Field experiments were conducted to study genotypic variation for potassium uptake and utilization efficiency in sweet potato for 2 years. In 1997, a field experiment was conducted using 84 genotypes under no potassium fertilization. In 1998, two field experiments were carried out. In experiment I, eight good genotypes evaluated from the previous experiment were tested at two K application levels: 0 and 270 kg ha-1 of K2SO4. In experiment II, three special varieties with respect to pigment content were tested at five K levels from 0 to 600 kg ha-1. A split-plot design with three replications was used. Variation existed among genotypes in K concentration, accumulation and potassium efficiency ratio(KER) in the field. Among various plant parts, petiole contained the highest K concentration and storage roots had the highest K accumulation at maturity. These changed considerably with genotype and K level. KER had significant positive correlation with root weight per plant, root: top ratio and harvest index (HI); and significantly negative correlation with K concentration and accumulation in the roots or whole plant at maturity. Based on KER, genotypes were identified as efficient and inefficient in potassium utilization. Yield increased generally in all genotypes with K application. The increase, however, varied among different genotypes. It was also found from this study that the fertilizer level that gave the highest yield was K2 which is 300 kg ha-1 of K2SO4. The yield increase as a result of K application was mainly due to the increase in root: top ratio which led to greater amount of photosynthate translocation to the storage roots causing their increase in size. Most of the quality parameters tested increased with increasing levels of K nutrition. Root dry matter(%), Brix (%), carotene content, anthocyanin content increased with K application. The extent of increase, however, differed with genotypes. Protein cntent generally tended to reduce with increase in K level. The degree of reduction also varied with genotypes.

采用差示扫描量热分析仪（DSC）和淀粉粘度速测仪（RVA）分析了3 个甘薯品种（系）在块根发育过程中淀粉糊化特性的变化。结果表明，随甘薯生育期的延长，3 个品种的淀粉率都呈下降趋势，但直链淀粉率的变化则因品种而异。早期收获，徐薯18 和浙大9201 的直链淀粉率表现较高，而浙3449 则较低。随生育期延长，DSC糊化峰向低温方向移动，且峰宽增大、峰逐渐消失，其糊化温度和热焓变化也随之递减，而RVA 的最高粘度则呈现递增趋势。相关分析发现，甘薯直链淀粉含量与各糊化特性参数间存在一定相关性，但这种相关性的大小又受到品种制约。

用电感耦合等离子体原子发射光谱仪( ICP - OES) 测定了甘薯21个品种(系) 5个产地200多份样品中的铁、锌、钙、硒四种有益矿物质营养元素含量。结果表明:铁、锌、钙和硒四种矿物成分含量存在明显的基因型差异,其平均含量分别为38.97、49.02、889.70、0.1472mg/kg(干基) ,相应的变幅依次为1.97～167.86、11.68～245.40、37.63～1925.6 和0.01～0.51 mg/kg (干基) 。不同肉色甘薯铁、锌、钙和硒含量差异不显著;除铁外,锌、钙和硒含量产地间均存在显著差异。

The effects of zucchini yellow mosaic virus (ZYMV) infection and pretreatments with salicylic acid (SA) on biomass accumulation of pumpkin (Cucurbita pepo cv. Eskandarani) were investigated. The response of photosynthesis, transpiration and the activities of antioxidant enzymes in leaves was also considered. Significant reductions in growth parameters (i.e. leaf area, biomass and shoot height), photosynthesis and chlorophyll a and b content were detected in ZYMV-infected leaves in comparison to healthy controls. Antioxidant enzyme activities were increased up to 3-fold for peroxidase (POD), 2-fold for ascorbate peroxidase (APX) and catalase (CAT) activities and 1.3-fold for SOD activity by virus infection. ZYMV infection also caused increases in H2O2 and malondialdehyde (MDA) contents. These results suggest that ZYMV infection causes oxidative stress in pumpkin leaves leading to the development of epidemiological symptoms. Interestingly, spraying pumpkin leaves with SA led to recovery from the undesirable effects of ZYMV infection. Leaves treated with 100 mM SA three days before inoculation had the appearance of healthy leaves. No distinct disease symptoms were observed on the leaves treated with 100 mM SA followed by inoculation with ZYMV. In non-infected plants, SA application increased activities of POD and superoxide dismutase (SOD) and inhibited APX and CAT activities. In contrast, SA treatment followed by ZYMV inoculation stimulated SOD activity and inhibited activities of POD, APX and CAT. In addition, MDA displayed an inverse relation, indicating inhibition of lipid peroxidation in cells under SA treatment. It is suggested that the role of SA in inducing plant defense mechanisms against ZYMV infection might have occurred through the SA-antioxidant system. Such interference might occur through inhibition or activation of some antioxidant enzymes, reduction of lipid peroxidation and induction of H2O2 accumulation following SA application.