塔克拉玛干沙漠南缘玉米对不同荒漠化环境的生理生态响应

为了研究玉米对不同荒漠化环境的适应性,以塔克拉玛干沙漠南缘策勒绿洲外围不同荒漠化程度下生长的玉米为试验材料,大田试验为手段,布置3个胁迫水平(轻度荒漠化、中度荒漠化、重度荒漠化),研究了玉米的土壤含水率、植株高度、生物量分配、脯氨酸(Proline)、丙二醛(MDA)、可溶性糖(Sugar)、叶绿素(Chl)、叶绿素荧光参数、比叶面积(SLA)等在不同胁迫梯度下的变化特征。结果显示:随着荒漠化程度的加剧,玉米生物量、脯氨酸、丙二醛、叶绿素、类胡萝卜素、Chl a/b、叶绿素荧光参数都有不同幅度的下降;中度荒漠化可溶性糖含量最低,重度最高,轻度介于两者之间;Car/Chl、比叶面积和地下生物量占总生物量的比重都随荒漠化程度的加剧,呈增加趋势。结果表明,荒漠化环境明显对玉米的生长产生了抑制作用;随着荒漠化程度的加剧,玉米植株的光合色素含量降低,PSⅡ受到影响,从而影响植株的光合作用,使玉米物质的积累受到影响;玉米自身通过在营养器官分配更多的能量和积累调控物质,并且在形态结构上也会发生某些改变以适应更恶劣的环境。随着胁迫程度的加剧,对其生长抑制愈严重。

Physiological and ecological responses of maize to different severities of desertification in the Southern Taklamakan desert

Qira Oasis is located on the southern fringe of the Taklamakan Desert, the most arid region in northwest China, where the mean annual precipitation is less than 40 mm but the evaporation can be as high as 2600 mm per year. Implementation of agriculture at Qira Oasis is constrained by multiple environmental factors, e.g. strong sunlight, high temperature, drought, and low soil fertility. As a C4 plant, maize shows a high photosynthetic rate, better adaptability to salinity and desertification, and stronger competitiveness. To research the adaptability of maize to different severities of desertification, field experiments were performed using Shenyu 2000 ( a maize cultivated by Shenyang academy of agriculture sciences) growing in a desertification gradient outside of Qira Oasis and subjected the experimental plots to three stress treatments (mild, moderate, and severe desertification, designated D1, D2, and D3, respectively). D1 was located in marginal farmland in the oasis, D2 in the transitional zone between farmland and desert, and D3 on the desert edge of the transition zone. Each treatment consisted of three experimental plots, arranged in an L arrangement, comprising an area 20 m long and 15 m wide. The distance between each site was about 1 km, and the moderate and severe desertification sites were separated by a 1-meter-wide shrub forest belt of Calligonum mongolicum. The soil water content, plant height, biomass allocation, proline, malondialdehyde, soluble sugar, chlorophyll (Chl), chlorophyll fluorescence parameters, and specific leaf area of the maize plants were recorded during the pollination period. Desertification inhibited growth of the maize plants. Growth and photosynthesis parameters showed different rates of decline at different desertification severities. At D3, biomass, proline, malondialdehyde, chlorophyll, carotenoids (Car), Chl a/b, decreased 291.88, 110.38, 50.64, 218.71, 133.26, and 21.35%, respectively, and the chlorophyll fluorescence parameters Fv/Fm, Fv/Fo, and Fm/Fo also decreased by 10.01, 34.37, and 23.36%, respectively, compared with those at D1. The soluble sugar content was lowest in the moderate desertification treatment and highest in the severe desertification condition; at D2, it decreased 8.28%, compared with D3. The Car:Chl ratio, specific leaf area and the ratio between underground biomass and total biomass increased with increasing desertification severity. Compared with D1, these parameters increased 36.68%, 12.86% and 53.04%, respectively. The results indicated that implementation of agriculture at Qira Oasis is a comprehensive and complex environment. For improved adaptation to desertification, maize plants allocate greater energy to vegetative organs, and also alter their vegetative morphology to adapt to an increasingly severe environment. Although maize plants can adapt to desertification conditions by regulation of metabolic processes and metabolite accumulation, these are also primary factors that limit their normal growth and physiology. The effect of different desertification stress gradients on maize mainly reflects the light intensity and pigment and the structure of PSII, which affect photosynthesis and decrease biomass accumulation. The growth of maize is significantly limited by desertification as the level of stress increases.