Department of Biosciences , Saurashtra University , Rajkot 360005, Gujarat , India.
AoB Plants. 2010;2010:plq011. doi: 10.1093/aobpla/plq011. Epub 2010 Jul 21.
Mangroves of Western Gujarat (India) are subject to die-back. Salinity intolerance is one possible cause, especially in young plants. We therefore quantified the extent to which young plants of one widely occurring mangrove species (Ceriops tagal) tolerate high salt in terms of establishment, growth, water status, proline content and mineral accumulation.
In a greenhouse study, juvenile plants were established from mature propagules over 40 days in soil containing added NaCl, raising soil water salinity to 0.2, 2.5, 5.1, 7.7, 10.3, 12.6, 15.4, 17.9, 20.5 and 23.0 ppt (w/v). Growth and physiological characteristics were monitored over the subsequent 6 months.
Despite a negative relationship between the percentage of young plant establishment and salt concentration (50 % loss at 22.3 ppt), the remaining plants proved highly tolerant. Growth, in dry weight, was significantly promoted by low salinity, which is optimal at 12.6 ppt. Water content, leaf expansion and dry matter accumulation in tissues followed a similar optimum curve with leaf area being doubled at 12.6 ppt NaCl. Salinity >12.6 and <23 ppt inhibited plant growth, but never to below control levels. Root:shoot dry weight ratios were slightly reduced by salinity (maximum 19 %), but the water potential of roots, leaves and stems became more negative as salinity increases while proline increases in all tissues. The concentration of Na increased, whereas concentrations of K, Ca, N and P decreased and that of Mg remained stable.
Ceriops tagal has a remarkably high degree of salinity tolerance, and shows an optimal growth when soil water salinity is 12.6 ppt. Salinity tolerance is linked to an adaptive regulation of hydration and ionic content. The cause of localized die-back along the coastal region of Gujarat is thus unlikely to be a primary outcome of salinity stress although amendments with Ca and K, and perhaps proline, may help protect against extreme salinity.
印度古吉拉特邦西部的红树林面临衰退。盐度不耐受是一个可能的原因，特别是对幼树而言。因此，我们以一种广泛分布的红树林物种（桐花树）的幼树为研究对象，量化了它们在盐度胁迫下的建立、生长、水分状态、脯氨酸含量和矿物质积累的程度。
在温室研究中，我们从成熟的繁殖体中培养出幼年植物，在含有添加 NaCl 的土壤中培养 40 天，将土壤水盐度提高到 0.2、2.5、5.1、7.7、10.3、12.6、15.4、17.9、20.5 和 23.0 ppt（w/v）。在随后的 6 个月中监测生长和生理特征。
尽管幼树建立的百分比与盐浓度呈负相关（22.3 ppt 时损失 50%），但其余的植物证明具有很强的耐盐性。在低盐度下，植物的生长（以干重计）显著增加，最适盐度为 12.6 ppt。水分含量、叶片扩张和组织中干物质积累也遵循类似的最佳曲线，叶片面积在 12.6 ppt NaCl 时增加一倍。盐度 >12.6 和 <23 ppt 抑制植物生长，但从未低于对照水平。根：茎干重比受盐度略有降低（最大 19%），但随着盐度的增加，根、叶和茎的水势变得更加负，而脯氨酸在所有组织中增加。Na 的浓度增加，而 K、Ca、N 和 P 的浓度降低，Mg 的浓度保持稳定。
桐花树具有很高的耐盐度，当土壤水盐度为 12.6 ppt 时，生长最佳。耐盐性与水合和离子含量的适应性调节有关。因此，古吉拉特邦沿海地区局部衰退的原因不太可能是盐度胁迫的主要结果，尽管添加 Ca 和 K，也许还有脯氨酸，可以帮助抵御极端盐度。
