 (0, 2.5, 5, 7.5, 10 mM) and two levels of PEG6000 (0, 20%) for 7 days. External K2CO3 significantly increased shoot K(+) content, water potential, chlorophyll content as well as gas exchange, but decreased electrolyte leakage (EL) and MDA content in both cultivars under PEG6000 stress. Antioxidant enzymes activities were up-regulated by PEG6000 while external K2CO3 reduced those changes. Molecular basis was explained by measuring the expression levels of antioxidant enzymes related genes. Shoot and root biomass were also increased by K2CO3 supply under drought stress. Although adequate K2CO3 application enhanced plant growth for both cultivars under drought stress, SN16 was better than JM22 due to its high drought tolerance.
  
  
  CONCLUSIONS
  Adequate external K may effectively protect winter wheat from drought injuries. We conclude that drought-tolerant wheat combined with adequate external K supply may be a promising strategy for better growth in arid and semi-arid regions.
authors.affiliation: State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, the Chinese Academy of Sciences, Beijing, PR China.
authors.forename: Jiguang
authors.initials: J
authors.lastname: Wei
authors.forename: Caihong
authors.initials: C
authors.lastname: Li
authors.forename: Yong
authors.initials: Y
authors.lastname: Li
authors.forename: Gaoming
authors.initials: G
authors.lastname: Jiang
authors.forename: Guanglei
authors.initials: G
authors.lastname: Cheng
authors.forename: Yanhai
authors.initials: Y
authors.lastname: Zheng
mesh_terms: D000064:Acclimatization / Q000187:drug effects*; D000975:Antioxidants / Q000378:metabolism; D018533:Biomass; D002254:Carbonates / Q000494:pharmacology* / Q000600:supply & distribution; D002734:Chlorophyll / Q000378:metabolism; D055864:Droughts; D005740:Gases / Q000378:metabolism; D008315:Malondialdehyde / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects / Q000378:metabolism; D018520:Plant Shoots / Q000187:drug effects / Q000378:metabolism; D011188:Potassium / Q000494:pharmacology* / Q000600:supply & distribution; D012621:Seasons; D014908:Triticum / Q000187:drug effects* / Q000254:growth & development / Q000502:physiology; D014867:Water / Q000378:metabolism
chemical_list: D000975:Antioxidants; D002254:Carbonates; D005740:Gases; D014867:Water; D002734:Chlorophyll; D008315:Malondialdehyde; C037593:potassium carbonate; D011188:Potassium