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This paper proposes a novel scheme of scalable coding for encrypted images. In the encryption phase, the original pixel values are masked by a modulo-256 addition with pseudorandom numbers that are derived from a secret key. After decomposing the encrypted data into a downsampled subimage and several data sets with a multiple-resolution construction, an encoder quantizes the subimage and the Hadamard coefficients of each data set to reduce the data amount. Then, the data of quantized subimage and coefficients are regarded as a set of bitstreams. At the receiver side, while a subimage is decrypted to provide the rough information of the original content, the quantized coefficients can be used to reconstruct the detailed content with an iteratively updating procedure. Because of the hierarchical coding mechanism, the principal original content with higher resolution can be reconstructed when more bitstreams are received.

Pot and field experiments were conducted to study the effects of mulching with straw of cadmium (Cd) tolerant plants (Ranunculus sieboldii, Mazus japonicus, Clinopodium confine and Plantago asiatica) on growth and Cd accumulation of Galinsoga parviflora in Cd-contaminated soil. In the pot experiment, mulching with M. japonicus straw increased the root biomass, stem biomass, leaf biomass, shoot biomass, plant height and activities of antioxidant enzymes (superoxide dismutase, peroxidase and catalase) of G. parviflora compared with the control, whereas mulching with straws of R. sieboldii, C. confine and P. asiatica decreased these parameters. Straws of the four Cd-tolerant plants increased the Cd content in roots of G. parviflora compared with the control. However, only straws of M. japonicus and P. asiatica increased the Cd content in shoots of G. parviflora, reduced the soil pH, and increased the soil exchangeable Cd concentration. Straw of M. japonicus increased the amount of Cd extraction in stems, leaves and shoots of G. parviflora by 21.11%, 29.43% and 24.22%, respectively, compared with the control, whereas straws of the other three Cd-tolerant plants decreased these parameters. In the field experiment, the M. japonicus straw also increased shoot biomass, Cd content in shoots, and amount of Cd extraction in shoots of G. parviflora compared with the control. Therefore, straw of M. japonicus can be used to improve the Cd extraction ability of G. parviflora from Cd-contaminated soil.

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