The positive function of selenium supplementation on reducing nitrate accumulation in hydroponic lettuce (Lactuca sativa L.)

High nitrate(NO_3~- ) in vegetables, especially in leaf vegetables poses threaten to human health. Selenium(Se) is an important element for maintaining human health, and exogenous Se application during vegetable and crop production is an effective way to prevent Se deficiency in human bodies. Exogenous Se shows positive function on plant growth and nutrition uptake under abiotic and/or biotic stresses. However, the influence of exogenous Se on NO_3~- accumulation in hydroponic vegetables is still not clear. In the present study, hydroponic lettuce plants were subjected to six different concentrations(0, 0.1, 0.5, 5, 10 and 50 μmol L–1) of Se as Na2 Se O3. The effects of Se on NO_3~- content, plant growth, and photosynthetic capacity of lettuce(Lactuca sativa L.) were investigated. The results showed that exogenous Se positively decreased NO_3~- content and this effect was concentration-dependent. The lowest NO_3~- content was obtained under 0.5 μmol L–1 Se treatment. The application of Se enhanced photosynthetic capacity by increasing the photosynthesis rate(Pn), stomatal conductance(Cs) and the transpiration efficiency(Tr) of lettuce. The transportation and assimilation of NO_3~- and activities of nitrogen metabolism enzymes in lettuce were also analysed. The NO_3~- efflux in the lettuce roots was markedly increased, but the efflux of NO_3~- from the root to the shoot was decreased after treated with exogenous Se. Moreover, Se application stimulated NO_3~- assimilation by enhancing nitrate reductase(NR), nitrite reductase(Ni R), glutamine synthetase(GS) and glutamate synthase enzyme(GOGAT) activities. These results provide direct evidence that exogenous Se shows positive function on decreasing NO_3~- accumulation via regulating the transport and enhancing activities of nitrogen metabolism enzyme in lettuce. We suggested that 0.5 μmol L–1 Se can be used to reduce NO_3~- content and increase hydroponic lettuce yield.     

Multilayer Perceptron Neural Network Approach to Estimate Chlorophyll Concentration Index of Lettuce (Lactuca sativa L.)

Nitrogen is an essential nutrient for greenhouse-grown lettuce (Lactuca sativa L.); however, excessive nutrient availability causes disease and detrimental effects on the leaf and root development. In this study, nitrogen content of the lettuce leaves was estimated by determining the chlorophyll concentrations of the leaves using image processing technique. The Hoagland solution was used as a fertilizer in five different doses (control, quarter of the solution, half of the solution, standard solution, and two times more of the solution). Multilayer perceptron neural network (MLPNN) model was developed based on the red, green, and blue components of the color image captured to estimate chlorophyll content and chlorophyll concentration index (SPAD values). According to the obtained results, the MLPNN model was capable of estimating the lettuce leaf chlorophyll content with a reasonable accuracy. The coefficient of determination was 0.98, and mean square error was 0.006 in validation process.     

越冬圆叶莴苣品种比较试验

为筛选出适合武汉市越冬栽培的莴苣品种,对4个越冬圆叶品种进行品种比较试验,结果表明,华笋在株高、叶片数、笋茎长、茎粗、抗病性等方面优势明显;熟性上,华笋比对照品种雪里松晚7 d左右;净菜率上,华笋为62.2%,雪里松为66.7%;产量方面,华笋比雪里松显著增产23.0%;耐寒性和抗病性方面,华笋均表现最好,华笋的冻害指数和感病指数分别为40.8和62.0,雪里松为51.0和77.5,差异均达显著性水平;其他2个品种的综合性状表现均较华笋差。因此,华笋在越冬品种栽培上优势较大,具有极大的推广价值。     

营养生长期长短对直立生菜生长、产量和品质的影响

研究了直立生菜营养生长期长短对其生长、产量和品质的影响,结果表明:直立生菜的株高、叶片数均与定植时间具有直线线性正相关:直立生菜的产量与采收时间相天,采收时间延长,产量随之增加;定植51 d后,老叶的水分、维生素C和粗蛋白含量均高于嫩叶,嫩叶的还原糖、可溶性固形物和硝酸盐含量均高于老叶,老叶和嫩叶的品质虽有一定的差别,但老叶仍具有较高的食用价值.     

局部控制地下浸润灌溉对叶用莴苣生长及水分利用效率的影响

通过两年的盆栽试验,对比研究了局部控制地下浸润灌溉和地表滴灌对作物根区土壤水分动态及叶用莴苣的光合速率、蒸腾速率、水分利用效率、产量和品质的影响。结果表明,局部控制地下浸润灌溉的蒸发量明显小于地表滴灌处理,莴苣产量高于地表滴灌处理;水分利用效率是局部控制地下浸润灌溉处理最高,达到了42.42 kg/m3,地表滴灌仅为15.14 kg/m3;各处理光合速率和蒸腾速率日变化均呈"双峰"曲线,且呈处理1>处理2>处理3>处理4的趋势;局部控制地下浸润灌溉处理的根冠比较高,最大值达0.187,而地表滴灌处理的根冠比仅为0.071;局部控制地下浸润灌溉中莴苣的Vc含量达到了14.62 mg/100g,而地表滴灌处理仅为12.82mg/100g。说明局部控制地下浸润灌溉能有效改善莴苣的光合产物分配,调整根冠比关系,提高莴苣的水分利用效率,使作物产量与品质得到统一。     

叶面喷施氯化钙对海南高温季节水培生菜生长生理的影响

为了探索高温水培环境下叶面喷施氯化钙对生菜生长生理的影响,以辛普森精英散叶生菜为材料,在35℃/25℃(昼/夜)下设置4个氯化钙浓度1、3、5、7 mmol·L-1处理,以清水为对照.结果表明,与对照相比,5 mmol·L-1氯化钙处理生菜最大叶宽、地上部鲜质量、地下部鲜质量和抗氧化酶活性均显著提高,丙二醛含量和叶片相...     

六个油麦菜新品种引种试验

以‘极品’油麦菜、‘纯香’油麦菜、‘蓝斯Lance’、‘泰国四季香’油麦菜、‘泰国香’油麦菜及‘板叶香’油麦菜为试材,对其生育期、品质、产量等进行比较分析。结果表明:‘极品’油麦菜长势强、品质好,产量高,667m2产量达2 408.7kg,是目前最适合黔西南州的新品种。     

日光温室不同种植位置温光变化及对结球生菜产量的影响

研究旨在探索基于日光温室条件下科学高效的种植模式,为实现日光温室蔬菜科学化种植、统一化管理、标准化生产奠定理论基础。通过监测分析温室不同种植位置的气温、地温、湿度以及光照强度,研究不同种植位置的温湿度及光照变化规律。同时,选取8个结球生菜品种,分畦测定不同品种生菜的产量,研究日光温室不同种植位置对结球生菜产量的影响。结果表明,温室不同种植位置的温度、湿度、光照强度均存在较大差异,气温、地温由南向北逐渐升高,光照强度先升高后降低。由于温光条件的差异导致结球生菜南北两边的长势都不均匀,不同品种生菜产量由南向北呈现出较为一致的规律性,即北边产量高于南边,靠近棚边最南边的位置与其他区域生菜产量存在显著差异。试验研究温室不同种植位置的温光等环境条件变化规律,为温室蔬菜科学化种植提供了理论依据。     

品种和播种期对秋莴笋先期抽笋率和产量的影响

对７ 个秋莴笋品种的４ 个播种期进行了比较试验,结果表明先期抽笋与品种和播种期密切相关。阔圆叶品种最不易先期抽笋,长圆叶品种次之,尖叶品种最容易先期抽笋。秋莴笋合适的播种期在８ 月中旬,合适的品种也比较多,若播种期提前到７ 月中下旬,只能选用圆叶品种。     

塑料大棚中不同灌水量下限对生菜生长和生理特性的影响

以两个散叶生菜品种弘农和绿领为材料,研究了塑料大棚栽培条件下不同田间持水量处理(70%～90%、60%～90%、50%～90%、40%～90%)对生菜产量、品质、叶绿素荧光参数和保护酶活性的影响.结果表明,以田间持水量的70%作为灌水量下限条件下生菜地上部鲜质量、叶片含水率、叶片数、叶面积均最大.随着灌水量下限的降低,生菜可溶性糖、可溶性蛋白含最逐渐增加,灌水量下限为田间持水量50%处理下的维牛素C含量显著岛于其他三个灌水量下限处理.对叶绿素荧光参数的分析表明,随着灌水量下限的降低,Fv/Fm(光系统Ⅱ最大光化学效率)、qP(光化学淬灭)、ΦpsⅡ(光系统Ⅱ电予传递量子效率)逐渐减小,而qN(非光化学淬灭)则逐渐增加.SOD(超氧化物岐化酶)和CAT(过氧化氢酶)活性,MDA(丙二醛)和Pro(脯氨酸)含量均随着灌水量下限的降低而逐渐增加.本试验的结果表明,70%灌水量下限处理下生菜的产量最高,综合不同灌水量下限处理对产量和品质的影响,60%的灌水量下限处理是最适合生菜生长的灌水处理.