A rapid predictive method based on near-infrared reflectance (NIR) spectroscopy (NIRS) was developed to measure sweetpotato starch physiochemical quality and pasting properties. The starch samples were scanned by NIRS and analyzed for quality properties by reference methods, respectively. Results of statistical modeling indicated that NIRS was reasonably accurate in predicting amylase content (AC), amylose percent (AP), total starch content (TSC), protein content (PRC), phosphorus content (PHC), solubility (SOL), swelling power (SP), average granule diameter (AGD), big granule percent (BGP), small granule percent (SGP), crystallinity (CRY), peak viscosity (PKV), hot paste viscosity (HPV), setback (SB), and pasting temperature (Ptemp) with high coefficients of determination (RSQ = 0.85–0.92) and relatively low standard errors of prediction. The results showed that NIR analysis was sufficiently accurate and effective for rapid evaluation of starch physicochemical properties in sweetpotato. The NIR-based protocol developed in this study can be used for screening large number of starch samples in food enterprises and sweetpotato breeding programs.

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.

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.

采用扫描电镜、X-射线衍射和粘度测定等方法对甘薯、马铃薯和芋艿3种我国主要根茎作物淀粉的理化特性和糊化特性进行了研究，以便为其有效利用提供理论依据。结果表明：这3种根茎作物淀粉粒均有圆形、椭圆形和不规则多边形的形状，淀粉粒大小、分布、表面结构、晶体特性、淀粉成分和糊化特性作物间存在显著差异。而作物品种问差异较小。