Relationship Between Hyperspectral Parameters and Physiological and Biochemical Indexes of Flue-Cured Tobacco Leaves

The experiment was set up for examining the physiological and biological indexes quickly and exactly, for obtaining information of tobacco-field fertilizing and tobacco growing. The ASD Field spec FR 2500 was used to measure spectra reflectance of flue-cured tobacco and the relationship between hyperspectral parameters and biochemical contents （total nitrogen, chlorophyll, carotenoid）, and physiological indexes （fresh weight, dry weight, moisture content） of flue-cured tobacco leaves was studied by correlation and stepwise regression statistic methods at different nitrogen and potassium levels. The results indicated that the spectra curves of different treatments had obvious rules and great diversities. There were high correlations between different types of spectra parameters and ten physiological and biochemical indexes of flue-cured tobacco leaves. Hyperspectral characteristic variables of ten physiological and biochemical indexes were found through stepwise regression, and SDr/SDb was the characteristic variable closest to seven biochemical contents. Simultaneously, the R2 and regression coefficient of equations reached 0.05 significant level and the equations had good estimating effects through the examination of other samples. Accordingly, this study suggested that the ten physiological and biochemical indexes could be estimated quickly by the estimating models, at the same time nitrogen-potassium fertilization and growth condition of flue-cured tobacco could be inspected.

The roles of microRNAs in regulating root formation and growth in plants

MicroRNAs(miRNAs) are small(ca. 20-24 nucleotides) non-coding RNAs that have recently been recognized as key post-transcriptional modulators of gene expression;and they are involved in many biological processes in plants, such as root growth and development. The miRNAs regulate root elongation, lateral root(LR) formation and adventitious root(AR) development in response to hormone signaling, nutrient uptake and biotic/abiotic stress. This review provides multiple perspectives on the involvement of miRNAs in regulating root growth and development in plants. We also discuss several crucial mechanisms of miRNAs, their relationships with transcription factors and the target gene-mediated hormone signaling interactions in the regulation of root growth and development.

Nutrient uptake,physiological responses and growth of tobacco(Nicotiana tabacum L.)in soil under composite salt stress

High soil salinity imposes osmotic stress and ion toxicity in plants,leading to substantial crop yield loss worldwide.Understanding of the quantitative and dynamic physiological responses to composite soil salt stress is limited and needs to be expanded.In this study,physiological,nutritional,and biomass yield parameters of tobacco(Nicotiana tabacum L.)grown in soil with five levels of composite soil salinity(CSS),basal CSS level(control,CK)and 3(T_(1)),6(T_(2)),9(T_(3)),and 12(T_(4))times the basal CSS level,under greenhouse were determined at days 30,60,and 90 after transplanting.Leaf dry biomass significantly(P<0.05)increased at the low salinity levels applied(T_(1) and T_(2))at all three time points,whereas it progressively declined as the CSS level further increased.The leaf physiological and photosynthetic responses were more adversely affected by CSS at the early growth stage(day 30).A path coefficient analysis demonstrated that leaf proline content had the largest direct effect(-0.66),and leaf Cu content had the most significant indirect effect(0.49)on leaf dry biomass of plants.The results suggest that lower CSS levels(T_(1) and T_(2))could stimulate tobacco growth(leaf biomass yield,in particular),and higher leaf proline and Cu levels at the early growth stage may potentially increase the ability of tobacco plants to withstand the adverse effects of salinity,which could be considered for future research and development of salinity management strategies.

Thymol ameliorates ammonium toxicity via repressing polyamine oxidase-derived hydrogen peroxide and modulating ammonium transporters in rice root

Background:Ammonium is an indispensable nutrient for crop growth,but anoxic conditions or inappropriate fertilizer usage result in the increase in ammonium content in soil.Excessive ammonium causes phytotoxicity.Thymol is a kind of natural phenolic compound with anti-microbial properties.However,little is known about the role of thymol in modulating plant physiology.Here we find the novel role of thymol in protecting rice from ammonium toxicity.Results:Thymol remarkably rescued rice seedlings growth from ammonium stress,which may resulted from the attenuation of reactive oxygen species(ROS)accumulation,oxidative injury,and cell death in both shoots and roots.Polyamine oxidase(PAO)metabolizes polyamines to produce ROS in plants in response to stress conditions.Thymol blocked ammonium-induced upregulation of a set of rice PAOs,which contributed to the decrease in ROS content.In rice seedlings upon ammonium stress,thymol downregulate the expression of ammonium transporters(AMT1;1 and AMT1;2);thymol upregulated the expression of calcineurin B-like interacting protein kinase 23(CIPK23)and calcineurin B-like binding protein 1(CBL1),two negative regulators of AMTs.This may help rice avoid ammonium overload in excessive ammonium environment.Correlation analysis indicated that PAOs,AMTs,and CBL1 were the targets of thymol in the detoxification of excessive ammonium.Conclusion:Thymol facilitates rice tolerance against ammonium toxicity by decreasing PAO-derived ROS and modulating ammonium transporters.Such findings may be applicable in the modulation of nutrient acquisition during crop production.