Flavones and flavonoids are known to have potent antioxidant activity due to intracellular free radical scavenging capacities. Flavonoids are found ubiquitously in plants as a member of polyphenolic compounds which share diverse chemical structure and properties. Quercetin is among the most efficient antioxidants of the flavonoids. The antioxidant property of quercetin has been highlighted in this review. These compounds have pivotal role in treatment of diabetes, cancers and some cardiovascular diseases.

In recent years, there has been an increasing interest in consumption of red fruits and vegetables due to its rich dietary sources of antioxidant, phenolics and anthocyanins. In this study, phytochemical and antioxidant properties of green and red lettuce cultivars were studied. Particularly, the effect of leaf position on these properties was compared. Eight conventionally grown cultivars of lettuce (Lactuca sativa L.), with four green (Fonseca, Freckles, Krizet and Filipus) and four red (Versai, Nation, Paradai and Cherokee) cultivars were studied. Their leaves were divided into three groups; outer, middle and inner part. Total antioxidant capacity (TAC) of each group of leaves was assessed by both trolox-equivalent antioxidant capacity (TEAC), and the ferric reducing antioxidant power (FRAP) assay. Leaf color, total soluble solids, total phenolics (TP), total anthocyanin (TACY), chlorophyll a and b were determined. The results demonstrated that outer leaves have the highest phytonutrient content and antioxidant properties. Outer leaves exhibited significantly higher TP and TAC than middle and inner leaves in both red and green color lettuce. The average TP content of red lettuce were 845, 297 and 195 μg gallic acid equivalent per gram fresh weight in the outer, middle and inner leaves, respectively. Also TAC of outer leaves was significantly higher than middle and inner leaves in both red and green color lettuce. The magnitude of difference between red and green cultivars was significant as determined by both TEAC and FRAP methods.

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Tuberization in potato is known to be under complex biochemical control involving hormones. A number of studies have provided evidence for a critical role of GA in tuberization. There is also evidence that GA in plants can be modulated by a Ca/calmodulin pathway. The purpose of the present study was to determine the influence of supplemental Ca fertilization on tuber size and tuber number. Plantlets of Solanum tuberosum `Russet Burbank' raised in tissue culture were planted in 20-L pots filled with sandy loam field soil with the pH of 6.9 and exchangeable soil Ca level of 350 ppm. All treatments received the same total amount of N (equivalent to the rate of 280 kg·ha-1). Four treatments were evaluated: nonsplit N (from ammonium nitrate), split N (from ammonium nitrate), split N+Ca (from calcium nitrate), split N+Ca (50% N from urea, 50% N from ammonium nitrate and Ca from calcium chloride). The total Ca was applied at the rate equivalent to 168 kg·ha-1 on a split schedule (equally split at four, six, eight and ten weeks after planting). Four months after planting tubers were harvested and evaluated. As expected tuber tissue Ca was increased by Ca application from 144 to 245 μg·g-1. In general, the two Ca treatments had significantly lower tuber number per plant as compared to the nonsplit and split N treatments. A plot of mean tuber Ca and tuber number for individual plants showed a significant negative relationship. Both Ca treatments produced tubers with higher mean tuber weight compared to nonsplit N. This increase in tuber size with Ca application was not apparent when compared with split N treatment. These results show that Ca application to soil can decrease tuber number suggesting that soil Ca may influence tuberization in potato.