In addition, investigation of monovalent cation selectivity of OsHKT1;4 expressed in oocytes bathed in solutions containing solo cation-chloride salts further revealed that this transporter is highly selective for Na+ amongst Li+ , K+ , Rb+ , Cs+ , Na+ , and NH4 + . These results indicate that OsHKT1;4 is a Na+ transporter. HKT proteins have been suggested to contain four selectivity-filter-pore domains that are distantly related to a bacterial K+ channel. HKT1 transporters have been found to be highly selective for Na+ , and in general a serine residue at the key amino acid position for K+ selectivity in the first p-loop domain is conserved instead of a glycine residue, which corresponds to the first glycine in the GYG motif of the shaker-type K+ channel. Corresponding amino acid positions in the three other p-loop domains of OsHKT1;4 were reported to be glycine residues, resulting in a SGGG type for the p-loop domains of OsHKT1;4 as typical HKT1 transporters. The property of Na+ selective transport by OsHKT1;4 was consistent with the prediction of Na+ selectivity of HKT transporters based on the p-loop hypothesis. QTL analyses for salt tolerance of durum wheat plants have led to the identification of the salt tolerance determining Nax1 locus, which was deduced to be the TmHKT1;4-A2 gene. The Nax1 locus mediated xylem Na+ unloading in roots and leaf sheaths of durum wheat plants has been suggested to avoid Na+ over-accumulation in leaf blades during salinity stress. Relatively steady expression in leaf sheaths throughout growth stages is a distinctive feature of the OsHKT1;4 gene in Nipponbare plants . In 3-weekold Nipponbare plants, grown in hydroponic culture, the expression of OsHKT1;4 was also observed in roots . However, the level of OsHKT1;4 expression mostly showed significant decreases in tissues/organs of salt-stressed Nipponbare plants at the vegetative growth stage under salinity stress . OsHKT1;4 RNAi plants in the vegetative growth stage did not show any noticeable difference either in visual phenotype or in Na+ content after the imposition of 50 mM NaCl stress compared with Nipponbare wild-type plants . These results suggested a possibility that OsHKT1;4- mediated Na+ transport does not provide a profound contribution to vital Na+ homeostasis during the vegetative growth phase of the japonica rice cultivar during salinity stress. Another characteristic feature of OsHKT1;4 gene expression was its high expression in the stem,hydroponic channel including the peduncle and the internode II, of rice plants at the reproductive growth stage .

The observed expression profile of OsHKT1;4 was consistent with that found in the RiceXPro database, in which OsHKT1;4 is highly up-regulated in the stem of rice plants in heading and ripening stages. Longterm salinity stress treatment with gradual increases in NaCl concentration in soil-grown Nipponbare plants from heading to ripening stages led to significant increases in OsHKT1;4 expression in the peduncle, with relatively steady expression levels in the flag leaf blade and internode II independent of salt treatments . Significant up-regulation of OsHKT1;4 expression was also observed in node I, although the basal expression level in this tissue was far less than that in the peduncle . Similar long-term salinity stress treatments of soil-grown OsHKT1;4 RNAi and wild-type plants resulted in significantly higher Na+ contents in aerial tissues of RNAi plants, with the highest impact on the Na+ content of flag leaf blades compared with wild-type plants . Together with Na+ selective transport mediated by plasma membrane-targeted OsHKT1;4 , these results suggested that OsHKT1;4 contributes to the prevention of Na+ over-accumulation in aerial parts, in particular leaf blades of Nipponbare plants that are in the reproductive growth stage, during salinity stress. HKT1;4 transporters in wheat have been suggested to function in xylem Na+ unloading in roots and leaf sheaths upon salinity stress to reduce Na+ transfer into leaf blades. On the other hand, HKT1-mediated Na+ recirculation via the downward stream of the phloem has been argued as a potential working model for HKT1 transporters. OsHKT1;4 RNAi plants in the reproductive growth stage accumulated more Na+ not only in leaves but also in tissues of the stem investigated under salinity stress . The reason for the phenotype is not clear yet. In a previous study, analyses on athkt1;1 mutants of Arabidopsis indicated that the dysfunction of AtHKT1;1- mediated Na+ unloading from xylem caused the impairment of Na+ recirculation via phloem as well, which could together be attributed to Na+ over-accumulation in shoots of athkt1;1 mutants upon salinity stress. 22Na+ -imaging analysis indicated a higher amount of the Na+ transfer in peduncles of OsHKT1;4 RNAi plants than WT plants with an exception of an independent OsHKT1;4 RNAi-II plant , suggesting that OsHKT1;4 mediates Na+ unloading from xylem and reduced activity of OsHKT1;4 leads to an increase in Na+ accumulation in this tissue.

Together, Na+ over accumulation in aerial parts of OsHKT1;4 RNAi plants upon salinity might be due to the insufficient activity of OsHKT1;4 in Na+ unloading from xylem, which in turn could also bring about inhibition of Na+ recirculation. To elucidate the precise function of OsHKT1;4 in Na+ exclusion in rice, a detailed investigation into whether OsHKT1;4 predominantly mediates xylem Na+ unloading or phloem-involved Na+ recirculation or both will be an essential question to be addressed in future research. In this respect, it will be also interesting to study the in planta localization of OsHKT1;4 in order to investigate possible regulatory mechanisms that can control its PM localization, and hence Na+ transport and salt tolerance. Indeed, our subcellular localization analyses leave room for some speculation. Using rice protoplasts, we could clearly observe the PM localization of OsHKT1;4 , but also the presence of the protein in unidentified vesicles that were neither ER nor GA structures . This vesicle could represent a means to control the abundance of OsHKT1;4 in the PM. Recently it has been demonstrated that another member of the HKT family, OsHKT1;3, is targeted to the GA and undergoes strict control of its trafficking. Note that the subcellular localization of OsHKT1;4 was investigated using rice protoplasts over-expressing the chimeric EGFPOsHKT1;4 protein. The hypothesis that endocytotic mechanisms regulate the amount of OsHKT1;4 in the PM requires further investigation using rice plants. In addition to aerial tissues, increases in the Na+ content of ripening grains from OsHKT1;4 RNAi plants were found during salinity stress conditions compared with wild-type plants . The expression of OsHKT1;4 was up-regulated by salt stress in the peduncle and node I . In Node I, it was also found by LMD-combined qPCR analysis that the OsHKT1;4 gene was predominantly expressed in the DVB, which is connected to the ear of rice. Taken together, these results suggested a potential contribution of OsHKT1;4 in protecting reproductive organs and seeds from Na+ toxicity in rice plants in addition to the leaf blades upon salinity stress .

Each of us was born somewhere and has an ancestral lineage that connects us to that place, or to distant locales, known and imagined. We crave the experience of travel, and we insert visual notations of our journeys into our everyday lives with bits of natural detritus, mementos and photographs. Each object, relic or image, imbued with the distilled essence of its place of origin, is reframed by and reframes its new surroundings. Although we may appreciate a saved pebble for its essential qualities as a stone, it also holds its own history and has the potential to evoke deeply personal, experiential memories. Artist’s expressions of their relationships to place have long served as important indicators of the shifting formal innovations and philosophical tenor of their times. The Impressionists’ aspiration to capture the transient light and color in a landscape with fleeting brushwork and a subjective palette was central to their desire to represent modernity in the nineteenth century. For the emerging middle class at that time, the rapidly changing urban world had stimulated a desire for scenes of rural landscape and life. Such scenes reassured them there were still places where timeless values could be found. The duality of this situation opened the possibility for a technically and conceptually innovative avantgarde,hydroponic dutch buckets and as artists expanded the paradigm for modern subject matter throughout the twentieth century, some began to merge formal radicalism with social commentary about the changing landscape. The importance of the relationship between nature and culture intensified during the late 1960s, as artists began to eradicate the boundaries between form, process and meaning, shifting their relationship to the location and presentation of their work. Two major trajectories eventually emerged. Land- or Earthworks artists asserted their relationship to nature with performance-based works or large scale sculpture in remote locations. Minimalists responded to this institutional shift and telluric urge by transporting earth and other natural materials into the white cube of the gallery. As artists embraced this new aesthetic, their work also evolved to incorporate formal eclecticism, performative practice, and the primacy of conceptual expression. The legacy of this period has been a generation of artists who have adapted these methodologies to establish ideational, emotional and aesthetic bridges between the personal and public. Their confrontation of the not-sodelicate balance between nature and culture has compelled many of them to create works that commingle elements of the natural world with personal narrative to showcase issues that might otherwise be overlooked.Parker’s deep artistic and philosophical connections to the materials of nature is shared by a growing number of contemporary artists involved with liberating natural materials from their utilitarian identities and presenting them for aesthetic, symbolic and scientific contemplation.

Among them is Wolfgang Laib, whose art is largely concerned with gathering pollen, which he exhibits as material and art object. Laib’s sensibility is similar to Parker’s in that he allows the pollen to retain its own character and meaning. His process of gathering it also mimics the bee’s rites of collection. Laib’s holistic attitude toward his primary material, the creatures that cultivate it, and his reference to nature as “his monastery” have poetic resonance with Parker’s empathy toward the land, its output, and place.2 But Parker also says her “personal hunger to have connection with the land is a form of spirituality.” She speaks of her paintings, which reduce the landscape to geometrically patterned fields of color, as “more about the spirit of the land than a direct replication of it.” The material and pieces that speak most deeply of Parker’s connection to the land are those that are comprised of earth or that tell stories about it. For several years she has been collecting soil samples from various farms, which she uses as subject and medium. “The soil is really the palette, and you can’t make anything if the soil isn’t of quality.” During her exhibition’s opening, Parker glamorized the experience of soil quality by setting small portions of damp soil in wine glasses for people to test its aroma. For “Palette,” she displayed small samples in see-through containers in a box, creating an earth palette of assorted colors and textures. One particularly meaningful soil sample was gathered from her partner’s family farm in France, which “had not been disked or turned over for a hundred years. There was something poignant to me about these people living on their land, who don’t turn some of it over; who don’t impact it in any major way. I loved that soil and the idea that there’s a place where people don’t mess with the earth.” Parker’s personal identification with the soil is distilled in “Clod,” a chunk of earth which floats serenely atop a transparent Plexiglass pedestal, as her emblematic alter ego.Parker’s interest in the stories embodied in the earth was intensified one evening while she was sharing a meal with Willey and his wife denesse. As she describes it, during a conversation Tom leaned across the table with his hand open and said, “There are more microorganisms, more living things in a palm full of dirt, than there are people on the planet.” Parker was astounded by the microcosmic/macrocosmic implications of this statement: that a two-inch circle of dirt on one’s palm could contain billions of microorganisms. It motivated her to contact a soil biologist to obtain their names, which she intended to write on the gallery walls as part of her installation. However, when she received the extensive list, she decided to write their names, layer upon layer, in ink on earth-stained canvas, to emulate the vertical strata of the microorganisms in nature.