The biomass increase of the plants without external N was most likely supported by the pool of internal N in the plant. At the time the external N supply was removed, the N content in the plants was above their CNC. The critical nitrogen content of a tissue is defined as the lowest amount of nitrogen in tissues that will allow for growth the growth of that tissue. Total plant biomass increased after the removal of the external N, which was evidence that photosynthesis must have continued. As more carbohydrates are produced and incorporated into the plant without an external supply of new nitrogen, the internal N/C ratio in the tissues will decrease. As described earlier, among the different tissues, leaves have the highest CNC, and will therefore reach this CNC earlier than tissues with lower CNC values. When the leaves reached their CNC, they could no longer incorporate more C into their own tissues, since this would reduce their N/C below the CNC and interfere with their function . At this point two scenarios are possible; one is that photosynthesis could shut down, and the other is that all the carbohydrates produced in the leaves could be transported to other tissues of the plant. Sweet potato leaves with N contents at CNC showed the same maximum photosynthesis rate as was observed when their N content was significantly below their CNC, and the leaf biomass was still increasing . For rhizomatous plants, the rhizomes have always been considered a sink for excess carbohydrates. The results of our P. australis study to-date suggests that the roots, as well as the rhizomes are tissues in which ‘excess’ carbohydrates can be incorporated. Experiments on storage root crops, strongly suggest that potassium, which causes phloem vessels to be wider, increases the storage root biomass . Wider phloem vessels would allow for more effective transport of photosynthates away from the leaves where they are produced,plant benches where they cannot be incorporated anymore. Thus avoiding a build-up of these photosynthesis products in their production vessel.

A study by Arp showed that photosynthetic acclimation originally attributed to the high CO2 treatment, occurs if the plants are completely root and rhizome bound. The time until this drop in photosynthesis rate occurred was directly related to the diameter of the pots in which the experimental plants were grown . This photosynthesis rate reduction was not observed in field grown plants without limitations on root and rhizome growth . If the plants physically do not have more room to grow roots and rhizomes, no new roots or rhizomes can be available to receive the translocated photosynthates, the photosynthesis products will indeed accumulate in the production vessel , and production will be lowered to a minimum maintenance level. With a N/C ratio of 0.00869 + 0.00037 rhizome CNC is 4.37x smaller than that of the leaves , the rhizomes can store 4.37 times as much C per molecule or gram of N in their tissues than the leaves can. At this time, the root N/C ratios have not been analyzed yet. Based on the growth of the roots of the no-nitrogen plants, especially when compared to that of the nitrogen supplied plants, we expect the N/C ratio of the roots to be low as well. The picture, based on our results to-date, of growth allocation in P. australis and the role of leaf N content suggest that rhizome and root growth continues after leaf N content has significantly decreased and the amount of senesced leaf tissue is almost as much as the amount of green leaves. Since the carbohydrates that ‘fueled’ this biomass increase were produced by photosynthesis and translocated from the leaves, the active ingredient of systemic herbicides applied at this time would still be transported to these roots and rhizomes, that are the target of the herbicide treatment.Under conditions of low iron availability, dicots and non-graminaceous monocot plants induce a three part Fe acquisition response to mobilize Fe within the rhizosphere and increase transport to roots. This process, commonly referred to as Strategy I, includes activation of proton pumps to acidify the rhizosphere, reduction of ferric iron to the ferrous form through a plasma membrane bound ferric reductase, and the uptake of ferrous iron by transporters localized to the plasma membrane of the root epidermis .

Physiological studies completed in pea suggest that iron reduction from the ferric to ferrous form is the rate-limiting physiological process in Fe acquisition . The pea mutants bronze and degenerative leaflet have been used by a number of studies to better understand the regulation of ferric reductase activity in plants . These pea mutants display a constitutive iron deficient root phenotype even under iron replete growth conditions leading to excessive iron accumulation in shoot tissue . Grafting experiments conducted with these mutant lines demonstrate constitutive expression of PsFRO1, the ferric reductase in roots of pea plants, suggesting that shoot based signals play a role in the regulation of Fe uptake in roots . Molecular and physiological studies in Arabidopsis thaliana have also demonstrated the importance of shoot-based signals in regulating ferric reductase activity , but the specific shoot signal and the mechanisms leading to reductase activity regulation have not yet been determined. We are interested in further dissecting the regulation of the ferric reductase in P. sativum and are examining the levels of reductase transcription and rates of enzyme activity across a range of pea accessions. We have selected twenty-nine different pea accessions from diverse geographic locales, and have included both commercial varieties and wild collected lines in order to incorporate a range of physiological and genetic backgrounds. To better understand the regulation of ferric reductase activity, these accessions have been evaluated for PsFRO1 transcription and ferric reductase activity when grown at low or high Fe hydroponic concentrations. The difference in transcript levels and reductase activity within each line following low or high Fe treatment is described, as is the correlation between relative differences in transcript abundance and activity. This study is part of a larger effort to understand how ferric reductase activity is regulated at the transcriptional and post-transcriptional levels.

To that end, an initial survey of ferric reductase transcription levels and ferric reductase activity was conducted across a range of geographically diverse pea plants grown under low and high Fe media to identify variation in iron acquisition responsiveness. The range of relative PsFRO1 transcription levels, and reductase activity is presented for the twenty-nine pea accessions maintained on low or high Fe treatment. PsFRO1 transcript levels were below detectable levels in accession 29 when grown at 15 µM Fe. Both relative transcript abundance and root-weight normalized reductase activity varied dramatically across the accessions. For low Fe grown accessions, the measured PsFRO1 transcript numbers varied by 9 PCR cycles , equivalent to a 512-fold range in transcript amounts.For high Fe grown accessions, the measured PsFRO1 transcript numbers varied by 7.5 PCR cycles , equivalent to a 180-fold range in transcript numbers. Reductase activity for the same plants varied 4.4-fold in activity level. From these results, it appears that reductase activity and PsFRO1 transcript levels vary significantly even in iron replete growth conditions across the pea accessions examined in this study . To determine whether transcript and activity differences seen between low and high Fe grown plants vary equally across the accessions, the relative change in transcript and activity values for each accession were determined. The correlation between changes in relative transcript levels and differential reductase activities between low- and high-Fe grown plants are illustrated in Figure 3. Our results suggest that across the twenty-nine pea accessions studied, there is no tendency for a change in transcript abundance to accurately predict the change in reductase activity. This study demonstrates that across a range of naturally occurring pea accessions, PsFRO1 transcription and reductase activity varies significantly. While greater differences are seen in transcription level across the accessions studied,rolling bench these differences do not strictly correlate with reductase activity. The range of reductase activity and ferric reductase transcription seen across these lines combined with the lack of correlation suggests a degree of variation in how pea accessions regulate ferric reductase activity. Further study of those pea accessions with altered regulation between transcription and activity may provide additional information of interest to identify the factors regulating ferric reductase in Strategy I plants. We are most interested in identifying those lines that show large changes in transcriptional levels but lack large differences in reductase activity and lines that show minimal changes in transcriptional levels between low and high Fe growth conditions but have very large changes in reductase activity. These two subsets of pea accessions will be further examined for differences in reductase transcripts, promoter regions and other factors that may explain the disconnect between PsFRO1 transcription and ferric reductase activity. More than 8.3 million utility patents have been issued in the United States since the establishment of the current patent numbering system in 1836, which makes the U.S. patent archive the world’s largest dossier of technological innovation and an unparalleled repository of built and unbuilt artifacts. The archive chronicles the ingenuity of millions of inventors and inventions, and illuminates the complex relations among humans, society, and the environments we make and inhabit. Each patent describes the unique function and configuration of a specific technology and protects the intellectual property and profits of the inventor. In aggregate, the patent archive portrays innovation and the evolution of technology, cultural ideas, and broader trends, and mirrors our ambitions toward the future.

This evolution is particularly salient for landscape architects as progress in sustainable, ecological, and landscape urbanisms raises the need for increasingly technological solutions to ecological imperatives and has brought about a sort of industrial revolution in disguise within the “green” industries.The tandem history of technology and landscape dates back to the earliest anthropogenic manipulations of environments and may be traced from the first woven fences that delineated cultivated ground from wilderness to the most advanced closed-circuit television surveillance and beyond. Technology and landscape imply and in many cases reflect each other! Thinkers such as Lewis Mumford, Leo Marx, David E. Nye, Karl Marx, and Robert L. Heilbroner have convincingly argued and illustrated the profound interrelations among technology, society, environment, politics, cities, landscapes, and everyday life. Given the complex and fascinating reciprocities between technology, landscape, and other constructed ecological and cultural networks, the profession of landscape architecture can claim its own legacy of innovation in the patent archive. But the challenge remains to define this legacy and to control and advance the technologies and productive systems that underpin our increasingly complex and technically sophisticated landscapes. Looking back into the patent archive reveals that landscape related technologies have a rich history of innovation, with cornerstones of contemporary sustainable site and building practices evolving well before notions of sustainability and wider environmental awareness. If landscape architects of the late 19th and early 20th centuries had become early adopters of newly patented landscape technologies, the profession might have been championing and implementing an engineered lightweight green roof substrate and water retention systems in 1886 , a precast permeable turf paver in 1940 , a decomposing geogrid for slope stabilization in 1933 , the vertical garden in 1938 , and anchoring trees to buildings in 1932 . The existence of these technologies gives depth and breadth to the history of landscape technology, providing valuable context to contemporary innovations. More than a century before the establishment of the Sustainable Sites Initiative and LEED, Charles Carroll Gilman of Eldora, Iowa, took it upon himself in 1886 to design and patent a porous terra-cotta substrate, water retention, and drainage system to support plant growth and storm water mitigation on a roof garden. Gilman’s invention solved storm water problems on his farm and in the local watershed; it also to this day provides landscape architects with important technological and cultural precedent for innovation in an era when schools of landscape and architecture were wholly concerned with the stylistic rigor of the Beaux-Arts, not the design of landscape systems and technology. How is it that the profession legally chartered with the production of landscapes is so distant from the technological innovation that underpins its materialization? Fascinating examples of landscape-related technologies exist in the patent archive dating back to its origins, with a noted uptick in the prewar and postwar eras, when patent submissions increased rapidly in all sectors of the mechanical and technical arts.