Effects of NaCl and CaCl₂ on Ion Activities in Complex Nutrient Solutions and Root Growth of Cotton

Abstract

Sodium displaces Ca2 from membranes (GR Cramer, A Liiuchli, VS Polito Plant Physiol 1985 79: 207-211) and this can be related to the (Ca2`)/(Na')2 activity ratio in the external solution (GR Cramer, A Lauchli 1986 J Exp Bot 37: 321-330). Supplemental Ca2" is known to mitigate the adverse effects of salinity on plant growth. In this report we investigated the effects of NaCl (0-250 millimolar) and Ca2" (0.4 and 10 millimolar) on the ion activities in solution and on root growth of cotton (Gossypium hirsutum L.). Ion activities were analyzed using the computer program, GEOCHEM. Most ion activities in a 0.1 modified Hoagland solution were significantly reduced by both NaCl and supplemental Ca2".Ion-pair formation and precipitation were significant for some ions, especially phosphate. Root growth of 6-day-old seedlings was stimulated by low NaCl concentrations (25 millimolar). At higher NaCl concentrations, root growth was inhibited; the concentration at which this occurred depended on the Ca2" concentration and the growth index used. Supplemental Ca2" mitigated the inhibition of root growth caused by NaCl.There was a curvilinear relationship between root growth and the (Ca2")/ (Na+)2 ratio in the nutrient solution. The mechanisms by which Na+ and Ca2 may affect root growth are discussed. MATERIALS AND METHODSAnalysis of Ion Activities in Nutrient Solutions. Ion activities in the nutrient solutions were calculated using the computer program, GEOCHEM (25). The rationale for the use of this program has been described previously (7). Briefly, the program calculates ion activities by a method of successive approximations, taking into consideration ion-pair formation and precipitation.Plant Growth Conditions. Cotton seeds (Gossypium hirsutum L. cv Acala SJ-2) were planted in germination paper 'sandwiches' (16). The sandwiches were inserted into slots of plastic racks which were placed in aerated treatment solutions in 3.7 L plastic containers for continual wetting of the germination paper. The tops ofthe containers were covered with BM and T multipurpose plastic wrap to minimize evaporation from the germination paper and salt accumulation. The control solution consisted of a 0.1 modified Hoagland solution (16) containing 0.4 mM Ca", with a pH of 6.5. Treatments of NaCl (0-250 mm final concentration), NaCl and supplemental Ca2" (9.6 mM CaC12 to make a 10 mm final Ca2+ concentration), or KCI (50 mM final concentration) were added to the control solution. The temperature of the nutrient solution was maintained at 27°C using a Lauda K-2/RD constant-temperature circulator. When the cotyledons emerged, the plants were irradiated with incandescent lighting (400 ,umol m-2 s-'; 15:9 h day:night cycle). Plants were harvested 6 d after the start of seed imbibition. Root growth was measured as length, fresh weight, and dry weight at harvest time.Salt stress may reduce plant growth by water deficits, ion toxicity, ion imbalance, or a combination of any ofthese factors. Cotton is one ofthe most salt-tolerant crops species (1...

Does calcium ameliorate the negative effect of NaCl on melon root water transport by regulating aquaporin activity?

“…1). This beneficial effect of calcium on the development of plants grown under saline conditions has been reported previously (Cramer et al, 1985(Cramer et al, , 1986(Cramer et al, , 1988). Short-term experiments performed by adding supplemental calcium to the saline growth media had only ameliorative effects under NaCl stress (Azaizeh & Steudle, 1991 ;Azaizeh et al, 1992).…”

“…Calcium ions are well known to have regulatory roles in metabolism, and sodium ions may compete with calcium ions for membrane-binding sites. It has been hypothesized that high calcium levels can protect the cell membrane from the adverse effects of salinity (Cramer et al, 1986). Also, calcium and apoplastic water potential have been reported to be involved in the phosphorylation of the water channel PM28A present in the spinach (Spinacia oleracea) plasma membrane (Johansson et al, 1996).…”

“…Salt stress, one of the major factors limiting crop production, may reduce plant growth by water deficit, ion toxicity, ion imbalance, or a combination of these factors (Cramer et al, 1986). However, the mechanism by which salinity inhibits growth is poorly understood (Cheeseman, 1988).…”

Influência do cálcio sobre o crescimento e solutos em plântulas de sorgo estressadas com cloreto de sódio

“…O aumento na concentração de Ca 2+ , entretanto, não teve efeito significativo sobre a produção de matéria seca das raízes no genótipo tolerante, mas resultou em redução de cerca de 11 % no genótipo sensível (Quadro 2). Os efeitos do Ca 2+ sobre o crescimento radicular de plantas submetidas a estresse salino têm-se mostrado bastante variáveis, podendo ir desde pequenas reduções, como as observadas no presente estudo, até aumentos bastante significativos, dependendo da espécie, das condições experimentais e de outros fatores (Cramer et al, 1986). O estresse salino resultou em aumento bastante elevado nos teores de Na + e de Cl -nas folhas, principalmente no genótipo sensível (Quadro 3), o que explica, pelo menos em parte, a maior sensibilidade desse genótipo ao estresse salino (Lacerda et al, 2003).…”

Mitigation of Salt Stress-Induced Inhibition of Plantago crassifolia Reproductive Development by Supplemental Calcium or Magnesium

“…For example, it has been shown that addition of Ca 2+ to root media containing NaCl favours plant growth in both halophytic (Colmer et al, 1996) and non-halophytic species (Cramer et al, 1986;Kinraide, 1999;LaHaye and Epstein, 1996;Suhayda et al, 1992). Calcium also reduced the toxic effects of Na + and Mg 2+ on the germination of Kalidum capsicum (Tobe et al, 2002) and Hordeum vulgare (Bliss et al, 1986).…”