Changes induced by plastic film mulches on soil temperature and their relevance in growth and fruit yield of pickling cucumber

Purpose: The aim of this study was to realize whether soil mulching, with different plastic mulch colors, is a suitable practice for the culture of pickling cucumber.

Materials and Methods: The crop was cultured or not with black, silver/black, white/black, and aluminum/black plastic films, treatments were evaluated in randomized complete block design, to determine their effect on soil temperature, gas exchange, nutrient concentration, growth, and fruit yield.

Results and Conclusions: Black, silver/black, and aluminum/black plastic mulches were higher (p?≤?0.05) in plant height, leaf area, and shoot dry weight than bare soil at 15 days after sowing, whose results were similar than using white/black film. Maximum, minimum, and mean soil temperatures were higher with all plastic mulches except for aluminum/black, in which the maximum soil temperature was similar to the one in bare soil. There was no difference in net photosynthesis and there was very little difference in nutrient concentration between plants in plastic mulches and plants in bare soil; however, early and total yield showed a higher (p?≤?0.05) yield in all plastic mulches, and lower with bare soil and white/black plastic mulch. Our results confirm that soil mulching impacts the pickling cucumber yield. We suggest a carefull selection of the color plastic mulch.     

CO2浓度升高与增施钾肥对黄瓜生长的影响

采用土培和开顶箱法,研究了大气CO_2浓度升高与K肥共同作用对黄瓜生长的影响.结果表明,CO_2浓度升高和K肥浓度增大均能增加黄瓜干物质的积累,且在高CO_2浓度下.200mg/kg和300 mg/kg K肥处理时黄瓜的干物重达到最大值.大气CO_2浓度升高使得黄瓜体内的N、P、K、Na、Ca、Mg含量均降低,K肥处理对黄瓜植株内N、P、Ca、Mg含量的影响不大,但K的含量随K肥的增加而增加.在高浓度CO_2下,200mg/kg和300mg/kg K肥处理时黄瓜对N、P、K、Ca、Mg的吸收量达到最大值.可见,在未来CO_2浓度升高的环境中,更多的K肥供应能促进作物对N、P、K、Ca、Mg的吸收,使其快速高效的生长.     

铝胁迫对黄瓜种子发芽及抗氧化酶活性的影响

本试验以黄瓜品种津春2号为材料,研究了铝胁迫对黄瓜种子发芽及抗氧化酶活性的影响。结果表明,铝处理显著抑制了黄瓜种子萌发后根部的伸长,提高了根部抗坏血酸过氧化物酶（APX）、过氧化物酶（POD）、过氧化氢酶（CAT）和脱氢抗坏血酸还原酶（DHAR）活性。超氧化物歧化酶（SOD）在低浓度铝处理下活性升高,而在高浓度下降低。     

生物技术在甜瓜育种中的应用

阐述甜瓜离体培养、单倍体育种、细胞和原生质体培养及抗病毒性等方面取得的研究进展,并对甜瓜组织培养、生物技术与育种的前景作了展望。     

Variation in sugar levels and invertase activity in mature fruit representing a broad spectrum of Cucumis melo genotypes

Sugar accumulation is a very important physiological process that determines dessert-melon fruit quality. Considerable variation in the sugar content and composition in the mature flesh of Cucumis melo L. fruits was observed among 56 genotypes which represent the wide range of morphological and horticultural types found in this species. Sucrose accumulation was observed not only among 'dessert melons' of the inodorus and cantalupensis types, but also in representatives of other subgroups of C. melo, including some of the accessions from agrestis and conomon groups. Among the genotypes that accumulate sucrose, the levels of this sugar, and not of the hexoses, were correlated with the total sugar concentration. Hexose levels were correlated with total sugar levels only among low-sugar genotypes that did not accumulate sucrose. Activities of the sucrose hydrolyzing enzymes acid invertase (EC 3.2.1.26) and alkaline invertase (EC 3.2.1.27) were measured in the mature fruit flesh and the results of this survey support the hypothesis that low acid invertase activity is a prerequisite for sucrose accumulation. The sucrose accumulating, high sugar genotypes had less-acidic flesh pH values (pH> 6) than the low-sugar genotypes. The latter were characterized by a broader range of pH values, including acidic (pH< 5.5) fruit flesh.     

Synthetic Iron Chelates as Substrates of Root Ferric Chelate Reductase in Green Stressed Cucumber Plants

This work studied the behavior of different iron (Fe)-chelates as substrates of ferric chelate reductase (FCR) and their ability as Fe suppliers for mildly chlorotic plants. FCR activity and Fe concentration in xylem sap were determined in green stressed cucumber plants with different stress levels using different synthetic chelates as substrates. Both reduction and Fe concentration in the xylem sap were higher for the less-stable Fe chelates, except for Fe-EDTA, which presented a relatively low Fe concentration in sap. It was concluded that a high stability of the chelate in the nutrient solution reduces the Fe reduction, but other factors, such as the complexation of the Fe(II) by the chelating agents, should be considered when the complete process of Fe uptake is studied. The use of both indexes together, i.e., FCR determination and xylem sap concentration, is useful for understanding the Fe uptake from different Fe chelates.     

Analysis based on RAPD and ISSR Markers Reveals Closer Similarities among <Emphasis Type="Italic">Citrullus</Emphasis> and <Emphasis Type="Italic"> Cucumis</Emphasis> Species than with <Emphasis Type="Italic">Praecitrullus fistulosus</Emphasis> (Stocks) Pangalo

A cucurbit species named Praecitrullus fistulosus (Stocks) Pangalo, which thrives in India, is considered to be a distant relative of watermelon. Recent experiments indicated that it has mild resistance to whiteflies (Bemisia tabaci). However, our attempts to cross various US plant introductions (PIs) of P. fistulosus with watermelon or other Citrullus PIs have not been successful. Thus, to determine genetic relatedness among those species, phylogenetic analysis [based on simple sequence repeat (SSR)–anchored (also termed ISSR), and randomly amplified polymorphic DNA (RAPD) markers] was conducted among PIs of P. fistulosus, Citrullus lanatus var. lanatus (watermelon), C. lanatus var. citroides and the wild Citrullus colocynthis. Phylogenetic relationships were also examined with Cucumis melo (melon), Cucumis sativus (cucumber), and wild Cucumis species including C. africanus, C. metuliferus, C. anguria, C. meeusei, and C. zeyheri. Wide genetic distance exists between Citrullus and Cucumis groups (8% genetic similarity). Phylogenetic relationships among Citrullus species and subspecies are closer (25–55% genetic similarity) as compared with those among most Cucumis species (14–68% genetic similarity). P. fistulosus appeared to be distant from both Cucumis and Citrullus species (genetic similarity between P. fistulosus and Cucumis or Citrullus groups is less than 3%). Although wide genetic differences and reproductive barriers exist among cucurbit species examined in this study, they are still considered as potential germplasm source for enhancing watermelon and melon crops using traditional breeding and biotechnology procedures.     

甜瓜属野生种及其与黄瓜种间杂交后代抗根结线虫初步研究

为了鉴定甜瓜属野生种酸黄瓜 (CucumishystrixChakr.)对南方根结线虫 [Meloidogyneincognit(Kofoid&White)Chit wood]的抗性 ,进而评估抗性向酸黄瓜与栽培黄瓜种间杂种的转移 ,选用了酸黄瓜、 4个栽培黄瓜材料、两种倍性水平的 3个正反交杂种F1和 1个回交后代作为试材 ,在温室中进行抗性鉴定和筛选。结果表明 ,酸黄瓜对南方根结线虫具有高度抗性 ,而 4个栽培黄瓜材料均为高度敏感。酸黄瓜平均每株根系形成约 3个根结 ,栽培黄瓜材料每株根系的根结数超过 10 0个。酸黄瓜通过与栽培黄瓜的正反交 ,其抗性已被部分转移到杂种之中。当杂种作为供体亲本与栽培黄瓜进行回交时 ,抗性又被进一步转移到回交一代 (BCF1)中     

甜瓜小拱棚栽培品种比较试验

对6个厚皮甜瓜品种在拱棚栽培条件下的适应性和产量、品质表现进行了比较研究。结果表明，古拉巴和玉金香2个品种兼具优质、丰产、抗病、抗逆性强等优良性状，具有拱棚种植的开发潜力，可作主栽品种推广。伊丽莎白是仅次于古拉巴和玉金香的早熟优良品种，可作为拱棚栽培的搭配品种使用。     

土壤水分对日光温室黄瓜生长发育及光合特性的影响

黄瓜是需水量大且对水分敏感的蔬菜作物之一,水分管理的好坏是实现日光温室黄瓜高产高效的关键。为此,本文研究了不同土壤水分条件对日光温室黄瓜形态指标及光合特性的影响,结果如下：① 保持80%~90%的土壤相对含水量(T3),植株生长发育良好,根冠比适宜,生物量、单瓜重及产量高,畸形率低,均显著高于低水处理(T1: 60%~70%, T2: 70%~80%),而与高水处理(T4: 90%~100%)差异不显著;低于此含水量(如T1、T2),生长缓慢,植株矮小,瓜条畸形率高,单瓜重小,产量低;高于此含水量(如T4),则植株徒长,水分利用效率低,同时也为病虫害发生提供了适宜的环境条件。② 从光合特性及其日变化来看,净光合速率、蒸腾速率、气孔导度及光能利用率均随土壤含水量的增加而增加,而叶片水分利用效率随土壤含水量的增加而呈降低趋势;T2、T3与T4的净光合速率、蒸腾速率、气孔导度及光能利用率日变化呈双峰曲线,第一峰出现在11：00时,第二峰出现在15：00时;而T1则呈单峰曲线,峰值出现在10：00时,比T2、T3、T4提前1小时,水分利用效率日变化呈先升后降的趋势。