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  • Author or Editor: Shirong Guo x
  • HortScience x
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The chloroplast structural alteration and the photosynthetic apparatus activity of cherry tomato seedlings were investigated under dysprosium lamp [white light control (C)] and six light-emitting diode (LED) light treatments designated as red (R), blue (B), orange (O), green (G), red and blue (RB), and red, blue, and green (RBG) with the same photosynthetic photon flux density (PPFD) (≈320 μmol·m−2·s−1) for 30 days. Compared with C treatment, net photosynthesis of cherry tomato leaves was increased significantly under the light treatments of B, RB, and RBG and reduced under R, O, and G. Chloroplasts of the leaves under the RB treatment were rich in grana and starch granules. Moreover, chloroplasts in leaves under RB seemed to be a distinct boundary between granathylakoid and stromathylakoid. Granathylakoid under treatment B developed normally, but the chloroplasts had few starch granules. Chloroplasts under RBG were similar to those under C. Chloroplasts under R and G were relatively rich in starch granules. However, the distinction between granathylakoid and stromathylakoid under R and G was obscure. Chloroplasts under O were dysplastic. Palisade tissue cells in leaves under RB were especially well-developed and spongy tissue cells under the same treatment were localized in an orderly fashion. However, palisade and spongy tissue cells in leaves under R, O, and G were dysplastic. Stomatal numbers per mm2 were significantly increased under B, RB, and RBG. The current results suggested blue light seemed to be an essential factor for the growth of cherry tomato plants.

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Soil sickness from the continuous cropping of cucumbers has become a major limiting factor for protected cucumber cultivation. The use of reasonable cropping systems and the employment of allelopathy between different crops are considered to be the major safe and effective measures for alleviating soil sickness. The objective of this study assessed the effects of garlic (Allium sativum L. cv. Yusuan No. 1)/cucumber (Cucumis sativus L. cv. Jinchun No. 4) relay intercropping on soil enzyme activities and the microbial environment in a continuous cropping regime. Cucumbers and garlic were selected and planted in plastic barrels. The following four treatments were included in the experiment: continuous cropping without crops (Cont), monoculture cucumbers (C), monoculture garlic (G), and the relay intercropping of garlic with cucumbers (CG). The results showed that relay intercropping with garlic promoted cucumber plant growth and attenuated damage caused by soil sickness. In comparison with the Cont treatment, the C treatment decreased soil urease, catalase, invertase, and phosphatase activities; by contrast, the CG treatment enhanced all soil enzyme activities. The C treatment resulted in lower numbers of soil bacteria and actinomycetes and a lower bacteria/fungi ratio, but there were a higher number of soil fungi than there were in the Cont treatment. However, the CG treatment increased the numbers of soil bacteria and actinomycetes as well as the bacteria/fungi ratio, and it decreased the number of soil fungi. In comparison with the Cont treatment, the C treatment reduced the microbial biomass carbon (MBC) and soil basal respiration (BSR) without affecting the metabolic quotient (qCO2), whereas the CG treatment increased all three variables. A polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE) analysis revealed decreased bacterial community diversity and increased fungal community diversity in soil with the C treatment; the opposite trend was observed in the CG treatment. The results indicated that the relay intercropping of garlic with cucumbers improved soil enzyme activities and promoted the conversion of continuous cropping soil from a “fungal” type to a “bacterial” type. Additionally, relay intercropping altered the soil bacterial community structure, increased the bacterial diversity indices, and enriched the dominant bacterial populations in the soil. These mechanisms improved the soil microbial environment and effectively alleviated damage caused by soil sickness, thus promoting cucumber plant growth.

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