Seedlings of a range of citrus rootstocks were grown under glasshouse conditions and supplied with dilute nutrient solution containing either 0 or 50 mM NaCl. The partitioning of accumulated chloride and sodium into and within the major organs was compared between plants of Rangpur lime (Citrus reticulata var. austera hybrid?), Trifoliata (Poncirus trifoliata) and sweet orange (C. sinensis). Rootstocks differed in their leaf and stem chloride and sodium concentrations, but there was little or no difference between the rootstocks in root chloride and sodium concentrations. The lowest leaf chloride and sodium concentrations were found in the top region of shoots of all rootstocks. The different patterns of accumulation of chloride and sodium found in the three rootstocks were consistent with the existence of apparently separate mechanisms which operate to limit the transport of these two ions from the roots into the young leaves of citrus plants. The chloride excluding ability of 10 rootstocks and two hybrids was also compared and assessed in relation to rootstock vigour. Sampling from the middle leaves on salt-treated plants enabled a distinction to be made between rootstocks in their chloride accumulation properties. Cleopatra mandarin (C. reticulata), Rangpur lime, Macrophylla (C. macrophylla) and Appleby smooth Seville (C. paradisi x C. sinensis) accumulated significantly less chloride than did Trifoliata and rough lemon (C. jambhiri). Differences in chloride accumulation properties between rootstocks were unrelated to rootstock vigour.

The effects of the salinity of irrigation water on the productivity of mature grapevines was studied. We injected NaCl solutions into River Murray water to generate five salinity levels ranging from 0.37 to 3.47 dS m-l, with sodium adsorption ratios of between 2 and 37. These treatments were applied through a trickle irrigation system for six years to own-rooted sultana grapevines growing in a vineyard at Dareton, N.S.W. The effect of irrigation water salinity was most severe on vines growing in the most heavily textured soil, and increased with time. The yield ( 9 ) response was well described by the generalized logistic function:where y is yield, ECi is salinity of irrigation water, D is the theoretical yield at ECi=O, ECih is the half-effect ECi and a: is the shape parameter. Soil texture affected the response via an effect on ECih and, to a lesser extent, on a:. These parameters were related to % (silt & clay) in the final model, which was fitted for each of years 2 to 6 and accounted for 76.2% of the variance in yield.The yield response on the lightest soil most closely resembled the Maas-Hoffman 'bent-stick' model, being relatively flat at low levels of ECi and becoming steeper at moderate salinity levels. Yield losses for heavy soils were much greater than predicted by the Maas-Hoffman model. Bunch number was the primary determinant of yield, while a lower berry weight also contributed to the reduction in yield in salinized vines. Effects on dried fruit quality were apparent only when yield was severely reduced.

Grafted plants of Valencia orange scion [Citrus sinensis (L.) Osbeck] on six different rootstocks were grown under glasshouse conditions and supplied with dilute nutrient solution containing either 0 or 75 mM NaCl. Salt treatment was increased to 150 mM NaCl after 49 days. Leaf water relations and leaf chloride, sodium and potassium concentrations were followed throughout the period of salt treatment until day 105, when salt treatment ceased, and thereafter until day 140. Seedlings of Rangpur lime (C. reticulata var. austera hybrid?), Cleopatra mandarin (C. reticulata) and sweet orange (C.sinensis) were treated similarly and leaf water relations and chloride concentrations were followed until salt treatment ceased on day 77. All Valencia-rootstock combinations adjusted osmotically to the salt stress imposed and maintained turgor pressures at or above control values. Mature leaves on seedlings of sweet orange behaved similarly to Valencia orange leaves on sweet orange rootstocks by maintaining turgor pressures higher than control values. In contrast, mature leaves on seedlings of the genotypes Rangpur lime and Cleopatra mandarin tended to lose turgor during the period of treatment with 150 mM NaCl. Leaf chloride analyses indicated that Rangpur lime and Cleopatra mandarin rootstocks restricted the uptake and/or transport of chloride to shoots. However, comparatively high concentrations of sodium (>approx. 200 mM, tissue water basis) were accumulated in mature leaves on all rootstocks during salt treatment. Leaf potassium concentrations remained similar to control values. The reduction in osmotic potential in mature Valencia leaves on rough lemon (C. jambhiri), Trifoliata (Poncirus trifoliata), Camzo citrange (C. sinensis × P. trifoliata) and sweet orange rootstocks on day 77 could be accounted for largely by the increase in sodium and chloride, whereas chloride (as NaCl) accounted for only approximately 50% of the reduction in osmotic potential in Valencia leaves on Rangpur lime and Cleopatra mandarin rootstocks. Stomatal resistances in mature Valencia leaves on all rootstocks were increased by salt treatment and showed only partial recovery after the cessation of salt treatment. The incomplete recovery may have been associated with the retention in leaves of high concentrations of sodium.

This study documents changes in yield, growth, soil salinity (ECe) and leaf sodium (Na) and chlorine (Cl) concentrations in mature Valencia orange [Citrus sinensis (L.Osbeck)] trees on sweet orange (Citrus sinensis) rootstock in response to increased levels of Na and Cl in irrigation water. Four levels of salt, ranging from the river-water control (0.44 dS/m) to 2.50 dS/m, were applied over a 9-year period through an under-tree microsprinkler system to trees in the Sunraysia area of the Murray Valley in south-eastern Australia. A salt-balance model showed that evapotranspiration was reduced by salinity, whereas leaching fractions increased from an average 24% in the control to 51% in the most saline treatment. The high leaching fractions were achieved as a result of freely draining soils and good irrigation management, and allowed us to maintain low to moderate levels of soil salinity throughout the trial and minimised the effect of salt treatment on fruit yield. Soil salinity increased almost linearly in response to irrigation-water salinity during the first year, and fluctuated seasonally thereafter; however, very few readings exceeded 3 dS/m, even in the highest treatments. By contrast, leaf Na and Cl concentrations in the highest salt treatment continued to increase over the first 4 years. The relationship between yield and soil salinity was extremely weak, but yield did decrease as foliar concentrations of Na and Cl increased: in Year 9, leaf Na in the highest treatment relative to the control was associated with a predicted reduction of 17% in yield and 59% in annual trunk-diameter growth.

The paper describes the effect of varied surfactant concentrations on penetration of NaCl into leaves of Norfolk Island Pine, Araucaria heterophylla (Salisb.) Franco. It confirms that the damage observed along the sea-coast in Sydney is similar to that produced by high NaCl levels in the foliage. The effect of surfactant in increasing NaCl uptake from sea-water spray is related to the reduction in surface tension and to the advancing contact angle of the spray on the leaf surface. It is suggested that sea-spray enters A, heterophylla needles through the stomata, and that the cuticle is particularly resistant to NaCI, compared with other plant species. Similar penetration and damage was found with sprays of CaCl,, MgCl, and KC1 showing that the damage was not due specifically to NaCI.