Reduced Shoot Growth Research Articles

Integration of seed priming with nano-sized chitosan-proline and biochar application improves salt tolerance in differentially responding genotypes of alfalfa (Medicago sativa)

Context Salinity is one of the major abiotic stresses challenging alfalfa (Medicago sativa) production. Aims In this study, we evaluated the potential of nano-sized chitosan-proline (NsCP) seed priming and biochar application to enhance salt tolerance in alfalfa. Methods Seeds of two alfalfa genotypes (OMA-84, salt-sensitive; and OMA-285, salt-tolerant) were soaked for 18 h in aerated distilled water (hydropriming) or a solution of NsCP (100 mM) for seed priming. Seeds were then planted in plastic pots containing acid-washed pure sand supplemented with or without biochar (25 g kg−1 sand) and with or without salt stress (120 mM). Key results Both genotypes showed significant reduction in root and shoot growth, biomass production, and carbon assimilation under salinity stress, with more pronounced effects on OMA-84. However, applying both NsCP seed priming and biochar significantly improved the biomass production and plant photosynthetic assessment traits. Notably, this combined approach proved more effective in enhancing salt tolerance than individual treatments. Biochar amendment increased the Na+ and Cl− concentration but it also contributed to salt tolerance by elevating K+ level, promoting proline accumulation, and antioxidant activities. Conclusions NsCP seed priming enhanced the salinity stress tolerance in alfalfa genotypes by facilitating osmotic adjustment (proline accumulation), maintaining ionic homeostasis (higher K+ and lower Na+ concentration), and increasing the levels of α-tocopherol, flavonoids, and the activities of antioxidant enzymes. Implications Integrated application of NsCP and biochar significantly enhanced salt tolerance in alfalfa, demonstrating practical strategies for sustainable agriculture in saline environments by promoting ionic homeostasis, osmotic adjustment, and antioxidant defence mechanisms.

Acclimatory responses of seed pretreatment to modulate organic acid production associated with Krebs’ cycle in NaCl-stressed legumes

Salinity hampers stand establishment of legumes at early growth stages that affect their yield. Seed pretreatment is an indispensable method for boosting tolerance to abiotic stresses and raising seed performance under salinity. Present study was aimed to evaluate whether seed pretreatment with mild dose of NaCl (sodium chloride) triggers ameliorative effects on growth and respiratory cycle of Cajanus cajan and Vigna mungo under salinity. Seedlings were raised hydroponically from non-pretreated and pretreated seeds under NaCl stress for three weeks. Non-pretreated Cajanus and Vigna seedlings exhibited reduction in root and shoot growth under salinity. Salt stress affected activities of enzymes associated with respiratory cycle specifically dehydrogenases, increased organic acid accumulation which played a versatile role to maintain cellular functions by balancing excess ions. Regardless of NaCl dose, the efficacy of seed pretreatment proved substantially beneficial to modulate the toxic effects of NaCl in both the test varieties. Lower perturbations of Krebs’ cycle in pretreated seedlings caused lower accumulation of organic acids due to prior seed acclimation conferring improved defence to thrive under salinity. Conclusively, since seed pretreatment contributes to minimize salt stress in both the test varieties, present study could be extended to legumes grown on soil to confirm the eco-friendly, cost-effective and ameliorative role of seed pretreatment to combat salt stress in saline prone agricultural fields.

Combined effects of climate stressors and soil arsenic contamination on metabolic profiles and productivity of rice (Oryza sativa L.).

Rice productivity and quality are increasingly at risk in arsenic (As) affected areas, challenge that is expected to worsen under changing climatic conditions. Free-Air Concentration Enrichment experiments revealed that eCO2, eO3, and eTemp, whether acting individually or in combination with low and high As irrigation, significantly impact rice yield and grain quality. Elevated CO₂ significantly increased shoot biomass, with minimal impact on root biomass, except under low As irrigation conditions. In contrast, eTemp alone reduced both shoot and root biomass, though the effect was not significant; eO₃ alone had little to no effect. Combined climatic stressors showed slight positive effects on growth. Under low As irrigation, eCO2 and eO3 promoted root growth but reduced shoot growth, while eTemp significantly suppressed both. High As irrigation exacerbated yield reductions, with the most severe decline observed under eTemp (66%), followed by eCO2 (48%), eO3 (36%), and their combination (35%). Arsenic irrigation, whether low or high, reduced macro and micronutrient concentrations in rice grains, with calcium being sole exception, remaining stable or even increasing. Sugar metabolites decreased under eCO2, eO3, and eTemp, but increased with As irrigation. Interestingly, climatic variables generally reduced grain As levels, high As irrigation combined with eCO2 exposure resulted in elevated grain As. This poses a dual concern: increased cancer risk due to As but potential benefit for individuals with diabetes, as the higher amylose content contributes to lower glycemic index. However, rice grown under high As irrigation exhibited significant nutritional imbalances, being rich in maltose and amylose but deficient in organic acids, phytosterols, fatty acids, organosilicons, and carboxylic acids. These findings underscore the dual threat of climate change and As contamination to rice productivity and quality. Developing resilient rice varieties with low grain As content is essential to ensure sustainable agricultural production and nutritional security in As affected regions.

Western corn rootworm resistance in maize persists in the absence of jasmonic acid.

Larva growth, survival, and development speed were not affected by the absence of jasmonic acid (JA) indicating that JA does not have a direct role in maize resistance to western corn rootworm. Jasmonic acid (JA) is a plant hormone that regulates multiple physiological processes including defense against herbivory by chewing insects. Previous research showed its importance for resistance to aboveground herbivory. While few studies have investigated the role of JA in resistance to belowground root-feeding herbivores, none has directly tested the role of JA in such resistance. In this study, we used an opr7opr8 double mutant to directly test the role of JA in resistance to western corn rootworm (Diabrotica virgifera virgifera, WCR), a devastating and specialist pest of maize. The opr7opr8 double mutant is deficient in JA accumulation as we found that it does not accumulate JA nor JA-Ile independently of exposure to WCR. We found no significant difference in growth (body mass), survival, and development of WCR larvae in response to JA deficiency, suggesting that disruption of JA biosynthesis does not impact resistance in maize roots to WCR. Additionally, we observed no significant effect on loss of root tissue caused by WCR associated with JA deficiency, while we found a reduction in shoot growth (mass) associated with WCR herbivory in the opr7opr8 mutant that was not observed in the wildtype. This suggested a role for JA in aboveground growth response to WCR herbivory rather than resistance to WCR.

In vitro slow-growth conservation, acclimatization, and genetic stability of virus-free apple plants

In vitro slow-growth storage has long played an important role in maintaining valuable horticultural materials. It is particularly applicable to the conservation of virus-free materials recovered from meristem culture or shoot-tip cryotherapy. In this study, the apple cultivar ‘Yanfu-6’ and the rootstock genotype ‘Qingzhen-1’ obtained from a virus disinfection program were compared during the establishment of in vitro slow-growth storage programs. At room temperature (25℃), combining with 4.5% sucrose or 0.5% mannitol, extended the conservation period of ‘Yanfu-6’ and ‘Qingzhen-1’to 5 and 9 months, respectively. Decreasing the temperature to 12℃ led to further reduced shoot growth, extending the conservation period to 9 months for ‘Yanfu-6’, while more than 80% of ‘Qingzhen-1’ shoots could be recovered after one year of storage. Similarly, high rooting and acclimatization success levels were obtained for ‘Qingzhen-1’ after one-year storage at 12℃, as well as for the plants that underwent monthly subcultures, but not for ‘Yanfu-6’. The inability to root in ‘Yanfu-6’ was overcome by micrografting onto rootstock ‘Qingzhen-1’, which resulted in a rooting percentage of 83% and an acclimatization success of 77%. In the analysis of genetic stability by next-generation sequencing, reduced levels of single nucleotide polymorphism (SNPs) and insertions and deletions (InDels) were detected in ‘Qingzhen-1’ shoots recovered after one-year storage at 12℃, as compared with shoots that underwent regular subcultures. These results highlight the use of in vitro slow-growth program assisted with micrografting for the conservation of valuable horticultural species.

Evaluation of Foxtail Millet Varieties for Thermotolerance at Seedling Stage using Temperature Induction Response Technique (TIR)

In the present scenario of climate change, Foxtail millet is the best crop of choice and an indispensable component of dryland farming due to its C4 plant type and tolerance against the abiotic stresses. However, all the foxtail millet varieties may not sustain under severe temperature stress particularly at germination and seedling growth stages. Therefore, screening of varieties is required to identify the stress tolerant varieties in foxtail millet which can combat temperature stress at seed germination and early seedling growth stages which is the need of the hour under ever changing climatic conditions. Hence, A lab experiment was conducted to standardize the temperature induction response (TIR) protocol for foxtail millet seedlings using WGC-450 programmable plant growth chamber. Temperatures were standardized as sub lethal i.e. challenging temperatures as 38°C – 54°C for 5 hours and lethal temperatures as 56°C for 3 hours. Seven foxtail millet varieties (Suryanandi, SiA 3156, Srilakshmi, SiA 3085, Narasimharaya, Krishnadevaraya and Prasad) were screened for intrinsic tolerance using the standardized Thermo Induced Response (TIR) protocol. Out of the seven varieties evaluated, SiA 3085, Prasad, Suryanandi, Srilakshmi were identified to possess high level of thermo tolerance in terms of higher seedling survival with less reduction in root and shoot growth. The varieties with intrinsic heat tolerance can be explored for the development of heat stress tolerant varieties.

Assessment of Sorghum (Sorghum bicolor L.) Genotypes for Temperature Tolerance Based on Temperature Induction Response (TIR) Technique

A novel temperature induction response (TIR) technique in Sorghum was standardized as sub lethal i.e. challenging temperatures of 38-56oC (for 5 hours) and lethal temperatures of 57oC (for 3 hours). Using this standardized TIR protocol, highly thermo tolerant genotypes were screened from 27 sorghum entries (parents and hybrids). Amongthem, 104A, M 35-1, PVK 801, 104 A x R 91012, 104 A x PVK 801, AKMS-66-2A x SPV 2758 and AKMS-66-2A x SPV 2468 showed the highest thermo tolerance ability in terms of 75.0 to 87.0 per cent seedlings survival and lower reduction in root and shoot growth. These entries have intrinsic heat tolerance and they can be explored as donor source in breeding programmes aimed.

Exploring the phytoremediation capacity of Portulaca oleracea naphthalene aromatic hydrocarbon contaminants: a physiological and biochemical study.

This study is aimed to explore the potential of purslane (Portulaca oleracea L.) as a phytoremediation candidate for the removal of naphthalene in a hydroponic system; moreover, the impacts of naphthalene on the physiological and biochemical characteristics of the plant were investigated. Four different naphthalene concentrations (0, 15, 30, and 60ppm) were selected for the experiments, with an additional control treatment without plants containing 60ppm naphthalene. Each treatment, utilizing a total of 20 hydroponic containers, consisted of 4 replicates. The results indicated that naphthalene led to a reduction in root and shoot growth. The root weight decreased from 17mg in the control group to 6mg in the 60ppm naphthalene treatment, while the shoot weight decreased from 107.5mg in the control group to 65.7mg in the 60ppm naphthalene treatment. Besides, the different naphthalene concentrations had an impact on the photosynthetic pigments. Compared to the control treatment, under severe stress conditions, chlorophyll a decreased by 51.85%, chlorophyll b decreased by 48.14%, and carotenoids decreased by 54.59%; however, anthocyanin, compared to the control treatment, increased by 30.1% under severe stress conditions. The presence of naphthalene also resulted in increased levels of malondialdehyde, hydrogen peroxide, and proline in both roots and shoots at various naphthalene concentrations. In roots, malondialdehyde increased by 40.74%, H2O2 increased by 3%, and proline increased by 75.6%, while malondialdehyde increased by 43.16%, H2O2 increased by 5.34%, and proline increased by 59.48% in shoots under severe stress conditions and compared to the control treatment. Root and shoot protein levels decreased by 64.49% and 32.26%, respectively. Furthermore, the antioxidant enzymes of glutathione S-transferase, superoxide dismutase, catalase, and ascorbate peroxidase showed increased activities in both roots and shoots under severe naphthalene stress conditions. Purslane demonstrated the ability to remove approximately 80% of naphthalene from the medium. In conclusion, this plant has an effective participation in naphthalene uptake and mitigates the adverse effects of naphthalene by enhancing antioxidant enzyme and proline activities.

Salicylic acid and iron-oxide nanoparticles improved the growth and productivity of ajowan under salt stress

Two factorial experiments with randomized complete block design in three replicates were conducted in a greenhouse at the University of Tabriz to investigate the individual and combined effects of SA and Fe2O3-NPs spray (1 mM and 3 mM, respectively) on cations contents, root and shoot growth, seed filling and yield parameters of salt-stressed ajowan plants (0, 4, 8 and 12 dS m-1 NaCl; as non-saline and low, moderate and high salinities, respectively). Salt stress enhanced Na+ contents and reduced K+ and Ca2+ contents, and K+/Na+ and Ca2+/Na+ ratios, leading to a reduction in root and shoot growth, particularly under high salinity. Reduction in plant growth parameters under salt stress had a negative impact on yield components and seed yield of ajowan. These deleterious impacts of salinity on plants were largely overcome by foliar treatments, particularly by SA + Fe2O3-NPs. The improvement of seed yield by these treatments was highly correlated with enhanced root and shoot growth, seeds per plant, and 1000-seed weight, especially under moderate and high salinities. Thus, the simultaneous application of SA and Fe2O3-NPs was the best foliar treatment for enhancing the growth and productivity of ajowan plants under normal and saline conditions.

The Optimum Substrate Moisture Level to Enhance the Growth and Quality of Arugula (Eruca sativa)

Arugula (Eruca sativa Mill.) is a nutritious vegetable, commonly used in salads, known for its high glucosinolate content and various health benefits and flavors. However, arugulas may contain -excessive nitrate levels, potentially harmful to human health. We aimed to examine the effect of substrate moisture levels on the growth and quality of arugula under controlled irrigation conditions to investigate a proper irrigation practice for the quality production of arugula. The plants were cultivated using a sensor-based automated irrigation system to maintain the substrate volumetric water content (VWC) levels at 0.20, 0.30, 0.40, and 0.50 m3·m−3 over three weeks (vegetative stage). The treatment with VWC of 0.20 m3·m−3 resulted in reduced shoot growth, primarily attributed to drought-induced constraints on leaf expansion. Despite the initial reductions in stomatal conductance in arugulas subjected to lower VWC treatments, they eventually recovered and exhibited similar stomatal conductance levels across all VWC treatments 15 days after treatment, indicating acclimation to drought stress. The VWC treatment did not affect the nitrate and total glucosinolate contents of arugula, except for a decrease in glucoerucin content observed in the lowest VWC treatment. Maintaining a VWC level at 0.20 m3·m−3 could impair both the growth and quality of arugula due to severe drought conditions. Alternatively, maintaining the VWC at 0.30 m3·m−3 would ensure a high water use efficiency while securing the growth and quality of arugula.

Chickpea (Cicer arietinum) PHO1 family members function redundantly in Pi transport and root nodulation

Phosphorus (P), a macronutrient, plays key roles in plant growth, development, and yield. Phosphate (Pi) transporters (PHTs) and PHOSPHATE1 (PHO1) are central to Pi acquisition and distribution. Potentially, PHO1 is also involved in signal transduction under low P. The current study was designed to identify and functionally characterize the PHO1 gene family in chickpea (CaPHO1s). Five CaPHO1 genes were identified through a comprehensive genome-wide search. Phylogenetically, CaPHO1s formed two clades, and protein sequence analyses confirmed the presence of conserved domains. CaPHO1s are expressed in different plant organs including root nodules and are induced by Pi-limiting conditions. Functional complementation of atpho1 mutant with three CaPHO1 members, CaPHO1, CaPHO1;like, and CaPHO1;H1, independently demonstrated their role in root to shoot Pi transport, and their redundant functions. To further validate this, we raised independent RNA-interference (RNAi) lines of CaPHO1, CaPHO1;like, and CaPHO1;H1 along with triple mutant line in chickpea. While single gene RNAi lines behaved just like WT, triple knock-down RNAi lines (capho1/like/h1) showed reduced shoot growth and shoot Pi content. Lastly, we showed that CaPHO1s are involved in root nodule development and Pi content. Our findings suggest that CaPHO1 members function redundantly in root to shoot Pi export and root nodule development in chickpea.

The effect of root shaving and biostimulant application on the transplant success of six common Australian urban tree species

To enhance the establishment of container-grown trees, nursery and urban forest practitioners use root pruning to improve plant root structure. However, some methods of root pruning may cause stress to the plant and reduce shoot growth. One potential approach to mitigating tree stress is the application of biostimulants. This study aimed to determine the impact root shaving, a type of root pruning, has on the growth of urban plant species, and whether biostimulant application mitigates this impact. To address these aims, we applied root shaving (not shaved, shaved) and biostimulant (control, humic substance, protein hydrolysate, seaweed extract) treatments to six tree species that are commonly planted in the Sydney metropolitan area, Australia in a factorial design. The study consisted of a glasshouse and field experiment to simulate nursery production and urban field conditions, respectively. We found that the assimilation rate of the plants was not affected by root shaving but four of the species still experienced reductions in shoot growth in the short-term. This reduction was a result of the plants allocating resources to root growth to compensate for the root loss. However, in the long-term, the plants were able to compensate for this reduction in shoot growth. We found that biostimulant application did not mitigate the short-term impacts of root shaving on plant growth. We can conclude that root shaving and biostimulant application do not affect plant establishment in the long-term.

Differential accumulation of phenolics and phytoalexins in seven Malus genotypes cultivated in apple replant disease-affected soil

Apple replant disease (ARD) is a globally recognised soil-borne disease, which affects apple orchards and tree nurseries. Biotic factors are considered to be the main causal agent of ARD. Phenolics and phytoalexins were induced in apple roots grown in ARD soil compared to roots grown in disinfested ARD soil. However, the relationship between ARD susceptibility and production of phenolics and phytoalexins in apple roots is still unclear. To answer this question, we cultivated seven Malus genotypes with varying levels of ARD susceptibility (M.26, EMR 2, M.200, G.214, G.935, Selection 4, and MAL0739) in both ARD soil from Heidgraben, Germany, and the same soil after disinfestation by gamma-irradiation (γ-ARD). Despite the overall growth reduction observed for all seven genotypes, three of them, EMR 2, G.935 and MAL0739, showed better performance, as indicated by the ARD susceptibility index (ASI) and differences in their root structure. Phenolics and phytoalexins were differentially induced in the roots grown for four weeks (T4) and eight weeks (T8) in ARD soil compared to γ-ARD soil. Moreover, differences in the total phenolics content (TPC) and the total phytoalexin content among the evaluated Malus genotypes were observed. The biochemical data from the early time point (T4) separated Malus genotypes more effectively compared to that from the late time point (T8). Among the six ARD-induced phytoalexins, 3-hydroxy-5-methoxybiphenyl at T4 can serve as an early biomarker for ARD. Although TPC and total phytoalexin content of the Malus genotypes exhibited no or weak correlation with root and shoot growth reduction, some individual phenolics and phytoalexins showed higher coefficients, suggesting that they might influence the ARD susceptibility of apple rootstocks.

Effect of NaCl on physiological, biochemical, and ionic parameters of naked oat (Avena nuda L.) line Bayou1

Oat (Avena nuda L.) is a globally important cereal crop grown for its nutritious grains and is considered as moderately salt-tolerant. Studying salinity tolerant mechanisms of oats could assist breeders in increasing oat production and their economic income in salt-affected areas, as the total amount of saline land in the world is still increasing. The present study was carried out to better understand the salt tolerance mechanism of the naked oat line Bayou1. A soil experiment was conducted on 17 days-old Bayou1 seedlings treated with varying concentrations of NaCl for a period of 12 days. Bayou1 plants grew optimally when treated with 50 mM NaCl, demonstrating their salinity tolerance. Reduced water uptake, decreased Ca2+, Mg2+, K+, and guaiacol peroxidase activity, as well as increased Na+ concentration in leaves, all contributed to a reduction in shoot growth. However, the damage to ionic homeostasis caused by increased Na+ concentrations and decreased K+ concentrations in the roots of Bayou1 did not inhibit its root growth, indicating that the main salt-tolerant mechanism in Bayou1 existed in its roots. Further, a hydroponic experiment found that increasing Na+ concentration in root cell sap enhanced root growth, while maintaining the integrity of root cell membranes. The accumulated Na+ may have facilitated the root growth of Bayou1 exposed to NaCl by effectively adjusting cellular osmotic potential, thereby ensuring root cell turgor and expansion.

Brief characterisation of Fe chlorosis in chia (Salvia hispanica L.) plants grown in nutrient solution

ABSTRACT Chia (Salvia hispanica L.) plant is a well-known plant due to the nutraceutical value of its seeds. The aim of this preliminary study was to assess the response of Chia plants to Fe deficiency. Chia plants were grown for 12 days in Hoagland’s nutrient solutions without Fe (Fe0) and with Fe (Fe10-10 µM Fe). Biomass parameters and root ferric chelate-reductase activity (FC-R; EC 1.16.1.17) were determined at the end of the experiment. Chlorophyll estimations (expressed as SPAD readings) decreased progressively, showing the typical symptoms of iron chlorosis. In addition, iron-deficient chia plants exhibit smaller biomass (number of leaves, root, and shoot growth reduction) compared to control plants. These plants also showed morphological changes in roots. Furthermore, root FC-R activity was significantly lower in Fe0 plants.

The problem of soil fatigue in apple orchardsmonoculture

The article provides an analysis of current domestic and foreign scientific sources regarding the phenomenon of soil depletion in perennial apple orchards, its impact on the growth and productivity of apple trees, and measures to improve the soil’s ecological condition within monocultures. In recent years, there has been an increasing need to establish new apple plantations on land plots after the removal of old orchards. This is influenced by various factors, including the cultivation of intensive short-cycle orchards with necessary infrastructure, economic facilities with access networks situated on privatized lands, the designated use of which cannot be altered. Consequently, establishing new fruit plantations on land previously unused for perennial fruit crops becomes unfeasible. This underscores the necessity of enhancing soil quality indicators, including reducing or entirely mitigating the negative effects of soil depletion on young trees following the removal of old ones. Particular attention is warranted to the adverse impact of cultivating weak-growing varieties on dwarf rootstocks repeatedly. These root systems are located in surface layers of the soil where the majority of the roots from previously grown trees were concentrated. A series of studies have demonstrated the negative influence on plant growth indicators when young trees are grown in the same location as removed orchards. The presence of residual tree roots in the soil suppresses the growth of young plantations, leading to a reduction in stem diameter, shoot growth, and tree height. In global practice, fumigation (chemical and biological), cultivation of specific plant species in interrows for bioremediation with subsequent plowing as cover crops, the application of mineral and organic fertilizers, various biostimulants, and organic additives are often used to minimize the negative effects of soil depletion. Continuous research is being conducted to study various crop varieties, fertilization systems, and agricultural practices aimed at effectively and ecologically safely addressing the issue of soil depletion in specific soil-climatic conditions.

Organ-specific responses during acclimation of mycorrhizal and non-mycorrhizal tomato plants to a mild water stress reveal differential local and systemic hormonal and nutritional adjustments

Main conclusionTomato plant acclimation to a mild water stress implied tissue-specific hormonal and nutrient adjustments, being the root one of the main modulators of this response.Phytohormones are key regulators of plant acclimation to water stress. However, it is not yet clear if these hormonal responses follow specific patterns depending on the plant tissue. In this study, we evaluated the organ-specific physiological and hormonal responses to a 14 day-long mild water stress in tomato plants (Solanum lycopersicum cv. Moneymaker) in the presence or absence of the arbuscular mycorrhizal fungus Rhizoglomus irregulare, a frequently used microorganism in agriculture. Several physiological, production, and nutritional parameters were evaluated throughout the experiments. Additionally, endogenous hormone levels in roots, leaves, and fruits at different developmental stages were quantified by ultrahigh-performance liquid chromatography coupled to tandem mass spectrometry (UHPLC–MS/MS). Water deficit drastically reduced shoot growth, while it did not affect fruit production. In contrast, fruit production was enhanced by mycorrhization regardless of the water treatment. The main tissue affected by water stress was the root system, where huge rearrangements in different nutrients and stress-related and growth hormones took place. Abscisic acid content increased in every tissue and fruit developmental stage, suggesting a systemic response to drought. On the other hand, jasmonate and cytokinin levels were generally reduced upon water stress, although this response was dependent on the tissue and the hormonal form. Finally, mycorrhization improved plant nutritional status content of certain macro and microelements, specially at the roots and ripe fruits, while it affected jasmonate response in the roots. Altogether, our results suggest a complex response to drought that consists in systemic and local combined hormonal and nutrient responses.

Biometric and morphological adjustments of Eugenia. dysenterica DC. seedlings in response to increased soil water deficit

Water stress can affect all aspects of plant growth and development, compromising its productive potential. The cultivation of fruit species native to the Cerrado and the study of their behavior under conditions of low water availability are necessary activities, in view of their socioeconomic and environmental potential. This study was conducted to evaluate the effect of water deficit on growth and biomass production of the cagaita tree (Eugenia dysenterica DC.), a species endemic to the Cerrado (Brazilian Savannah). The experiment was performed in a greenhouse for 120 days in a randomized block design (RBD), with a double factorial arrangement (2x5), corresponding to two cagaita mother plants and five water conditions. We evaluated the growth and leaf, stem and root functional characteristics. The most severe water deficit conditions reduced shoot growth, number of leaves, production of biomass and dry matter and increased the specific and per plant mass root length of cagaita plants. Deficit extension had negative effects on its growth and development. There was a statistical difference between mother plants, with mother plant 2 being more resistant to drought. The application of a severe or longer water deficit affected shoot growth and reduced the appearance of new leaves. The stress caused by water deficiency allowed an increase in root functional characteristics, supporting the hypothesis that plants under adverse conditions focus on higher biomass production and convert a higher amount of dry matter into the roots. Leaf area did not show to be a functional characteristic, explaining the stress effects in E. dysenterica DC plants.

Deficit Irrigation Applied to Lemon Trees Grafted on Two Rootstocks and Irrigated with Desalinated Seawater.

The use of desalinated seawater (DSW) for irrigation in semi-arid regions is taking hold. Citrus tolerance to ions that predominate in DSW and water stress depends on the rootstock. Deficit irrigation was applied to DSW-irrigated lemon trees and grafted on rootstocks with different tolerance (Citrus macrophylla (CM) and sour orange (SO)). Plants were irrigated with DSW or Control treatment (distilled water), and, 140 days later, irrigation treatments were started: full irrigation (FI) or DI (50% of the volume applied to FI). After 75 days, differences between CM and SO plants irrigated with DSW and under DI were found. The higher concentrations of Cl- and Na+ in CM and B in SO were the main causes of shoot growth reduction. The osmotic adjustment of CM plants was made possible by the accumulation of Na+, Cl-, and proline, but SO failed to adjust osmotically. In CM and SO plants, photosynthesis reduction was due to lower chlorophyll levels, but also to stomatal factors (CM plants) or alterations of the photochemical machinery (SO plants). Finally, unlike CM, SO had a good antioxidant system. In the future, knowing the different responses of CM and SO under these stressful conditions could be useful in citrus-growing areas.

Seed priming with rutin enhances tomato resistance against the whitefly Bemisia tabaci

Flavonoids are ubiquitously distributed in plants, showing pleiotropic effects in defense against abiotic and biotic stresses. Although it has been shown that seed priming with flavonoids can enhance plant resistance to abiotic stress, little is known about its potential to enhance plant tolerance to biotic stresses, especially for herbivorous insects. Here, we investigated whether treatment of tomato (Solanum lycopersicum) seeds with rutin improves plant resistance against the whitefly (Bemisia tabaci). Specifically, we measured the effect of rutin seed treatment on tomato seedling vigour, plant growth, feeding behavior and performance of B. tabaci on plants grown from control and rutin-treated seeds, and plant defense responses to B. tabaci attack. We found that seed treatment with different concentrations of rutin (viz 1, 2, 5, 10, and 20 mM) had minimal impact on shoot growth. Furthermore, seed treatment of rutin reduced the developmental rate of nymphs, the fecundity and feeding efficiency of adult females on plants grown from these seeds. The enhanced resistance of tomato against B. tabaci is closely associated with increased flavonoids accumulation, callose deposition and the expression of jasmonic acid (JA)-dependent defense genes. Additionally, callose deposition and expression of JA-dependent genes in tomato plants grown from rutin-treated seeds significantly increased upon B. tabaci infestation. These results suggest that seed treatment with rutin primes tomato resistance against B. tabaci, and are not accompanied by reductions in shoot growth. Defense priming by seed treatments may therefore be suitable for commercial exploitation.