盐碱混合胁迫下抗碱盐生植物碱地肤的生长及其茎叶中溶质积累特点

将中性盐NaCl、Na2SO4和碱性盐NaHCO3、Na2CO3按不同比例混合,模拟出25种盐度、碱度各不相同的复杂盐碱条件,并对抗碱盐生植物碱地肤幼苗进行盐碱混合胁迫处理。测定其茎叶中溶质含量及日相对生长率等9项胁变指标,并分析了有机酸组分。以探讨混合盐碱胁迫下,碱地肤的生长及其茎叶中溶质积累特点。结果表明,适当的中性盐胁迫(80 mmol/L)对其生长有促进作用,而后随着盐度或碱度的增强其日相对生长率逐渐下降。在本实验条件下,碱地肤幼苗可耐受的最高盐碱混合胁迫强度为盐度400 mmol/L、pH值10.70,可见碱地肤是一种高度抗碱的盐生植物。在各种盐碱混合胁迫下,碱地肤茎叶中各种溶质的积累表现出了与众不同的特点。大量积累以Na 、K 为主的无机离子。Na 、K 含量均随盐度增强而上升,而且K /Na 基本保持不变(约为0.49),表明了碱地肤对K 、Na 吸收可能不存在拮抗作用。盐度是影响Na 、K 含量的主导因素,而碱度的影响较小。大量积累的有机溶质是甜菜碱和有机酸。随着盐度或碱度的增强甜菜碱的含量逐渐上升,最高含量可达干重的6%。盐度对甜菜碱积累的影响大于碱度。在积累的有机酸中,草酸的比例高达90%以上。有机酸含量不仅随盐度增高而上升,而且碱度对其也有明显的提高作用。只有在盐度大于240 mmol/L或pH值超过9.8的高强度的盐碱胁迫下,脯氨酸才有所积累,而且其积累量平均仅为甜菜碱的1/74左右。这一现象表明碱地肤茎叶中脯氨酸的积累可能不是一种单纯的对渗透胁迫的生理响应。

A characteristic of the growth and solute accumulation in shoots of an alkali-tolerant Kochia sieversiana under salt-alkaline mixed stress

The seedlings of an alkali-tolerant Kochia sieversiana were stress treated under 25 salt-alkaline mixtures which were established by mixing two neutral salts(NaCl and Na2SO4) and two alkali salts(NaHCO3 and Na2CO3) in various proportions.Nine physiological indices including contents of various solutes in shoots and relative growth rate(RGR) were determined.Components of organic acids were analyzed,to explore the traits of growth and solute accumulation by K.sieversiana under mixed salt-alkaline stresses. Growth of K.sieversiana seedlings was stimulated at moderate neutral salt stress(80 mmol/L),and above this point,the RGR decreased gradually with increasing salinity or alkalinity.In the experimental conditions,the highest stress intensity that K.sieversiana could was 400 mmol/L of salinity and pH value 10.70,which proved that K.sieversiana was a halophyte species with high alkali-tolerance.The various solute accumulations in the shoots of K.sieversiana showed a larruping trait under various salt-alkaline mixed stresses.The inorganic ions Na and K as dominant components largely accumulated.The contents of Na and K both increased with increasing salinity,and the values of K /Na were basically steady(approximate 0.49).It indicated that there was no competition between K and Na for absorption.Salinity was the dominant effect factor for Na and K contents and the effects of alkalinity were less.In organic solutes,betaine and organic acid were accumulated.The content of betaine increased with increasing salinity or alkalinity,with its highest value up to 6% of dry weight.The effect of salinity on the content of betaine was greater than that of alkalinity.In the accumulated organic acid,the proportion of oxalic acid was upwards of 90%.The content of organic acid not only increased with increasing salinity not only,but was also significantly promoted by alkalinity.Significant accumulation of proline occurred only under intense mixed salt-alkaline stress such as salinity over 240 mmol/L or pH value over 9.80,and its quantity was only about 1/74 of betaine.It indicated that the proline accumulation in the shoots of K.sieversiana might be not a simplex physiological response to osmotic stress.