Response of Rice Seedlings to Copper Toxicity and Acidity

Metal toxicity and soil acidity affect plant growth. A hydroponic experiment was conducted to simulate effects of pH and copper concentration [Cu] on early growth and biomass production of high-yielding rice seedlings (Oryza sativa L. cv. ‘NIAB 6’). The rice seedlings were allowed to grow in Yoshida nutrient solution with 1 (control), 8, 16, and 32 μM Cu at buffered pH levels of 4.5, 5.0, and 5.5, respectively. Shoot and root growth, leaf chlorophyll content, and root lipid peroxidation and K⁺ leakage of 15-day-old rice seedlings were determined. Results show that [Cu] had significant adverse effects on rice seedlings. Shoot height and root length were reduced by 18%–60% and 7%–69%, respectively, compared with the control, and shoot and root weight decreased by 26%–56%, and 25%, respectively, in response to progressive increases in [Cu]. Similarly, leaf chlorophyll content decreased by 150%–245% compared with the control treatment. Rice seedling roots suffered from significant increases in lipid peroxidation followed by K⁺ leakage (> 8–23 times) in response to increasing [Cu]. Averaged across [Cu], seedling growth and biomass were greater at pH 5.5 than at other pH treatments. In some instances, increasing pH minimized the adverse effects of Cu at low concentrations on rice seedlings.     

RESPONSES OF WHEAT PLANTS IN TERMS OF SOIL WATER CONTENT,BULK DENSITY,SALINITY, AND ROOT GROWTH UNDER DIFFERENT PLANTING SYSTEMS AND VARIOUS IRRIGATION FREQUENCIES

The effects of irrigation water rates and seed bed shapes on changes in soil water and salinity status, bulk density, root growth and dry matter (DM) weights of wheat plants (Triticum aestivum L.) were investigated with a split plot design in a field trial in Zahak Agricultural Research Station in Sistan, Iran in 2005. Irrigation intervals after 80 and 160 mm evaporation from class A evaporation pan were used as main plot. Flat surface, single, triple, and six-row beds with a 20 cm row space were used as subplots. Each treatment was replicated four times. Volumetric soil water content and soil electrical conductivity (EC) were measured using Time Domain Reflectometry (TDR) at 0 —20, 20 —40 and 40 —60 cm depths at nine different times during the growing season. Soil water contents were also measured at 0 —10 and 10 —20 cm depths using standard sampling rings at four different times. The three and six-row beds increased the EC of the saturated paste extract with the more frequent irrigation intervals in this coarse textured soil. Soil water content, DM, and root density were always greater with the more frequent irrigations (shorter irrigation intervals). Root density was greatest in 0 —20 cm depth with the single row bed treatment. Grain yield and root density were greatest with single row bed treatment due to the bed shape at the root development stage (possibly due to a reduced mechanical resistance). A greater soil water content by the short irrigation interval increased grain yield and root density via reducing mechanical resistance. With the loamy sand, bulk density and mechanical resistance increased rapidly after cultivation. Bed shape at root development stage might have enhanced root growth and the crop yields. Apparently, mechanical resistance was the most limiting factor with these loamy sand soils than salinity.     

GENOTYPIC DIFFERENCES IN ROOT MORPHOLOGY AND PHOSPHORUS UPTAKE KINETICS IN BRASSICA NAPUS UNDER LOW PHOSPHORUS SUPPLY

Application of phosphorus (P) fertilizer is important in crop production because of the low bioavailability of phosphorus to plants in both acidic and calcareous soils. Although rapeseed (Brassica napus) is generally sensitive to P deficiency, different cultivars differ widely in this respect. Differences in P uptake and utilization between two rapeseed cultivars, one P-efficient (‘97081’) and one P-inefficient (‘97009’), were evaluated in solution culture by studying the changes in root morphology and parameters of P uptake kinetics in response to low-P stress. The P-efficient cultivar had lower Km and Cmin values and higher Vmax and developed longer and denser lateral root hair with greater number of root tips and branches under low-P stress, which resulted in a better developed root system and more efficient uptake of P. That, in turn, led to higher concentration and accumulation of P in the plants, culminating in higher biomass production. However, P utilization efficiency (biomass production per unit P accumulated in plant) of the P-efficient ‘97081’ was lower than that of ‘97009’ when P was deficient. These results suggest that P efficiency in rapeseed is due to a better developed root system as well as efficient uptake of P.     

Mycorrhizal inoculation enhances growth and nutrition of cotton plant

Arbuscular Mycorrhizae Fungi (AMF) inoculations may improve growth and nutrient uptake of cotton (Gossypium hirsutum L.) plant. Although the importance of mycorrhizal symbioses for growth and nutrient acquisition of cotton plant is known, less is known about mycorrhizal dependency on P and Zn nutrition under low Zn fertile soil conditions. A greenhouse experiment was conducted to investigate the effect of different of P and Zn fertilizer addition on cotton plant growth as well as Zn and P uptake. Sterilized and non-sterilized low Zn fertile Konya series soil was treated with different levels of P and Zn. Soils were inoculated with two mycorrhizae species like Funneliformis mosseae and Claroideoglomus etunicatum after sterilization. Results showed that mycorrhizal inoculation on plant growth and nutrient uptake has significant effect when soil was sterilized. Cl. etunicatum mycorrhizae species has greater effect than Fu. mosseae mycorrhizae species. Root colonization increased 23–65% due to mycorrhizal amendment. The shoot: root ratio increased by 13 and 22% for non-sterile and sterile condition respectively in mycorrhiza amended soil. Mycorrhizal dependency varies 1–55% and 3–64% for non-sterile and sterile soil respectively on mycorrhizae, P and Zn amended soil. Mycorrhizal dependency analysis showed that cotton plant in both sterile and non-sterile soil conditions depends on mycorrhizae species, P nutrition, however is less depend on Zn nutrition. This study concluded that the inoculation of cotton plant with selected mycorrhizae is necessary under both sterile and non-sterile soil conditions.     

发芽绿豆苗的生理指标和抗氧化特性对邻苯二甲酸酯的响应特征

Single phytotoxicity of two representative phthalate esters （PAEs）, di-n-butyl phthalate （DnBP） and bis（2-ethylhexyl） phthalate （DEHP）, was tested in mung bean （Vigna radiata） seedlings germinated for 72 h in soils spiked with varying concentrations （0-500 mg kg-1 soil） of DnBP or DEHP. PAEs added at up to 500 mg kg-1 soil exerted no significant effect on germination but both pollutants significantly inhibited root elongation （P 〈 0.01）; DEHP inhibited shoot elongation （P 〈 0.01） and DnBP depressed biomass on a fresh weight basis （P 〈 0.05）. Seedling shoot and root malondialdehyde （MDA） Contents tended to be stimulated by DnBP but inhibited by DEHP. However, increases in superoxide dismutase, peroxidase, ascorbate peroxidase and polyphenol oxidase activities, as well as glutathione （GSH） content, were induced at higher concentrations （e.g., 20 mg kg-1） of both compounds. Accumulation of proline in both roots and shoots and the storage compounds, such as free amino acids and total soluble sugars, in whole plant was induced under the stress exerted by both PAEs. The general responses of mung bean seedlings indicated higher toxicity of DnBP than DEHP on primary growth, during which root elongation was a more responsive index. MDA and GSH were more sensitive parameters in the roots than in the shoots and they might be recommended as physiologically sensitive parameters to assess the toxicity of PAE compounds in soils in future long-term studies.     

基于电阻抗成像的植物单根断层图像重建

为了实现植物根系结构形态的原位检测,植物根系单根的断层图像重建研究非常必要。该文应用动态电阻抗成像技术对土壤-树根模拟系统进行了图像重建,对重建图像进行二值化处理并求出树根在该系统中的位置坐标、面积和形状,并以树根的位置坐标、面积及形状的相对偏差为指标,分析了图像重建算法、土壤含水率2个因素对成像质量的影响。结果表明：电阻抗成像技术能够实现树木单根断层图像重建;将重建图像进行二值化处理,所得图像更加直观,便于定量评价成像质量;基于Newton单步残差正则化的一步牛顿误差重构（Newton's one-step error reconsruction,NOSER）算法,比基于全变差正则化的主双-内点模式（primal dual-interior point method,PD-IPM）算法的成像质量好;土壤含水率越高成像质量越好。该研究为基于电阻抗成像技术的植物根系结构形态的图像重建提供参考。     

水稻穴播同步侧位深施肥技术试验研究

根据水稻种植的农艺要求,在同步开沟起垄水稻精量穴播技术的基础上进一步提出了一种水稻穴播同步侧位深施肥技术。调查了在不同种植方式条件下不同品种的水稻根系在稻田中的分布情况,根据根系的分布情况研究了深施肥技术参数,确定了深施肥深度以不超过10 cm为宜,研究了培杂泰丰、玉香油占2种品种水稻施入0~5 cm土层与5~10 cm土层中的肥料比例关系。试验结果表明华南农业大学研制的同步开沟起垄侧位深施肥水稻精量穴播机能满足水稻穴播同步侧位深施肥技术的要求,可以作为实施水稻穴播同步侧位深施肥技术的载体。生产试验表明:水稻穴播同步侧位深施肥技术具有增产、节本的效用。在同等的施肥条件下,机械播种及深施肥处理的有效穗、穗平均实粒数、结实率均高于机械播种人工撒施肥和人工撒直播人工撒施肥,增产418.5~957 kg/hm2,增幅5.86%~13.41%。该文研究可为深施肥机具的设计提供参考依据。     

根系及盐分含量对农田土壤干缩裂缝发育规律的影响

为研究不同根系含量和盐分含量土壤表面干缩裂缝的发育规律,该文提出了一套基于数字图像处理的裂缝几何参数提取方法,分析裂缝形态随含水率的变化规律。结果表明:随着含水率的降低,不同根系含量条件下裂缝面积密度和长度密度的差异显著(P0.05),裂缝发育稳定时根系含量越大,面积密度越小,长度密度越大。盐分质量分数为2.0%的土壤试样在整个干燥过程中裂缝面积密度明显比其他低盐分含量的试样高。当含水率27%时,盐分含量对土壤裂缝面积密度的影响差异明显,不同盐分含量的土壤裂缝面积密度和长度密度均差异显著(P0.05),说明盐分含量越大,稳定时土壤裂缝面积密度越大,长度密度越小。该成果对指导开裂土壤的农田灌溉具有重要的实践意义。     

后墙立体栽培草莓提高冬季日光温室内温度

在日光温室的后墙上,采用管道无土栽培方式进行蔬菜或草莓生产,可以提高温室空间利用率和作物种植量,但可能会出现因为管道和植物的挡光而减少后墙蓄热、降低冬季温室温度的问题。为此,通过冬季连续31 d的温度监测,在3种典型气象（晴天、阴天、雪天）条件下,对比分析了有后墙立体基质栽培的日光温室（solar greenhouse with equipment,ESG）和无后墙立体栽培的日光温室（solar greenhouse with no equipment,NSG）温度环境的变化。监测结果表明,ESG的月平均气温较NSG高0.84℃,其中最大日温差为2.22℃,最小日温差为0.14℃。晴天条件下,ESG的日平均冠层温度和1.5 m高度处的空气温度分别是12.72和13.04℃,NSG分别是10.68和11.04℃;ESG的冠层温度最低值是4.68℃,而NSG最低值是4.10℃。可见,ESG较NSG的气温要略高一些;阴天和雪天条件下,2种温室内的温度环境无显著差别。因此,利用日光温室后墙进行立体基质栽培草莓,不但没有降低反而提高了冬季温室内的温度,是一种可行、值得推广应用的温室高效栽培技术。     

根表功能细菌生物膜及其在土壤有机污染控制与修复中的潜在应用价值

土壤中的有机污染物可从根系进入植物体内,并可进一步通过食物链富集,从而威胁人群健康。植物根际微生物种类繁多、数量巨大,其中很多根际细菌可通过成膜作用在植物根表形成细菌生物膜,协助植物抵抗外界的不良环境或促进植物生长。有机污染物在被植物根系吸收的过程中,多需经过根表细菌生物膜这一特殊界面。综述了根际细菌在植物根表的成膜作用,以及根表功能细菌生物膜对污染物根际环境过程的影响及作用机理,分析了利用根表功能细菌生物膜调控植物吸收有机污染物的可行性,试图为防治土壤有机污染、降低作物污染风险、保障农产品安全等提供理论依据。