Reducing the “need” to fish by increasing available aquaculture derived food and materials does not necessarily equal reduced fishing pressure. Political/economic input will likely be needed to achieve the conservation goal of reduced fishing pressure as an outcome of implementing a FFP project.I would argue that new research paths in algae culture for bio-fuel production need to be followed in order to achieve results for application in the near-term. Maximum solar conversion efficiency are likely not necessary for commercial success with algae culture for bio-fuels— particularly in the case of food and fuel poly culture systems. A focus on simple easily applied culture techniques may yield a similar cost/benefit ratio per unit invested compared to employing the latest intensive technology to achieve maximum yield. Research and development efforts should be refocused toward small to medium scale ideas and projects with an emphasis on applied, relatively low-tech systems. The overwhelming majority of past and current work pertaining to algae culture for bio-fuel production is concentrated on microalgae. Microalgae holds great promises and this work should continue, but active work with macroalgae for bio-fuel production should be initiated and receive at minimum a similar level of effort. Screening of potential macroalgae candidate species for bio-fuel production, and developing technology transfer from current commercial algae farming operations for use in FFP systems are strongly recommended starting points. The concept of food and fuel poly culture is in its infancy, but with moderate investments in research to further develop the system’s components,greenhouse vertical farming the concept can play a role in providing food and energy to the world’s population while at the same time helping to conserve valuable natural resources— particularly those in at risk aquatic ecosystems.The rotation of the Earth acts to confer regular environmental changes in light availability and temperature and plants alter their physiology, biochemistry, and metabolism in response to these abiotic cues over the course of a day .
In addition, the inherent regularity of the transition between day and night also allows alterations in temperature and light to be predictive of subsequent abiotic stresses. For example, dusk is typically accompanied by a decrease in temperature and possible frost. It is therefore unsurprising that plants have developed an internal timing mechanism that allows prescient alterations in gene expression and biochemistry. Indeed, the circadian clock causes the regular oscillation of between 30% and 40% of genes in the model plant Arabidopsis thaliana , even when grown under constant light and temperature . These broad changes in gene expression precipitate a range of physiological responses including the regulation of hypocotyl growth , alterations to plant hormone production and sensitivity and time of flowering . In concert, such changes promote the fitness of plants grown in synchrony between endogenous and environmental cues . Circadian clocks are conceptually thought to be comprised of three parts: a central oscillator typically consisting of a negative feedback loop, input pathways to allow entrainment to local environmental conditions, and output pathways which act to modulate responses dependent on these endogenous cues. Although at its most basic level a circadian clock can consist of a single negative feedback loop with input and output pathways , evolution has typically led to the development of multiple interconnected molecular oscillators with varied levels of redundancy . The inclusion of partially redundant interlocking components likely allows greater flexibility in the modulation of clock inputs during evolution while also allowing greater accuracy of the timing mechanism itself . In addition to these core concepts, circadian clocks are recognised as having additional properties including temperature compensation and “gating”. Temperature compensation allows a circadian clock to oscillate at approximately the same frequency over a broad range of physiological temperatures while gating refers to the regulated sensitivity of the central oscillator to input stimuli. This latter mechanism enables the circadian clock to persist in plants grown in constant experimental conditions by reducing the responsiveness of core components to light during the subjective night .The other dominant zeitgeber of the Arabidopsis circadian clock is temperature, with steps as small as 4°C being capable of entraining the clock mechanism . The majority of large-scale mutant screens to identify Arabidopsis clock genes have used light as an entrainment signal and it is therefore unsurprising that comparatively little is known about temperature-sensitive entrainment of the clock.
It does appear, however, that the circadian regulation of individual genes may differ based upon the entrainment conditions used; CAB2 and TOC1 expression are similarly modulated by light and temperature whereas the phase of CAT3 expression is more sensitive to changes in temperature than light . Temperature inputs into the clock are at least in part incorporated via loops containing PRR7 and PRR9 as a prr7 prr9 double mutant is unresponsive to circadian phase changes induced by temperature and is arrhythmic if entrained to temperature steps . In contrast, it appears that TOC1 has a minor role in this mechanism as a toc1 mutant retains a wild-type entrainment response to temperature steps . Further characterization of this sensitivity is dependent upon identification of temperature sensors in Arabidopsis.Animal circadian clocks have long been recognized to contain a master clock which synchronizes multiple “slave” clocks in other tissues . This hierarchical arrangement of the clock permits individual tissues to utilize subsets of circadian genes . In comparison, plants are thought to measure time using cell-autonomous circadian oscillators , although it has remained unclear until recently whether each of these independent plant clocks sharecommon core components across different cell types. It now appears that certain loops of the plant clock act predominantly in certain tissues. PRR3 has been shown to be predominantly expressed in Arabidopsis vasculature while recent microarray analysis has indicated that only a subset of genes known to have a circadian expression pattern in aerial tissues oscillate in hydroponically grown roots . Such data suggest that circadian rhythmicity in roots is controlled by a simplified mechanism and is dramatic evidence that plant circadian rhythms need not be controlled by a uniform set of components. In support of this concept, experiments using RNAi to reduce PRR3 mRNA levels induce a greatly pronounced shortening of the circadian clock when measured using vasculature-specific luciferase reporter constructs in comparison to those with a broader range of expression . The use of modified clock circuitry in different plant tissues likely allows altered sensitivity to environmental stimuli and stresses and it will be interesting in the future to determine the functional role of tissue-specific circadian oscillations.Our understanding of the Arabidopsis circadian clock at a transcriptional level has progressed rapidly, aided by the high-throughput capabilities of luciferase reporter mutant screens and micro-array assays. While it is clear that a large percentage of the transcriptome is regulated by the circadian clock , our understanding of the molecular processes underlying these large-scale changes in transcription remains limited. Recent work has identified a correlation between histone acetylation and transcriptional activity at the TOC1 locus and similarly, a degree of histone methylation is associated with changes in transcriptional activity at CCA1 and LHY loci . Both of these observations suggest that epigenetic marks may regulate circadian gene expression and identification of proteins responsible for these epigenetic marks will allow a more thorough understanding of transcriptional regulation by the clock. While transcriptional regulation is clearly important for Arabidopsis clock function,vertical agriculture it is also increasingly clear that the rhythms generated by the transcriptional clock are modulated by a range of post translational modifications. TOC1 and PRR proteins are differentially phosphorylated and degraded over the course of a day while ZTL protein accumulates with a circadian rhythm despite being transcribed at a regular rate .
It is equally apparent that endogenous rhythms are regulated by changes in cytosolic composition, such as the concentration of free Ca2+ . Considering these examples, it is unlikely that we have either identified all components of the Arabidopsis clock or that we yet fully understand the subtleties of action and regulation of characterized transcripts and proteins. Ultimately, it will be important to transfer our understanding of the clock to real-world applications. Given the suggested role of the circadian clock in the regulation of plant responses to abiotic stresses , it is possible that altering expression of certain clock components may confer enhanced stress tolerance. Indeed, Arabidopsis prr5 prr7 prr9 triple mutants have recently been reported to have an enhanced cold, drought, and salt tolerance, caused by increased expression of stress-responsive genes . Such data are in agreement with work demonstrating that plants are differentially responsive to temperature over the course of a day and that this gating is controlled by the circadian clock . Further work to understand the process by which stress response pathways and the circadian clock interact will likely be a fruitful course of investigation.The biological oxidation of ammonia is carried out by two groups of chemotrophic bacteria , a process termed ‘nitrification’, results in transformation of NH4 + to NO3 – , making soil nitrogen susceptible to losses through multiple pathways – leaching and gaseous losses . Due to these nitrogen losses, a major portion of the soil nitrogen and applied fertilizer nitrogen is lost, in low nitrogen-use efficiency of agricultural systems . Also, nitrogen pollution is the single most environmental concern from agricultural systems, contaminating ground and surface water . Denitrification of nitrate-N is the major source of nitrous oxide emissions from agricultural systems and contributes significantly to global warming . Blocking the function of nitrifying bacteria or slowing the nitrifiers’ function can significantly reduce nitrogen losses associated with nitrification and extend the persistence of nitrogen as ammonium in the soil for uptake by plants, lead to improved nitrogen recovery and – use efficiency in agricultural systems . Recently, it was shown that some plant species have the ability to release nitrification inhibitors from roots that suppress nitrifiers’ function, a phenomenon termed ‘biological nitrification inhibition’ . Using a luminescent recombinant Nitrosomonas, an assay has been developed to detect and quantify this inhibitory effect in plant soil systems . With this newly developed methodology, it was shown that several tropical grasses and certain field crops including sorghum possessed the ability to release nitrification inhibitors from roots, termed BNI-capacity . We showed that sorghum roots release methyl 3-propionate , one of the active constituents with BNI activity of root exudates from sorghum . Here we present our findings on further characterization of BNI function in sorghum and reveal the identity of the two nitrification inhibitors released from its roots. In addition, we present evidence to show wide genetic variability in the release capacity of one of the major nitrification inhibitors from sorghum roots and also report preliminary field-based results for the existence of BNI-capacity in wild sorghum. Root architecture influences nutrient and water uptake, anchorage, and mechanical support, interactions with microbes, and responses to various abiotic stress factors . Since water and mineral supply are often limited in the soil, a plant with a more extensive root system exhibits higher performance with regard to the tolerance of drought and poor nutrient conditions . Several factors, including root angle, root growth rate, and root types, influence root architecture . Root growth requires the successive formation of new cells from stem cells in the root apical meristem , and the progeny of such stem cells divide rapidly and enter the elongation/differentiation zone . To maintain root meristem activity, the rates of cell division and differentiation have to be coordinated . In addition, the interaction between cytokinin and auxin determines the size of the RAM through the regulation of the genes involved in auxin signaling and/or transport to ensure an appropriate auxin gradient . The rice root system consists of one seminal root, numerous adventitious roots, and lateral roots that emerge from the other two types . Lateral roots are the major components involved in the absorption of nutrients and in interactions with the surrounding soil environment . Lateral root formation represents a complex developmental process modulated by several hormones, including auxin and ethylene.Well defined and closely coordinated cell division activities give rise to lateral root primordia.While lateral roots originate from pericycle cells adjacent to xylem poles in Arabidopsis,pericycle and endodermal cells located near phloem poles are the origins of lateral roots in rice and maize . Their development is initiated by the asymmetric division of the pericycle cells, and subsequent divisions result in the formation of dome-shaped, multilayered, lateral root primordia .