Search Results (11)

Macadamia (Macadamia integrifolia), Macadamia tetraphylla and hybrids, a crop of high economic and nutritional importance, faces challenges with low fruit set rates and severe fruit drop. To address this, we investigated the effects of exogenous plant growth regulators (PGRs) and boron fertilizer on the development, fruit set, and yield of the A4 macadamia variety. The study was conducted in 2024 at the Lujiangba research base (China, Yunnan Province). Five treatments were applied during key growth stages: boron (B), brassinosteroids (BR), N-(2-Chloro-4-pyridyl)-N’-phenylurea (CPPU), 6-benzylaminopurine (6-BA), and gibberellic acid (GA₃). Growth stages include flower bud formation, peak flowering, and fruiting. Our findings revealed that B treatment significantly increased pollen viability (95.69% improvement) and raceme length (23.97% increase), while BR enhanced flower count per raceme (26.37% increase) and CPPU improved flower retention (10.53% increase). Additionally, GA₃ and 6-BA promoted leaf expansion in new shoots, increasing leaf length by 39.83% and 31.39%, respectively. Notably, B application significantly improved total yield (43.11% increase) and fruit number (39.12% increase), whereas BR maximized nut shell diameter (5.7% increase) and individual nut weight (19.9% increase). Furthermore, CPPU and 6-BA markedly improved initial fruit set rates, while GA₃, BR, and B effectively reduced early fruit drop. Physiological analyses indicated that elevated soluble sugars and proteins in flowers correlated with higher initial fruit set, whereas increased endogenous cytokinin and GA₃ levels improved fruit retention and reduced drop rates. Based on these findings, we propose an integrated approach to optimize productivity: applying 0.02% B at the floral bud stage, 2 mg/L 6-BA at full bloom, and a combination of 0.02% B and 0.2 mL/L BR during early fruit set. This strategy not only enhances yield but also mitigates fruit drop, offering practical solutions for macadamia production. Full article

Epigeal cotyledons with excised embryonic axes are often used as a model system to study the processes of cell division and expansion. These processes are regulated by diverse phytohormones and signaling molecules. Phytohormones modulate antioxidant defense systems and interact with reactive oxygen species (ROS) to synchronize normal plant cell growth. This study provides new information concerning alterations in enzymatic antioxidants linked to the production and scavenging of ROS in excised epigeal cotyledons of zucchini grown on solutions of methyl jasmonate (MeJA) and cytokinins (CKs)—N⁶-benzyl adenine and N₁-(2-chloropyridin-4-yl)-N₂-phenylurea—in the presence or absence of light under laboratory conditions. The cotyledon material was used to determine the dynamics of selected biochemical parameters starting from the 2nd to the 6th day of incubation. In general, our results revealed that exogenous MeJA caused a reduction in the content of hydrogen peroxide (H₂O₂) and free proline, as well as in the activity of superoxide dismutase (SOD), guaiacol peroxidase (POX) and catalase (CAT) in dark-grown cotyledons. Applied alone, both cytokinins increased most of the parameters studied, except proline and protein levels. However, when MeJA was combined with CKs, it acted in a diverse manner, ranging from antagonistic to synergistic depending on the cytokinin type, parameter measured and light regime. Similar alterations were also found in the levels of leaf pigments in the cotyledons grown under light conditions. In general, the changes in the antioxidant enzyme activities due to light were more intense than those observed in dark-grown cotyledons. The data obtained show, for the first time, the involvement of the hormonal interplay between MeJA and CKs on the biochemical changes in antioxidant defense during cotyledon growth under different light conditions. Full article

CPPU, N-(2-Chloro-4-pyridyl)-N-phenylurea, is a synthetic cytokinin extensively used to enhance fruit size and overall quality in several crops, including kiwifruit. This study aimed to investigate the effects of three different CPPU application strategies (2.3, 3.0, and 4.6 ppm) and two crop load levels on key fruit quality parameters at harvest, as well as on post-harvest storage performance. Our results demonstrate that two applications of CPPU (4.6 ppm) significantly increased fruit weight, especially under standard crop-load conditions, likely due to more efficient resource allocation. Additionally, fruit firmness improved with two or three CPPU applications, probably because of enhanced cell wall development. Crop load consistently influenced fruit firmness, with lower loads resulting in softer fruits. The soluble solids content was not significantly affected by the two CPPU applications; however, it was notably influenced by crop load, with fruits from the standard crop load showing higher sugar accumulation. A similar trend was observed in fruit dry weight, where CPPU had a greater impact under standard crop loads. Regarding post-harvest performance, CPPU applications showed a limited effect on maintaining fruit firmness during the first five months of storage. Overall, CPPU can be a potential strategy to enhance fruit quality, but its effectiveness depends heavily on field management practices. Therefore, controlling field variables is essential to fully realize the benefits of CPPU and to avoid interference with the plant’s physiological responses. Full article

Blossom end enlargement (BEE) is a postharvest deformation that may be related to the influx of photosynthetic assimilates before harvest. To elucidate the mechanism by which BEE occurs, expression marker genes that indicate the physiological condition of BEE-symptomatic fruit are necessary. First, we discovered that preharvest treatment with a synthetic cytokinin, N-(2-Chloro-4-pyridyl)-N’-phenylurea (CPPU), promoted fruit growth and suppressed BEE occurrence. This suggests that excessive assimilate influx is not a main cause of BEE occurrence. Subsequently, the expression levels of seven sugar-starvation marker genes, CsSEF1, AS, CsFDI1, CsPID, CsFUL1, CsETR1, and CsERF1B, were compared among symptomatic and asymptomatic fruits, combined with and without CPPU treatment. Only CsSEF1 showed a higher expression level in asymptomatic fruits than in symptomatic fruits, regardless of CPPU treatment. This was then tested using fruits stored via the modified-atmosphere packaging technique, which resulted in a lower occurrence of BEE, and the asymptomatic fruits showed a higher CsSEF1 expression level than symptomatic fruits, regardless of the packaging method. CsSEF1 codes a CCCH-type zinc finger protein, and an increase in the expression of CsSEF1 was correlated with a decrease in the fruit respiration rate. Thus, CsSEF1 may be usable as a BEE expression marker gene. Full article

Callus cultures of the Iranian medicinal plant Salvia atropatana were initiated from three-week-old seedlings on Murashige and Skoog (MS) medium supplemented with α-naphthaleneacetic acid (NAA) and various cytokinins. Although all tested hormonal variants of the medium and explant enabled callus induction, the most promising growth was noted for N-(2-chloro-4-pyridyl)-N′-phenylurea (CPPU)-induced calli. Three lines obtained on this medium (cotyledon line-CL, hypocotyl line—HL, and root line—RL) were preselected for further studies. Phenolic compounds in the callus tissues were identified using UPLC–MS (ultra-performance liquid chromatography–mass spectrometry) and quantified with HPLC (high-performance liquid chromatography). All lines exhibited intensive growth and contained twelve phenolic acid derivatives, with rosmarinic acid predominating. The cotyledon-derived callus line displayed the highest growth index values and polyphenol content; this was exposed to different light-emitting diodes (LED) for improving biomass accumulation and secondary metabolite yield. Under LED treatments, all callus lines exhibited enhanced RA and total phenolic content compared to fluorescent light, with the highest levels observed for white (48.5–50.2 mg/g dry weight) and blue (51.4–53.9 mg/g dry weight) LEDs. The selected callus demonstrated strong antioxidant potential in vitro based on the 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS), 2,2-diphenyl-1-picrylhydrazyl (DPPH), and ferric reducing antioxidant power (FRAP) tests. Our findings confirm that the S. atropatana callus system is suitable for enhanced rosmarinic acid production; the selected optimized culture provide high-quality plant-derived products. Full article

Abiotic stress is responsible for a significant reduction in crop plant productivity worldwide. Ultraviolet (UV) radiation is a natural component of sunlight and a permanent environmental stimulus. This study investigated the distinct responses of young wheat and einkorn plants to excessive UV-B radiation (180 min at λ_max 312 nm) following foliar pretreatment with 1 µM synthetic cytokinin 4PU-30. Results demonstrated that UV radiation significantly amplified hydrogen peroxide levels in both wheat and einkorn, with einkorn exhibiting a more pronounced increase compared to wheat. This elevation indicated the induction of oxidative stress by UV radiation in the two genotypes. Intensified antioxidant enzyme activities and the increased accumulation of typical stress markers and non-enzyme protectants were evidenced. Transcriptional activity of genes encoding the key antioxidant enzymes POX, GST, CAT, and SOD was also investigated to shed some light on their genetic regulation in both wheat and einkorn seedlings. Our results suggested a role for POX1 and POX7 genes in the UV-B tolerance of the two wheat species as well as a cytokinin-stimulated UV-B stress response in einkorn involving the upregulation of the tau subfamily gene GSTU6. Based on all our findings, it could be concluded that 4PU-30 had the potential of alleviating oxidative stress by attenuating the symptoms of superfluous UV-B illumination in the two examined plant species. Full article

Natural and synthetic phytohormones are widely used in agriculture. The synthetic cytokinin ethylenediurea (EDU) induces protection in plants against ozone phytotoxicity. In our study, new hybrid derivatives of EDU were synthesized and tested for phytoactivity. The germination potential (Gp), germination of seeds (G), and relative water content in leaves (RWC), characterizing the drought resistance of plants, were determined. The results of laboratory studies showed that EDU and its hybrid derivatives have a positive effect on root length, the growth and development of shoots, as well as the ability of plants to tolerate stress caused by a lack of water. Full article

The application of the plant growth regulator 1-(2-chloro-4-pyridyl)-3-phenylurea (CPPU) is extensively used for red-fleshed kiwifruits or ‘Donghong’, but it has toxicological properties. Extra plant growth regulators (PGRs) were screened for partial substitution of CPPU (10 mg L⁻¹) to the crops to minimize the CPPU content. The results showed that CPPU at a concentration of 5 mg L⁻¹ plus 14-hydroxylated brassinosteroid (14-OH BR) at a concentration of 0.15 mg L⁻¹ has a nearly equal effect to CPPU at a concentration of 10 mg L⁻¹; it maintains the kiwifruit yields and quality as well as increases the postharvest time. Transcriptome sequencing data revealed that the regulation of 14-OH BR on kiwifruit growth acts mainly by activating Brassinosteroid (BR) signaling to synergistically and antagonistically stimulate the signaling of other endogenous growth regulators, including auxin (IAA), abscisic acid (ABA), cytokinin (CK), gibberellin (GA), jasmonic acid (JA) and ethylene (ET). Full article

Castanea henryi is a monoecious plant with a low female-to-male ratio, which limits its yield. The phytohormone cytokinin (CK) plays a crucial role in flower development, especially gynoecium development. Here, the feminizing effect of CK on the development of C. henryi was confirmed by the exogenous spraying of N-(2-chloro-4-pyridyl)-N’-phenylurea (CPPU). Spraying CPPU at 125 mg·L⁻¹ thrice changed the male catkin into a pure female catkin, whereas at 5 mg·L⁻¹ and 25 mg·L⁻¹, only a part of the male catkin was transformed into a female catkin. A comparative transcriptome analysis of male catkins subjected to CPPU was performed to study the mechanism of the role of CKs in sex differentiation. Using Pearson’s correlation analysis between hormone content and hormone synthesis gene expression, four key genes, LOG1, LOG3, LOG7 and KO, were identified in the CK and GA synthesis pathways. Moreover, a hub gene in the crosstalk between JA and the other hormone signaling pathways, MYC2, was identified, and 15 flowering-related genes were significantly differentially expressed after CPPU treatment. These results suggest that CK interacts with other phytohormones to determine the sex of C. henryi, and CK may directly target floral organ recognition genes to control flower sex. Full article

The demand for virus-free hop planting material has increased in the last few years due to its multipurpose uses. The present study aimed to establish an effective protocol for clonal propagation of cv. Cascade using only the cytokinins as PGRs in all stages of micropropagation: (i) in vitro culture initiation using single-node micro-cuttings inoculated on modified Murashige and Skoog (MSm) medium solidified with Plant agar and supplemented with 0.5 mg L⁻¹ 6-benziyladenine (BA) with 76% recorded viability of nodal explants; (ii) in vitro multiplication of multinodal shoots on MSm medium gelled with Plant agar and supplemented with different types and concentrations of cytokinins: 2 mg L⁻¹ kinetin (KIN), 0.7 mg L⁻¹ 1-(2-Chloro-4-pyridyl)-3-phenylurea) (1 CPPU), 2 mg L⁻¹ meta-topoline (mT) and 0.5 mg L⁻¹ BA, which was the best variant for shoot proliferation (9.48 ± 0.78 shoots/explant); (iii) rooting and acclimatization with the best results obtained by ex vitro rooting and acclimatization of plants in the same stage in perlite (96.00 ± 0.60% acclimatized rooted plants with 100% survival under greenhouse conditions). The true-to-type nature of in vitro raised plants with the mother plant was assessed by Random Amplified Polymorphic DNA (RAPD) and Start Codon Target Polymorphism (SCoT) molecular markers, and then their genetic uniformity were confirmed. Full article

N1-(2-chloro-4-pyridyl)-N3-phenylurea (CPPU), a synthetic cytokinin-active compound, is widely applied to induce parthenocarpic fruit set and enhance melon fruit enlargement (Cucumis melo L.). CPPU may also influence fruit quality; however, the mechanisms through which this occurs remain unknown. We investigated the differences in volatile emissions between parthenocarpic fruit set by CPPU (C) and seeded fruit set by artificial pollination (P). Gas chromatography–mass spectrometry (GC–MS) analysis revealed that six volatile organic compounds (VOCs) emitted by the P-group fruits were not detected in C-group fruits. The relative abundances of another 14 VOCs emitted by the CPPU-treated fruits were less than those in the P-group fruits. RNA sequencing analysis indicated that a total of 1027, 994, and 743 differentially expressed genes (DEGs) were detected in the C20 (treatment with 20 mg·L^–1 CPPU) vs. P, P-C20 (pollination followed by 20 mg·L⁻¹ CPPU treatment) vs. P, and P-C20 vs. C20 treatments, respectively. Compared with the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases, the DEGs related to fatty acid degradation and metabolism, which contribute to volatile production, were enriched. In particular, DEGs such as carotenoid cleavage dioxygenase (CCD)-, lipoxygenase (LOX)-, alcohol dehydrogenase (ADH)-, and alcohol acyltransferase (ATT)-related genes were closely related to the formation of volatiles. In summary, our study provides a metabolic and transcriptomic atlas, reveals the impact of CPPU on VOCs, and enhances our understanding of the mechanisms of CPPU that contribute towards generally reducing the quality of melon fruit. Full article