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Plant Senescence: The Role of Volatile Terpene Compounds (VTCs)

American Journal of Plant Sciences 2017年第12期8卷 3120-3139页

作者： Ernest Asante Korankye rajasekaran lada Sam Asiedu Claude Caldwell Christmas Tree Research Centre Department of Plant Food and Environmental Sciences Faculty of Agriculture Dalhousie University Halifax Canada

Senescence is a natural, energy-dependent, physiological, developmental and an ecological process that is controlled by the plant’s own genetic program, allowing maximum recovery of nutrients from older organs for the survival of the plant, as such;it is classified as essential component of the growth and development of plants. In some cases, under one or many environmental stresses, senescence is triggered in plants. Despite many studies in the area, less consideration has been given to plant secondary metabolites, especially the role of VTCs on plant senescence. This review seeks to capture the biosynthesis and signal transduction of VTCs, the physiology of VTCs in plant development and how that is linked to some phytohormones to induce senescence. Much progress has been made in the elucidation of metabolic pathways leading to the biosynthesis of VTCs. In addition to the classical cytosolic mevalonic acid (MVA) pathway from acetyl-CoA, the 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway, originating from glyceraldehyde-3-phosphate (GAP) and pyruvate, leads to the biosynthesis of isoprenoid precursors, isopentenyl diphosphate and dimethyl allyl diphosphate. VTCs synthesis and emission are believed to be tightly regulated by photosynthetic carbon supply into MEP pathway. Thus, under abiotic stresses such as drought, high salinity, high and low temperature, and low CO2 that directly affect stomatal conductance and ultimately biochemical limitation to photosynthesis, there has been observed induction of VTC synthesis and emissions, reflecting the elicitation of MEP pathway. This reveals the possibility of important function(s) of VTCs in plant defense against stress by mobilizing resources from components of plants and therefore, senescence. Our current understanding of the relationship between environmental responses and senescence mostly comes from the study of senescence response to phytohormones such as abscisic acid, jasmonic acid, ethylene and salicylic acid,

关键词： Senescence Abscission Volatile Terpene Compounds Phytohormone Plant Stress Plant Secondary Metabolites

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Advancement in Indoor Vertical Farming for Microgreen Production

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American Journal of Plant Sciences 2019年第8期10卷 1397-1408页

作者： Preethi Rajan rajasekaran R. lada Mason T. MacDonald Department of Plant Food and Environmental Sciences Faculty of Agriculture Dalhousie University Truro Truro N.S. Canada

With the growing global urban population and the emergence of megacities, there is a huge demand for arable land to meet the food demand and reduce malnutrition. Conventional agricultural practices lead to deforestation of the land for crop production and agricultural intensification to produce higher yield per unit area. These activities have been established to have negative impact on the environment thereby causing soil and water pollution. It is important to consider the use of vertical farming technology, which utilizes both horizontal and vertical space, and efficiently uses nutrients, water, and time (off season production with artificial lighting) more effectively to produce higher yield per unit volume of space than the conventional outdoor farming. Microgreens are taken into consideration to be grown under innovative vertical farming technology since they are rich in phytonutrients and they can be harvested in a short period of time. This paper reviews the current growing conditions of microgreens in vertical farming such as crop selection, media, light, nutrient solution, and containers while identifying knowledge gaps. Further, study in this area may lead to improved growing conditions to help solve the global issues and challenges surrounding food security, safety, and resource optimization.

关键词： Vertical Farming Microgreens Phytonutrients BioStrate Light Emitting Diodes Plant Nutrition

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Mechanical Shaking and Baling of Balsam Fir Trees Influence Postharvest Needle Senescence and Abscission

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American Journal of Plant Sciences 2018年第3期9卷 339-352页

作者： Ernest A. Korankye rajasekaran R. lada Samuel K. Asiedu Claude Caldwell Department of Plant Food and Environmental Sciences Faculty of Agriculture Dalhousie University Halifax NS Canada

This study investigated the influence of both shaking duration and number of trees per bale on postharvest needle characteristics such as percentage needle loss, needle retention duration and explored the physiological roles of endogenous ethylene and volatile terpene compounds (VTCs). To accomplish these objectives, 25 six-year-old trees were detached and exposed to a range of shaking durations (0 to 60 sec.), and 30 six-year-old detached trees were exposed to baling treatments from 0 to 5 trees. Response variables measured were percent needle loss, needle retention duration, average water use, ethylene and volatile terpene compound evolution. Trees shaken for 60 seconds lost 16% less needle compared to control, which was consistent with the decrease in percent needle loss with increasing shaking duration. Baled trees lost 13% more needles compared to control, but percent needle loss was observed to decrease with increasing number of trees in a bale. These trends corresponded with increasing ethylene and VTC evolutions, where the longer the shaking duration or larger number of trees in a bale, the higher the ethylene and VTC evolutions. One can therefore draw inference that mechanical perturbation as a result of shaking and baling induce biosynthesis and regulation of ethylene and VTC in balsam fir trees in an effort to regulate postharvest needle abscission.

关键词： Shaking Baling Ethylene Volatile Terpene Compounds Needle Loss Thigmomorphogenesis

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Qualitative Assessment of Postharvest Stomata and Chloroplast Degradation in Contrasting Abscission Resistant Balsam Fir (Abies balsamea (L.) Mill.)

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American Journal of Plant Sciences 2023年第9期14卷 1009-1028页

作者： Gaye MacDonald rajasekaran R. lada C. D. Caldwell Chibuike C. Udenigwe Mason T. Maconald Faculty of Agriculture Dalhousie University Bible Hill Canada School of Nutritional Sciences Faculty of Health Sciences University of Ottawa Ottawa Canada

Balsam fir is an important Christmas tree species, especially in eastern Canada. The natural Christmas tree industry faces a challenge in postharvest needle abscission. Though there have been many studies describing the physiological triggers and consequences in postharvest balsam fir, there have been no studies describing morphological or ultrastructural changes. Therefore, the objective of this study was to examine changes in stomata and chloroplast of postharvest needles. Branches were collected from low and high needle abscission resistance balsam fir genotypes, placed in water, and displayed in typical household conditions for 11 weeks. Needle abscission, chlorophyll fluorescence, and water uptake were monitored throughout. Needles stomata and chloroplasts were examined under a scanning and transmission electron microscope, respectively, each week. All branches had increased abscission, decreased chlorophyll fluorescence, and decreased water uptake over time. Needle surfaces accumulated fungal hyphae, especially in stomata. Chloroplasts demonstrated some dysfunction within two weeks, with notable decreases in chloroplast starch and increases in plastoglobulins. Within several weeks thylakoid membranes had been dismantled as chloroplasts transformed into gerontoplasts. All biophysical and structural changes were more pronounced in low needle abscission resistant genotypes. This research identifies a potential role for needle fungi in postharvest needle abscission and confirms the postharvest senescence of chloroplasts. Though it was previously speculated that chloroplasts must senesce postharvest, this study identifies how quickly this process occurs and that it occurs at different rates in contrasting genotypes.

关键词： Abies balsamea Balsam Fir Christmas Tree Fluorescence Needle Abscission Resistance Scanning Electron Transmission Electron

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Potential Roles of Fatty Acids and Lipids in Postharvest Needle Abscission Physiology

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American Journal of Plant Sciences 2019年第6期10卷 1069-1089页

作者： Gaye E. MacDonald rajasekaran R. lada Claude D. Caldwell Chibuike Udenigwe Mason T. MacDonald Department of Plant Food and Environmental Sciences Faculty of Agriculture Dalhousie University Halifax Canada School of Nutrition Sciences Faculty of Health Sciences University of Ottawa Ottawa Canada

Our understanding of postharvest needle abscission physiology in conifers has greatly improved in the last decade. Abscission is initially triggered by root detachment, which begins a cascade of changes such as decreased water uptake, water potential, and auxins and increased membrane injury, ethylene, abscisic acid, volatile terpenes, and catalytic enzymes. Needle abscission is also affected by environmental factors. For example, a period of cold acclimation generally delays postharvest abscission. The aforementioned pieces of evidence, along with previous studies, strongly points to a role for plant lipids and fatty acids. Studies from other species have pointed out key roles in abscission and stress responses for a variety of phospholipids and galactolipids, which has not been studied in balsam fir. It is imperative to have an understanding of the role of plant lipids and fatty acids to further our overall understanding of the physiological mechanisms of postharvest abscission and needle abscission resistance. This review is an overview of membrane lipids and fatty acids, changes that occur postharvest and the interaction that lipids may have in the phenomenon of postharvest abscission.

关键词： Phospholipids Galactolipids Fatty Acids Plant Growth Regulators Abscission

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Modern internet search analytics and thyroidectomy:What are patients asking?

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World Journal of Otorhinolaryngology-Head and Neck Surgery 2024年第1期10卷 49-58页

作者： Neeraj Suresh Christian Fritz Emma De Ravin Karthik rajasekaran Department of Otorhinolaryngology–Head&Neck Surgery University of PennsylvaniaPhiladelphiaPennsylvaniaUSA Perelman School of Medicine at the University of Pennsylvania PhiladelphiaPennsylvaniaUSA Leonard Davis Institute of Health Economics University of PennsylvaniaPhiladelphiaPennsylvaniaUSA

Objectives:Thyroidectomy is among the most commonly performed head and neck surgeries,however,limited existing information is available on topics of interest and concern to *** Design:***:***:A search engine optimization tool was utilized to extract metadata on Google‐suggested questions that“People Also Ask”(PAA)pertaining to“thyroidectomy”and“thyroid surgery.”These questions were categorized by Rothwell criteria and topics of *** Journal of the American Medical Association(JAMA)benchmark criteria enabled quality ***:A total of 250 PAA questions were ***‐oriented PAA questions describing what to expect during and after the surgery on topics such as postoperative management,risks or complications of surgery,and technical details were significantly less popular among the“thyroid surgery”group(P<0.001,P=0.005,and P<0.001,respectively).PAA questions about scarring and hypocalcemia were nearly threefold more popular than those related to pain(335 and 319 vs.113 combined search engine response page count,respectively).The overall JAMA quality score remained low(2.50±1.07),despite an increasing number of patients searching for“thyroidectomy”(r(77)=0.30,P=0.007).Conclusions:Patients searching for the nonspecific term“thyroid surgery”received a curated collection of PAA questions that were significantly less likely to educate them on what to expect during and after surgery,as compared to patients with higher health literacy who search with the term“thyroidectomy.”This suggests that the content of PAA questions differs based on the presumed health literacy of the internet user.

关键词： information quality online health education search analytics thyroid surgery thyroidectomy

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Isolated traumatic orbital floor fracture: An analysis of the National Trauma Data Bank

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世界耳鼻咽喉头颈外科杂志英文版 2024年第3期10卷 187-192页

作者： De Ravin Emma Xu Katherine Fritz Christian S. Parhar Harman rajasekaran Karthik Department of Otorhinolaryngology Head and Neck Surgery University of Pennsylvania Philadelphia Pennsylvania USA Perelman School of Medicine at the University of Pennsylvania Philadelphia Pennsylvania USA Leonard Davis Institute of Health Economics University of Pennsylvania Philadelphia Pennsylvania USA

Objectives: To date, no study provides a comprehensive analysis of traumatic orbital floor fractures across the United States. We aimed to characterize patient demographics, injury-related variables, and operative management in this ***: The National Trauma Data Bank was queried for open or closed orbital floor fractures from 2008 to 2016. Clinical data were ***: Overall, 148,592 orbital floor fractures were identified, with 142,577 (95.9%) closed- and 6158 (4.1%) open-type fractures. A total of 106,243 (71.5%) patients were male and the median patient age was 41 years. The majority of patients (79.2%) had abbreviated injury scale scores of ≤2, indicating minor/moderate injury. Fracture mechanism of injury (MOI) differed by gender, with the most frequent being unarmed fights in men (34.3%) and falls in women (14.0%). There were 29,600 patients (19.9%) with isolated orbital floor (I-OF) fractures. The MOI most strongly associated with operative intervention of with I-OF fractures were penetrating injuries caused by a firearm (odds ratio [OR]: 2.91; 95%confidence interval [CI]: 1.62–5.20) and cuttings/piercings (OR: 2.17; 95%CI: 1.29–3.65).Conclusion: This large epidemiological study reveals that orbital floor fractures tend to present with minor or moderate injuries and are more likely to require operative intervention in setting of firearm or cut/pierce injuries.

关键词： epidemiology National Trauma Data Bank orbital fracture risk factors trauma

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Emerging technological developments to address pest resistance in Bt cotton

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Journal of Cotton Research 2024年第03期 318-333页

作者： NAGARAJ Selvarani rajasekaran Ravikesavan PALANIAPPAN Jayamani RANGASAMY Selvakumar NARAYANASAMY Chitra NARAYANAN Manikanda Booapathi Department of Genetics and Plant Breeding Centre for Plant Breeding and Genetics(CPBG) Tamil Nadu Agricultural University(TNAU) Centre for Plant Breeding and Genetics TNAU Department of Pulses CPBG TNAU Research and Development Centre Rasi Seeds(P)Ltd. Department of Cotton TNAU Department of Plant Biotechnology Centre for Plant Molecular Biology and Biotechnology(CPMB&B) TNAU

Cotton plays a crucial role in shaping Indian economy and rural livelihoods. The cotton crop is prone to numerous insect pests, necessitating insecticidal application, which increases production costs. The advent of the expression of Bacillus thuringiensis(Bt) insecticidal protein in cotton has significantly reduced the burden of pest without compromising environmental or human health. After the introduction of transgenic cotton, the cultivated area expanded to 22 million hectares, with a 64% increase in adoption by farmers worldwide. Currently, Bt cotton accounts for 93% of the cultivated cotton area in India. However, extensive use of Bt cotton has accelerated resistance development in pests like the pink bollworm. Furthermore, the overreliance on Bt cotton has reduced the use of broad-spectrum pesticides, favouring the emergence of secondary pests with significant challenges. This emphasizes the urgent necessity for developing novel pest management strategies. The high-dose and refuge strategy was initially effective for managing pest resistance in Bt cotton, but its implementation in India faced challenges due to misunderstandings about the use of non-Bt refuge crops. Although gene pyramiding was introduced as a solution, combining mono toxin also led to instances of cross-resistance. Therefore, there is a need for further exploration of biotechnological approaches to manage insect resistance in Bt cotton. Advanced biotechnological strategies, such as sterile insect release, RNA interference(RNAi)-mediated gene silencing, stacking Bt with RNAi, and genome editing using clustered regularly interspaced short palindromic repeats/CRISPR-associated protein(CRISPR-Cas), offer promising tools for identifying and managing resistance genes in insects. Additionally, CRISPR-mediated gene drives and the development of novel biopesticides present potential avenues for effective pest management in cotton cultivation. These innovative approaches could significantly enhance the

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Advancement in Indoor Vertical Farming for Microgreen Production

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American Journal of Plant Sciences（美国植物学期刊） 2019年第8期

作者： Preethi Rajan rajasekaran R. lada Mason T. MacDonald

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Nutrition and Related Factors Affecting Maple Tree Health and Sap Yield

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American Journal of Plant Sciences（美国植物学期刊） 2023年第2期

作者： Rachel R.West rajasekaran R.lada Mason T.MacDonald

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