Sowbiya Muneer

Silicon alleviates salt stress by modulating antioxidant enzyme activities in Dianthus caryophyllus ‘Tula’

Although silicon (Si) is not considered as an essential element, it is beneficial to the plant growth. Its effect is more evident under abiotic and biotic stress conditions. The objective of this study is to investigate the role of Si on the in vitro growth and resistance to salt stress of Dianthus caryophyllus ‘Tula’. The experiment was designed as a factorial design with 0, 50, or 100 mg·L−1 of potassium silicate (K2SiO3) in combination with 0, 50, or 100 mM sodium chloride (NaCl). The treatment of 50 mg·L−1 Si improved the growth of plant. However, the treatment of Si at 100 mg·L−1 reduced the growth. Although NaCl retarded the growth, addition of Si along with NaCl to the culture medium mitigated the effect of NaCl. A primary defense line by Si to overcome the photosynthetic depression was apparent from the increased chlorophyll content in the Si + NaCl treatment as compared to the treatment of NaCl alone. Enhancement of growth and resistance to salinity by Si was thought to be due to the modulation in activity of antioxidant enzymes, such as superoxide dismutase, ascorbate peroxidase, guaiacol peroxidase, and catalase. Therefore, our results suggested that 50 mg·L−1 Si supplementation could be optimal for improved growth in vitro and enhanced resistance against salinity in D. caryophyllus ‘Tula’.

Proteomic and Antioxidant Analysis Elucidates the Underlying Mechanism of Tolerance to Hyperhydricity Stress in In Vitro Shoot Cultures of Dianthus caryophyllus

Hyperhydric disorders occur frequently in plant tissues cultured in vitro and cause several morphological and physiological abnormalities. However, a systematic defense response is triggered by hyperhydric conditions. The accumulation of reactive oxygen species (ROS), activities of antioxidant enzymes and their immunoblots, and the proteome-level changes in normal versus hyperhydric shoots of carnation (Dianthus caryophyllus) cultured in vitro were investigated. Total proteins were also extracted from the shoot and analyzed by two-dimensional electrophoresis. Among a total of 700 spots detected, only 40 had significant changes in abundance in the hyperhydric compared to the normal shoots, which were further identified by a mass spectrometer (MALDI-TOF MS). Most of them were involved in photosynthesis, RNA processing, and general metabolisms, while the rest were involved in secondary metabolic processes. These identified proteins in carnation shoots may provide novel evidences for stress tolerance against hyperhydricity.

Proteomic Analysis Provides New Insights in Phosphorus Homeostasis Subjected to Pi (Inorganic Phosphate) Starvation in Tomato Plants (Solanum lycopersicum L.).

Phosphorus is a major nutrient acquired by plants via high-affinity inorganic phosphate (Pi) transporters. To determine the adaptation and homeostasis strategy to Pi starvation, we compared the proteome analysis of tomato leaves that were treated with and without Pi (as KH2PO4) for 10 days. Among 600 reproducible proteins on 2-DE gels 46 of them were differentially expressed. These proteins were involved in major metabolic pathways, including photosynthesis, transcriptional/translational regulations, carbohydrate/energy metabolism, protein synthesis, defense response, and other secondary metabolism. The results also showed that the reduction in photosynthetic pigments lowered P content under –Pi treatments. Furthermore, high-affinity Pi transporters (lePT1 and lePT2) expressed in higher amounts under –Pi treatments. Also, the accumulation of Pi transporters was observed highly in the epidermis and palisade parenchyma under +Pi treatments compared to –Pi treatments. Our data suggested that tomato plants developed reactive oxygen species (ROS) scavenging mechanisms to cope with low Pi content, including the up-regulation of proteins mostly involved in important metabolic pathways. Moreover, Pi-starved tomato plants increased their internal Pi utilization efficiency by increasing the Pi transporter genes and their rational localization. These results thus provide imperative information about how tomato plants respond to Pi starvation and its homeostasis.

Red and Blue Light Emitting Diodes (LEDs) Participate in Mitigation of Hyperhydricity in In Vitro-Grown Carnation Genotypes (Dianthus Caryophyllus)

The present study was to determine the factors that can reduce hyperhydricity in in vitro-propagated carnation genotypes. The carnation genotypes (Green Beauty, Purple Beauty, and Inca Magic) were grown in vitro under normal and hyperhydric conditions in white fluorescent light (FL) in which half of the hyperhydric plants were grown in red and blue LEDs (light emitting diodes). It was observed that hyperhydricity leads to oxidative stress in terms of TBARS (thiobarbituric acid reactive substances) content, whereas stress was alleviated by R (red) and B (blue) LEDs. The multiprotein complex proteins such as ATPase (RCI + LHC1) PSII-core dimer, PSII-monomer/ATPs synthase, and PSII-monomer/cyt b6f had decreased levels in hyperhydric conditions grown in white FL; however, the expression level of these photosynthetic proteins was retained in hyperhydric plants grown in R and B LEDs. Moreover, the immunoblots of two photosynthetic proteins (PsaA and PsbA) and stress-responsive proteins such as superoxide dismutase, ascorbate peroxidase, and catalase showed recovery of hyperhydricity in carnation genotypes grown in R and B LEDs. Our present study signifies that red (R) and blue light (B) LEDs reduced the hyperhydricity to control levels by maintaining the composition of thylakoid proteins and antioxidative defense mechanisms in carnation genotypes.

Foliar or Subirrigation Silicon Supply Mitigates High Temperature Stress in Strawberry by Maintaining Photosynthetic and Stress-Responsive Proteins

Silicon (Si) is the second most abundant element in the soil and is known to help in crop productivity. Si improves photosynthesis as well as remediates nutrient imbalances and abiotic stresses in plants. The impact and the importance of different sources, concentration, and supply of Si in improving the propagation of horticultural crops are limited. Thus, the present study focused on the supply, concentration, and source of Si on two important Korean strawberry cultivars ‘Sulhyang’ and ‘Maehyang’ under temperature stress. The high temperature (41 °C) resulted in oxidative stress in the form of H2O2 and O21− localizations in the -Si- and Si-treated plants as compared to 25 or 33 °C in both cultivars. However, Si, especially that from K2SiO3 source, had the ability to relieve the stress level. The immunoblots of two important photosynthetic proteins PsaA and PsbA showed decreased expression levels in the -Si plants under 41 °C temperature stress, whereas the expression levels were retained in the Si-supplied plants, particularly with K2SiO3 as the Si source. In both 25 and 33 °C, no changes in expressions of PsaA and PsbA were observed. Interestingly, the expression of three important stress-responsive proteins, superoxide dismutase (SOD), ascorbate peroxidase (APX), and catalase (CAT), were abundantly increased in the Si-treated plants under high-temperature stress (41 °C) and decreased in the –Si-treated plants except in those grown in 25 or 33 °C. The observed responses to silicon supply in high temperature stressed-plants indicate that Si, particularly in the form of K2SiO3, has a significant role in limiting the negative effects of high temperature stress by maintaining the photosynthetic proteins and stress-responsive proteins of the ascorbate glutathione defense mechanism. Moreover, these results also depict that Si application is a good way to maintain the health of plants at the propagation stage even under high temperatures of greenhouses.

Silicon-mediated enhancement of physiological and biochemical characteristics of Zinnia elegans ‘Dreamland Yellow’ grown under salinity stress

This study investigated the effects of silicon (Si) nutrition on hydroponically grown Zinnia elegans under salinity stress. In this study, six treatments, the control (basal nutrients without NaCl or Si), Si 50 (1.8 mM), Si 100 (3.6 mM), NaCl 50 (50 mM), Si 50 + NaCl 50 (1.8 mM Si; 50 mM NaCl), and Si 100 + NaCl 50 (Si-3.6 mM + NaCl-50 mM), were employed. After 15 days of treatment, growth parameters, biochemical measurements, and antioxidant enzyme activities were examined. Salinity stress significantly reduced plant growth, biomass, photosynthetic parameters, and pigments, and increased the electrolyte leakage potential (ELP), lipid peroxidation, and hydrogen peroxide level. Interestingly, with Si supplementation, Z. elegans recovered from salinity stress. Si enhanced growth and photosynthesis, and prevented the decomposition of photosynthetic pigments. Moreover, the addition of Si increased membrane integrity, thereby reducing the ELP and lipid peroxidation levels under salinity stress. Furthermore, Si modulated the activity of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and guaiacol peroxidase (GPX) in scavenging excess reactive oxygen species (ROS). Additionally, Si increased the macronutrient and micronutrient contents. Therefore, augmentation with Si provided salinity resistance and enhanced the growth of Z. elegans.

Light quality during night interruption affects morphogenesis and flowering in Petunia hybrida, a qualitative long-day plant

We investigated the effects of light quality during night interruption (NI) on morphogenesis, flowering, and the transcription of photoreceptor genes in Petunia hybrida Hort. ‘Easy Wave Pink’ (a qualitative long-day plant, LDP). Plants were grown in a closed-type plant factory under a constant light intensity of 180 μmol·m-2·s-1 PPF provided by white (W) light emitting diodes (LEDs) under long day (LD, 16 h light/8 h dark), short day (SD, 10 h light/14 h dark), or SD conditions with a 4 h NI using green (NI-G), blue (NI-B), red (NI-R), far-red (NI-Fr), or white (NI-W) LEDs at an intensity of 10 μmol·m-2·s-1 PPF. Shoot length was greatest under NI-Fr. Flowering was observed under LD, NI-G, NI-Fr, and NI-W. The expression of photoreceptor genes was induced by NI. Specifically, phyA, phyB, and cry1 were more highly expressed under NI-G, NI-B, and NI-R compared to LD and SD. These results suggest that morphogenesis, flowering, and transcriptional factors are strongly affected by light quality during NI.

Light quality during night interruption affects morphogenesis and flowering in geranium

We investigated the effects of light quality during night interruption (NI) on morphogenesis, flowering, and the transcription of photoreceptor genes in the geranium Pelargonium × hortorum L.H. Bailey ‘Ringo 2000 Violet’ (day neutral plant, DNP). Plants were grown in an environment-controlled chamber under a constant light intensity of 180 μmol·m-2·s-1 PPF. The light was supplied by white (W) light emitting diodes (LEDs) to create long day (LD, 16 h light/8 h dark), short day (SD, 10 h light/14 h dark), or SD with a 4 h night interruption (NI) conditions. The NI was provided by green (NI-G), blue (NI-B), red (NI-R), far-red (NI-Fr), or white (NI-W) LEDs at a significantly reduced intensity of 10 μmol·m-2 ·s-1 PPF (only 5.5% of the intensity of the main light source). Plant height was greatest under NI-Fr. The percent flowering was not affected by light quality during NI, and all plants flowered under all treatments. Among NI treatments, days to visible flower buds (DVB) increased under NI-Fr. All photoreceptor genes except phyB and FTL were highly expressed under normal LD conditions. Under the NI treatment with different qualities of light, these photoreceptor genes were expressed at even higher levels, except under NI-B, as compared to SD. These results suggest that morphogenesis, flowering, and the expression of transcription factor genes are affected by light quality during NI. Light quality during NI in the DNP geranium has more pronounced effects on morphogenesis than on flowering.

Slight vapor deficit accelerates graft union healing of tomato plug seedling

The application of grafting in tomato production has substantially improved tomato quality and yields. It has been demonstrated that humidity plays an important role in the graft healing of seedlings. This study focuses on the optimum relative humidity (RH) conditions for scion and rootstock healing of grafted tomato (Solanum lycopersicum L.) seedlings. Two tomato cultivars, ‘Super Sunload’ and ‘Super Dotaerang’, grafted onto ‘B-Blocking’ rootstock were subjected to one of three RH regimens: 70–80, 80–90, or 90–100%. The results showed that the scions of both cultivars showed apparent wilting under the 70–80 and 80–90% RH treatments. On this basis, the 90–100% RH treatment was subdivided into 95–96, 97–98, and 99–100% RH treatments, which were then applied. Among these subdivided RH treatments, the fresh weights of the scions and rootstocks significantly increased in response to the treatments of 97–98 and 99–100% RH, and the graft union connection of both cultivars was also enhanced after two days of healing. Furthermore, lower levels of endogenous H2O2 and less activity of antioxidant enzymes were observed in both cultivars in response to treatment with 95–96 or 97–98% RH, which indicated that less oxidative stress occurred. Overall, it is suggested that 97–98% is the optimal RH level for the graft healing of tomato seedlings.

Foliar applications of urea and a potent growth regulator ameliorate calyx-end cracking in persimmon.

Department of Horticulture, College of Agriculture and Life Sciences, Gyeongsang National University, Jinju 52828, Korea Institute of Agriculture and Life Science, Gyeongsang National University, Jinju 52828, Korea Pear Research Institute, National Institute of Horticultural and Herbal Science, Rural Development Administration, Naju 58216, Korea Central Instrument Facility, Gyeongsang National University, Jinju 52828, Korea Department of Biology Education, College of Education, Gyeongsang National University, Jinju 52828, Korea