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Luping Qu, Xiping Wang, Jinghua Yang, Eatherley Hood and Richard Scalzo

Seeds from five lots each of Echinacea angustifolia DC and E. pallida (Nutt.) Nutt. were germinated in a growth chamber in light (40 μmol·m-2·s-1) or darkness at 25 °C for 16 to 20 days after soaking in 1 mm ethephon or water for 10 minutes or moist stratification at 4 - 6 °C for 2 weeks. Either light or ethephon promoted seed germination of E. angustifolia and E. pallida compared with darkness in nine of ten lots. Ethephon in the dark had similar or greater germination percentages than water with light. Ethephon with light improved germination in three of ten lots compared with ethephon in the dark. The effect of cold, moist stratification compared with darkness varied by seed lot. Five lots of E. purpurea (L.) Moench were tested, however, no treatment differences were measured. The finding that ethethon promoted E. angustifolia and E. pallida seed germination in darkness could be useful in the cultivation of these two species. Chemical name used: 2-chloroethylphosphonic acid (ethephon).

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Jinghua Guo, Yan Yan, Lingdi Dong, Yonggang Jiao, Haizheng Xiong, Linqi Shi, Yu Tian, Yubo Yang and Ainong Shi

Hydroponics has been an increasingly important field of vegetable production. However, a big issue with hydroponics is that certain crops can quickly accumulate high levels of nitrate-N (NO3 ± -N) from the hydroponic system. The objective of this research was to decrease NO3 accumulation and increase the nutritional value and yield of vegetable crops using lettuce and oilseed rape as a model under hydroponic production. In this study, two technologies were applied to leafy vegetable production: 1) using supplementary lighting (blue-violet diode) by manipulating illumination and 2) removing fertilization before harvest for a short term (3 or 5 days), thus providing a practical experiment for improving yield and edible qualities of hydroponic leaf vegetable production. Illumination was applied 4 hours a day (0500–0700 hr and 1700–1900 hr) during good weather, or 12 hours a day during bad weather with insufficient natural light (<2000 lux) during the autumn and winter seasons. Results showed that the lettuce cultivar Ou-Luo and the oilseed rape cultivar Ao-Guan Pakchoi had increased yield (50.0% and 88.3%, respectively), decreased NO3 content (26.3% and 30.8%, respectively), and increased total soluble solids (24.1% and 30.6%, respectively). The 5-day fertilizer-free treatment before harvest resulted in 19.2%, 6.4%, and 16.5% yield increases; and 26.0%, 24.3%, and 47.8% NO3 decreases in oilseed rape cultivar Ao-Guan Pakchoi and lettuce cultivars Da-Su-Sheng and Ou-Luo, respectively.

Open access

Jehanzeb Khan, Yubin Yang, Qiang Fu, Weiqiang Shao, Jianke Wang, Li Shen, Yan Huai, Guy Kateta Malangisha, Abid Ali, Ahmed Mahmoud, Yi Lin, Yongyuan Ren, Jinghua Yang, Zhongyuan Hu and Mingfang Zhang

Watermelon (Citrullus lanatus) is an important horticultural crop that is sensitive to heavy metals such as lead (Pb) in polluted water or soil. However, there are no available data regarding Pb tolerance phenotyping in watermelon. Watermelon seedlings were exposed to various Pb doses (0, 20, 40, 60, 80 µm·L–1 Pb) for 14 days, after which 20 µm Pb was identified as the optimal treatment for lead tolerance analysis in watermelon because it caused significant symptoms (leaf chlorosis, stubby and yellow roots) but little damage to seedlings. Subsequently, the Pb responses were analyzed in eight watermelon varieties (V1–V8), and membership function analysis was used to determine a single Pb tolerance index. Of the eight watermelon varieties, V4 and V7 were ranked the most Pb tolerant; V1, V2, V5, and V6 were moderately Pb tolerant; and V3 and V8 were the most Pb-sensitive varieties. Compared with most Pb-sensitive varieties (V3 and V8), the most Pb-tolerant varieties (V4 and V7) maintained high antioxidant activity, and had lower malondialdehyde (MDA) and total soluble protein (TSP) contents. In addition, carotenoid and chlorophyll (both a and b) contents were stimulated and inhibited, respectively, in leaves of high-Pb translocation varieties (V4 and V8). Principal component analysis (PCA) revealed relative root length as an indicator of Pb tolerance because it correlated significantly with shoot growth. These results provide useful insight into the mechanism of Pb tolerance in cucurbit crops, as well as information regarding the breeding of watermelon with enhanced tolerance to this heavy metal (Pb).