水培条件下pH值对柳枝稷幼苗生长发育的影响

Effect of the pH value on switchgrass seedling growth and development in hydroponics

土壤的p H值是限制植物生长发育的一个关键因素。柳枝稷是一种可作为牧草,水土保持的多年生C4能源植物。试验在水培条件下,利用裂区试验设计,以柳枝稷品种(系)为主区,水培液p H值为副区,对反映柳枝稷幼苗生长发育状况的指标进行统计分析。结果显示,随水培液p H值的酸碱强度增大,柳枝稷不同品种(系)幼苗的分蘖数、株高、苗鲜重、根冠比、根系活力以及净光合速率都极显著降低(P<0.01),而幼苗保护酶活性以及丙二醛(MDA)含量则极显著升高(P<0.01)。尤其是当PH值低于5.0时,幼苗的受到的胁迫更为明显,幼苗超氧化物歧化酶(SOD)和过氧化物酶(POD)活性反而急剧下降。与酸胁迫(p H值<7.0)相比,柳枝稷对碱胁迫(p H值>7.0)的适应能力更强,其中以西稷2号的抗逆性表现最好。因此应用柳枝稷在边际土壤地区推广种植时,要尽量避免强酸性土壤(p H值<5.0),且选用西稷2号品系较为适宜。

With increasing societal and industrial development, soil pollution has become an increasingly serious environmental problem, and hinders the sustainable development of agriculture, especially in acidic and alkaline soils. It is well known that soil pH is a key limiting factor for plant survival and regional adaptation. Planting suitable acid- and alkali- proof plants in these types of soils was the primary focus of the present study. Switchgrass （ Panicum virgatum L. ） belongs to the family Poaceae, and is a warm season C4 perennial grass. It is a highly versatile grass used for soil and water conservation, livestock production, and biomass production as an alternative energy source. As a valuable crop, switchgrass has received much attention worldwide since the 1980s, and was introduced in China approximately ten years ago. However, the lack of water and food security is a global problem, with making its use unrealistic. Fortunately, there are a plenty of switchgrass competing with food crops for limited resources, marginal soils available on which to grow switchgrass, making its use both practical and valuable. In addition, several studies have shown that switchgrass has strong stress tolerance, including drought appropriate explore the switchgrass , salinity, leanness, acid, and alkali resistance. It is generally recognized that the range of soil pH for the growth of switchgrass is 4.9 to 7.6, but there have been no detailed reports on its acid and alkali resistance. To acid and alkMi resistance of switchgrass at the seedling stage, which is an important stage for the adaptability of to harsh environments, switchgrass seedling growth and development, in addition to net photosynthetic rate （Pn） and Swit , were studied under different pH conditions using the split-unit design in hydroponics. Switchgrass varieties ＇ Xiji 1 ＇ Xiji 2＇ were bred using the American variety ＇ Alamo, ＇ while ＇ Xiji 3＇ was bred using the American variety ＇ Natural chgrass.＇ Both Americma varieties were used as the main factors, while different pH[ 3.5, 5, 7 （ Control check, CK）, 9, and 11 ] were used as the deputy factors. The results revealed that switchgrass seedling tiller number, seedling plant height, seedling fresh weight, seedling root-shoot ratio, seedling root activity, and seedling net photosynthetic rate were sharply reduced, and that seedling protective enzyme activity and MDA （malondialdehyde） content noticeably increased as acid and alkali stress increased （ P〈0.01 ）. In particular, when the pH of the hydroponic solution was less than 5, the effect of stress on switchgrass seedlings was more noticeable because seedling SOD （superoxide dismutase ） and POD （peroxidase） activity suddenly showed a sharp decline, seedling growth and development were inhibited, and death was recorded in some instances. The effects of acid and alkali stress on seedling growth differed with switchgrass variety. Compared with acidic hydroponic conditions （pH〈7.0）, the seedlings of all switchgrass varieties became well adapted to the alkaline hydroponic conditions （ pH 〉 7.0 ） ; ＇ Xiji 2＇ was the most resistant of all switchgrass varieties. Therefore, commercial switchgrass varieties should not be planted in marginal soils that are strongly acidic soil （pH〈5.0）, with ＇Xiji 2＇ representing the optimal variety for planting switchgrass on marginal soils.