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  • 1
    ISSN: 1573-5036
    Keywords: abscisic acid ; humidity effects ; rice ; root-to-shoot communication ; soil salinity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In a phytotron experiment four rice varieties (Pokkali, IR 28, IR 50, IR 31785-58-1-2-3-3) grown in individual pots were subjected to low (40/55% day/night) and high (75/90%) air humidity (RH), while soil salinity was gradually increased by injecting 0, 30, 60 or 120 mM NaCl solutions every two days. Bulk root and stem base water potential (SWP), abscisic acid (ABA) content of the xylem sap and stomatal resistance (rs) of the youngest fully expanded leaf were determined two days after each salt application. The SWP decreased and xylem ABA and rs increased throughout the 8 days of treatment. The effects were amplified by low RH. A chain of physiological events was hypothesized in which high soil electric conductivity (EC) reduces SWP, followed by release of root-borne ABA to the xylem and eventually resulting in stomatal closure. To explain varietal differences in stomatal reaction, supposed cause and effect variables were compared by linear regression. This revealed strong differences in physiological reactions to the RH and salt treatments among the test varieties. Under salt stress roots of IR 31785-58-1-2-3-3 produced much ABA under low RH, but no additional effect of low RH on rs could be found. By contrast, Pokkali produced little ABA, but rs was strongly affected by RH. RH did not affect the relationships EC vs. SWP and SWP vs. ABA in Pokkali, IR 28, and IR 50, but the relationship ABA vs. rs was strongly affected by RH. In IR 31785-58-1-2-3-3 RH strongly affected the relationship SWP vs. ABA, but had no effect on ABA vs. rs and EC vs. rs. The results are discussed regarding possible differences in varietal stomatal sensitivity to ABA and their implications for varietal salt tolerance.
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  • 2
    ISSN: 1573-5036
    Keywords: genotypic differences ; humidity effects ; panicle transpiration ; salinity ; salt resistance ; spikelet sterility ; yield components
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Salinity is a major yield-reducing stress in many arid and/or coastal irrigation systems for rice. Past studies on salt stress have mainly addressed the vegetative growth stage of rice, and little is known on salt effects on the reproductive organs. Sodium and potassium uptake of panicles was studied for eight rice cultivars in field trials under irrigation with saline and fresh water in the hot dry season and the wet season 1994 at WARDA in Ndiaye, Senegal. Sodium and potassium content was determined at four different stages of panicle development and related to salt treatment effects on yield, yield components and panicle transpiration. Yield and yield components were strongly affected by salinity, the effects being stronger in the HDS than in the WS. The cultivars differed in the amount of salt taken up by the panicle. Tolerant cultivars had lower panicle sodium content at all panicle development stages than susceptible ones. Panicle potassium concentration decreased with panicle development under both treatments in all cultivars, but to a lesser extent in salt treated susceptible cultivars. Grain weight reduction in the early panicle development stages and spikelet sterility increase in the later PDS were highly correlated (p 〈 0.01) with an increase in panicle sodium concentration in both seasons, whereas reduction in spikelet number was not. The magnitude of salt-induced yield loss could not be explained with increases in sodium uptake to the panicle alone. It is argued that the amount of sodium taken up by the panicle may be determined by two different factors. One factor (before flowering) being the overall control mechanism of sodium uptake through root properties and the subsequent distribution of sodium in the vegetative plant, whereas the other (from flowering onwards) is probably linked to panicle transpiration.
    Type of Medium: Electronic Resource
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