Potassium deficiency affects water status and photosynthetic rate of the vegetative sink in green house tomato prior to its effects on source activity

• Published in: Plant science (Limerick) 2011-02, Vol.180 (2), p.368-374
• Main Authors: Kanai, Synsuke, Moghaieb, Reda E., El-Shemy, Hany A., Panigrahi, R., Mohapatra, Pravat K., Ito, J., Nguyen, Nguyen T., Saneoka, Hirofumi, Fujita, Kounosuke
• Format: Article
• Language: English
• Subjects: Aquaporin; aquaporins; Aquaporins - antagonists & inhibitors; Aquaporins - metabolism; Biological and medical sciences; Biological Transport; Biomass; Carbon Dioxide - metabolism; Carbon Isotopes; diameter; Fundamental and applied biological sciences. Psychology; greenhouse production; Hydroponics; K-channel; leaf water potential; Lycopersicon esculentum - anatomy & histology; Lycopersicon esculentum - growth & development; Lycopersicon esculentum - metabolism; Micro-morphometric method; nutrient deficiencies; photosynthates; Photosynthesis; Plant Leaves - growth & development; Plant Leaves - metabolism; plant nutrition; Plant Roots - growth & development; Plant Roots - physiology; Plant Stems - anatomy & histology; Plant Stems - growth & development; Plant Stems - metabolism; Plant Stomata - metabolism; Plant Transpiration - physiology; plant-water relations; potassium; Potassium - metabolism; Potassium - pharmacology; potassium channels; Potassium Channels - metabolism; Potassium deficiency; root hydraulic conductivity; Silver Nitrate - pharmacology; Solanum lycopersicum; source-sink relationships; Stem diameter; stems; Tomato; tomatoes; transpiration; transport proteins; Water - metabolism; water uptake
• ISSN: 0168-9452; 1873-2259
• DOI: 10.1016/j.plantsci.2010.10.011

▶ New insight and close relationship between K-channel and aquaporin. ▶ The initial response of K-deficiency stress was perceived in the form of a change in K-channel activity. ▶ Coupling between aquaporins and K-channel transporters in water uptake of roots is responsible for regulation of stem diameter dynamics. The potassium requirement of green house tomatoes is very high for vegetative growth and fruit production. Potassium deficiency in plants takes long time for expression of visible symptoms. The objective of this study is to detect the deficiency early during the vegetative growth and define the roles of aquaporin and K-channel transporters in the process of regulation of water status and source–sink relationship. The tomato plants were grown hydroponically inside green house of Hiroshima University, Japan and subjected to different levels of K in the rooting medium. Potassium deficiency stress decreased photosynthesis, expansion and transport of 14C assimilates of the source leaf, but the effects became evident only after diameter expansion of the growing stem (sink) was down-regulated. The depression of stem diameter expansion is assumed to be associated with the suppression of water supply more than photosynthate supply to the organ. The stem diameter expansion is parameterized by root water uptake and leaf transpiration rates. The application of aquaporin inhibitor (AgNO 3) decreased leaf water potential, stem expansion and root hydraulic conductance within minutes of application. Similar results were obtained for application of the K-channel inhibitors. These observations suggested a close relationship between stem diameter expansion and activities of aquaporins and K-channel transporters in roots. The deficiency of potassium might have reduced aquaporin activity, consequently suppressing root hydraulic conductance and water supply to the growing stem for diameter expansion and leaf for transpiration. We conclude that close coupling between aquaporins and K-channel transporters in water uptake of roots is responsible for regulation of stem diameter dynamics of green house tomato plants.