compare the way data is store and retrieved in a floppy disk and a CD ROM
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Answer:Plants live in a world populated by numerous and varied herbivores and microbial pathogens that include insects, nematodes fungi, bacteria, and oomycetes. However, plants have evolved mechanisms to detect such attacks and counteract them with efficient immune responses. Much of our knowledge about pathogen recognition of plants originates from studies of plant–microbe or plant–insect/herbivore interactions, in which plant immunoreceptors detect specific microbe-associated molecular patterns (MAMPs) that are often highly conserved microbial structures, such as bacterial flagellin or fungal chitin. Activation of these immunoreceptors, also termed pattern recognition receptors (PRR), triggers a set of typical defense responses that include rapid production of reactive oxygen species (ROS-burst), elevation of the stress-related phytohormone ethylene, increased levels of secondary metabolites (callose, phytoalexins, lignins, etc.) and the induction of characteristic marker genes (Boller and Felix, 2009; Böhm et al., 2014). Additionally, plant defense responses include signaling via networks controlled by the phytohormones salicylic acid (SA) and jasmonic acid (JA; Dong, 1998; Wasternack et al., 2006). In particular, SA is required for the initiation of a hypersensitive response (HR) and to trigger systemic acquired resistance (SAR; Durrant and Dong, 2004). Taken together, plants present a complex network of defense reactions to fend off pathogens or at least to restrict the pathogen growth and spread.
Apart from microbial pathogens and herbivorous arthropods, plants are also parasitized by other plants. Parasitic plants feed on their hosts (from the Greek para = beside; sitos = food) and keep them alive until they have completed their life cycle. Most often the parasite’s life cycle is completed earlier than the one of the host plant which leads to a premature death of the parasitized plants and thus can cause crop damage. Parasitic plants are categorized as either obligate or facultative parasites, depending on whether they rely totally on their hosts to complete their life cycle (obligate) or are able to survive on their own in the absence of their host plants (facultative). Additionally, parasitic plants can be divided into hemiparasites that rely only partially on a host plant and are still able to make photosynthesis and holoparasites that are completely dependent on photoassimilates, solutes, and metabolites from their host plants. According to their preferred target host organ, parasitic plants are defined as either root or shoot parasites.
Here, we describe the parasitic plant Cuscuta spp.—also known as dodder—which can be defined as an obligate stem holoparasite. Besides describing its life style and mechanisms for infecting susceptible host plants, we will focus on Cuscuta spp. as pathogens. Using mainly tomato vs. Cuscuta reflexa as an example, resistance mechanisms of plants against plant parasites will be illustrated and discussed, highlighting future prospects of controlling Cuscuta infestations during crop cultivation.
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