盐磷胁迫对木麻黄和台湾相思种子萌发及幼苗生长的影响

Effects of salt and phosphorus stress on seed germination and seedling growth of Casuarina equisetifolia and Acacia confusa

关键词:  养分胁迫, 木麻黄, 台湾相思, 种子萌发, 幼苗生长

Key words:  Nutrient stress, Casuarina equisetifolia, Acacia confusa, seed germination, seedling growth

摘要:

恶劣环境下,人工海防林因面临养分胁迫而经营困难。为探讨盐、磷胁迫对主要海防林树种木麻黄和台湾相思种子萌发及生长的影响,该研究分别用不同浓度的NaCl(盐)和KH₂PO₄(磷)溶液处理种子和浇灌幼苗,测定种子萌发和幼苗生长指标。结果表明:(1)高盐胁迫显著抑制种子萌发,对幼苗生长有一定影响,但两种植物影响程度不同; 台湾相思种子萌发耐盐性高于木麻黄,前者相对盐害率最大值为23.03%,后者为89.15%; 随着盐浓度增加,木麻黄和台湾相思种子的发芽率、发芽势、发芽指数和活力指数均降低,对应最大值分别为38.70%、34.67%、18.70、0.055和76.67%、62.22%、48.46、6.11。(2)两种植物的株高和根长随盐浓度增加而降低,木麻黄和台湾相思株高分别为12.29～6.01 mm和48.27～17.33 mm,根长分别为8.57～1.45 mm和33.41～5.88 mm; 台湾相思根、茎、叶生物量及根冠比均随盐浓度的增加逐渐减小,木麻黄各处理差异较小。(3)台湾相思的种子和幼苗较木麻黄更耐低磷环境,二者最适磷浓度存在差异; 木麻黄种子发芽率(49.33%)、发芽指数(23.12%)、活力指数(0.093)及根茎叶生物量最大值均在0.1 mmol·L^-1磷处理; 台湾相思种子发芽率(81.11%)、发芽势(62.22%)、发芽指数(38.23)、活力指数(5.07)、株高(54.48 mm)及根长(37.16 mm)最大值均在5 mmol·L^-1磷处理,10 mmol·L^-1磷处理抑制其萌发。因此,播种海防林种子或种植幼苗时须根据土壤盐和磷的含量选择播种或种植方式。

Abstract:

Artificial coastal protection forests are difficult to manage because of nutrient stress in harsh environment. To explore the effects of salt and phosphorus stress on the seed germination and seedling growth of Casuarina equisetifolia and Acacia confusa, we respectively watered the seeds and seedlings of the two kinds of plants with the solutions of NaCl(salt)and KH₂PO₄(phosphorus)in different concentrations, and then determined their growth indicators, respectively. The results were as follows:(1)High salt concentration solutions significantly inhibited seed germination and had a certain effect on the growth of seedlings, however, the effects of salt stress on seed gemination and growth were different. The salt tolerance of Acacia confusa seed germination was higher than that of Casuarina equisetifolia. The biggest relative salt damage rate of Acacia confusa was 23.03% and that of Casuarina equisetifolia was 89.15%. As the concentration of NaCl increased, the germination rate, germination potential, germination index and vitality index of Casuarina equisetifolia and Acacia confusa seeds decreased. And the maximums of the four germination indexes of Casuarina equisetifolia seed were 38.70%, 34.67%, 18.70 and 0.055, and of Acacia confusa seeds were 76.67%, 62.22%, 48.46 and 6.11, respectively.(2)The height and root length of the plants decreased with the increase of salt concentration. The plant heights of Casuarina equisetifolia and Acacia confusa were 12.29 to 6.01 mm and 48.27 to 17.33 mm, and the root lengths were 8.57 to 1.45 mm and 33.41 to 5.88 mm, respectively. The biomass of root, stem and leaf as well as root shoot ratio of Acacia confusa gradually decreased with the increase of salt concentration, but the differences between the treatments of Casuarina equisetifolia were not obvious. 0.6% and 0.4% salt stress were the thresholds for seed germination and seedling growth of the two plants, respectively.(3)The seed and seedling of Acacia confusa were more tolerant to low-phosphorus environment than Casuarina equisetifolia, and there was a difference in the optimum phosphorus concentration between the two. When the phosphorus concentration was 0.1 mmol·L^-1, the seed germination rate(49.33%), germination index(23.12%)and vitality index(0.093)of Casuarina equisetifolia, as well as the biomass of root, stem and leaf, all reached the maximum. In the 5 mmol·L^-1 treatment, the maximums of germination rate(81.11%), germination potential(62.22%), gemination index(38.23), vitality index(5.07), plant height(54.48 mm)and root length(37.16 mm)of Acacia confusa seeds all appeared, while their germination was inhibited in the treatment of 10 mmol·L^-1. Therefore, when sowing the seed of coastal defense forest or planting its seedling, the sowing or planting mode must be selected according to the soil salt and phosphorus contents.