Tomato Root Response to Subsurface Drip Irrigation

Four depth treatments of subsurface drip irrigation pipes were designated as 1) at 20,2) 30 and 3) 40 cm depths all with a drip-proof flumes underneath,and 4) at 30 cm without a drip-proof flume to investigate the responses of a tomato root system to different technical parameters of subsurface drip irrigation in a glass greenhouse,to evaluate tomato growth as affected by subsurface drip irrigation,and to develop an integrated subsurface drip irrigation method for optimal tomato yield and water use in a glass greenhouse. Tomato seedlings were planted above the subsurface drip irrigation pipe. Most of the tomato roots in treatment 1 were found in the top 0-20 cm soil depth with weak root activity but with yield and water use efficiency (WUE) significantly less (P ---- 0.05) than treatment 2; root activity and tomato yield were significantly higher (P = 0.05) with treatment 3 compared to treatment 1; and with treatment 2 the tomato roots and shoots grew harmoniously with root activity,nutrient uptake,tomato yield and WUE significantly higher (P= 0.05) or as high as the other treatments. These findings suggested that subsurface drip irrigation with pipes at 30 cm depth with a drip-proof flume placed underneath was best for tomato production in greenhouses. In addition,the irrigation interval should be about 7-8 days and the irrigation rate should be set to 225 m3 ha-1 per event.

OsABA8ox2, an ABA catabolic gene, suppresses root elongation of rice seedlings and contributes to drought response

In rice, OsABA8ox encodes abscisic acid(ABA) 8′-hydroxylase, which catalyzes the committed step of ABA catabolism. The contribution of ABA catabolism in root development remains unclear. We investigated the role of OsABA8ox2 in root growth and development and drought response. GUS staining results showed that OsABA8ox2 was expressed mainly in roots at seedling stage and was strongly expressed in the meristematic zone of the radicle. OsABA8ox2 expression in roots was markedly decreased after 0.5 h polyethylene glycol(PEG) treatment and increased after 0.5 h rehydration, implying that OsABA8ox2 is a drought-responsive gene.OsABA8ox2 knockout mediated by the CRISPR-Cas9 system increased drought-induced ABA and indole-3-acetic acid accumulation in roots, conferred increased ABA sensitivity, and promoted a more vertically oriented root system architecture(RSA) beneficial to drought tolerance.OsABA8ox2 overexpression suppressed root elongation and increased stomatal conductance and transpiration rate. Consequently, OsABA8ox2 knockout dramatically improved rice drought tolerance, whereas OsABA8ox2 overexpression seedlings were hypersensitive to drought stress,suggesting that OsABA8ox2 contributes to drought response in rice. Compared with wild type,functional leaves of OsABA8ox2 knockout seedlings showed higher ABA levels, whereas overexpression lines showed lower ABA levels, suggesting that OsABA8ox2, as an ABA catabolic gene, modulates ABA concentration through ABA catabolism. OsABA8ox2 and OsABA8ox3 were both localized in the endoplasmic reticulum. Together, these results indicate that OsABA8ox2 suppresses root elongation of rice seedlings, increases water transpiration, and contributes to drought response through ABA catabolism, and that OsABA8ox2 knockout dramatically improves rice drought tolerance. They highlight the key role of ABA catabolism mediated by OsABA8ox2 on root growth and development. OsABA8ox2, as a novel RSA gene, would be a potential genetic target for the improvement of rice drought tolerance.

Effect of Mineral Acids on Rooting Response of Aging Mung Bean （Phaseolus aureus Roxb,） Cuttings via Indole Acetic Acid Level

The influence of nitric acid （HNO3） as a strong mineral acid on rooting response of fresh mad aging mung bean cuttings has been studied on the level of Indole-3-Acetic Acid （IAA）. The data revealed significant increase in rooting response of fresh cuttings treated with （0.0001% and 0.1%） concentrations of HNO3 solution, significant increase in rooting response of aged cuttings （for 3 days in d/H20） with （0.0001% and 0.01%） concentration of HNO3 solution and highly significant increase in rooting response of aged cuttings （for 3 days in HNO3 solution） with （0.0001%） concentration, while highly concentration （0.5%） revealed highly significant decrease in rooting response compared to control （d/H20）. Quantitative estimation oflAA by spectrophotometric method as indicators for oxidative processes that occurrence during aging phenomenon verified a highly significant increase of IAA content in hypocotyles of fresh and aged cuttings in optimal concentration of HNO3.

MicroRNAs associated with molecular mechanisms for plant root formation and growth

Although roots are so important for plant growth and crop productivity, the molecular mecha- nism（s） of root formation and growth is not fully under- stood. To increase our understanding of the underlying molecular mechanisms, here we review microRNA regu- lation of processes related to root formation： the regulation of transcription factors, nutrient uptake, stress signaling, and growth signaling. We have summarized the interaction, expression, transport, and signaling events that involve microRNAs in ideal and stressed conditions in a number of model plants, highlighting the involvement of microRNAs in root formation. MicroRNAs are now known to be important players in root initiation, development, and growth; understanding the precise mechanisms involved will be valuable for plant molecular breeding to develop high-yielding crops with high stress resistance and low nutrient requirements.

Seismic Response of Base-Isolated Structures underMulti-component Ground Motion Excitation

An analysis of a base-isolated structure for multi-component random ground motion is presented. The mean square respond of the system is Obtained under different parametric variations. The effectiveness of main parameters and the torsional component during an earthquake is quantified with the help of the response ratio and the root mean square response with and without base isolation. It is observed that the base isolation has considerable influence on the response and the effect of the torsional component is not ignored.

Potassium channel AKT1 is involved in the auxin-mediated root growth inhibition in Arabidopsis response to low K^+stress

The changes in external K^＋ concentration affect plant root growth. However, the molecular mechanism for perceiving a K^＋ signal to modulate root growth remains unknown. It is hypothesized that the K^＋ channel AKTI is involved in low K^＋ sensing in the Arabidopsis root and subsequent regulation of root growth. Along with the decline of external K^＋ concentration, the primary root growth of wild-type plants was gradually inhibited. However, the primary root of the akt1 mutant could still grow under low K^＋（LK） conditions. Application of NAA inhibited akt1 root growth, but promoted wild-type root growth under LK conditions. By using the ProDR5：GFP and ProPIN1：PIN1-GFP lines, we found that LK treatment reduced auxin accumulation in wild-type root tips by degrading PIN1 proteins, which did not occur in the akt1 mutant. The LK-induced PIN1 degradation may be due to the inhibition of vesicle trafficking of PIN1 proteins. In conclusion, our findings indicate that AKT1 is required for an Arabidopsis response to changes in external K^＋, and subsequent regulation of K^＋-dependent root growth by modulating PINt degradation and auxin redistribution in the root.

Dynamics of one-prey two-predator system with square root functional response and time lag

Animals grouping together is one of the most interesting phenomena in population dynamics and different functional responses as a result of prey-predator forming groups have been considered by many authors in their models. In the present paper we have considered a model for one prey and two competing predator populations with time lag and square root functional response on account of herd formation by prey. It is shown that due to the inclusion of another competing predator, the underlying system without delay becomes more stable and limit cycles do not occur naturally. However, after considering the effect of time lag in the basic system, limit cycles appear in the case of all equilibrium points when delay time crosses some critical value. From the numerical simulation, it is observed that the length of delay is minimum when only prey population survives and it is maximum when all the populations coexist.

Blue Light-Triggered Chemical Reactions Underlie Phosphate Deficiency-Induced Inhibition of Root Elongation oM/ab/dops/s Seedlings Grown in Petri Dishes

To tolerate phosphate(Pi)deficiency in the environment,plants alter their developmental and metabolic programs.In the past two decades,researchers have extensively used Petri dish-grown seedlings of the model plant Arabidopsis thaliana to study the molecular mechanisms underlying root developmental responses to Pi deficiency.A typical developmental response of the Petri dish-grown Arabidopsis seedlings to Pi deficiency is the inhibited growth of primary root(PR).This response is generally thought to enhance the production of lateral roots and root hairs,which increases the plant’s ability to obtain Pi and is therefore regarded as an active cellular response.Here,we report that direct illumination of root surface with blue light is critical and sufficient for Pi deficiency-induced inhibition of PR growth in Arabidopsis seedlings.We further show that a blue light-triggered malate-mediated photo-Fenton reaction and a canonical Fenton reaction form an Fe redox cycle in the root apoplast.This Fe redox cycle results in the production of hydroxyl radicals that inhibit PR growth.In addition to revealing the molecular mechanism underlying Pi deficiency-induced inhibition of PR growth,our work demonstrated that this developmental change is not an active cellular response;instead,it is a phenotype resulting from root growth in transparent Petri dishes.This finding is significant because illuminated,transparent Petri dishes have been routinely used to study Arabidopsis root responses to environmental changes.