The phenylurea cytokinin 4PU-30 protects maize plants against glyphosate action

The effects of the phenylurea cytokinin 4PU-30 and the herbicide glyphosate, applied alone and in combination on young maize plants were investigated. The influence of the compounds on the changes of growth, chlorophyll content, levels of hydrogen peroxide, and some stress markers, the activities of peroxidase, catalase, and glutathione-S-transferase, as well as glutathione amount were measured 3, 6, and 10 days after the treatment. The application of glyphosate increased the levels of lipid peroxidation, glutathione, and free proline content, ion fluxes, and the activity of catalase, guaiacol peroxidase, and glutathione-S-transferase, i.e., along with the inhibition of its target enzyme the herbicide induced also an oxidative stress. We found that the phenylurea cytokinin 4PU-30 alleviated in some extent the detrimental effects due to the glyphosate action. Moreover, we speculated that the cytokinin renders its protective action by induction of “hardiness” in the antioxidant defense systems in maize plants similarly to the effects observed after the application of some herbicide safeners.     

PLBs induction and clonal plantlet regeneration from leaf segment of commercial hybrids of Phalaenopsis

Induction of Protocorm-like bodies (PLBs) from leaf segments is a clonally propagation technology that used somatic embryogenesis regeneration from in vitro buds of floral stalks, and is a potential alternative for replacement actual low-yield and high-cost clonal propagation of Phalaenopsis orchids. The objective of this work was to evaluate induction of PLBs in leaf segments of two commercial hybrids of Phalaenopsis, arranged in culture media with different combinations of plant growth regulators. The leaf segments (0.4–0.5 cm²) used for PLBs inductions were obtained from young in vitro-induced shoots from inflorescence stalks. They are cultivated in NDM culture media, supplemented with combinations of plant growth regulators Naphthaleneacetic Acid, Thidiazuron and Benzyladenine. The flasks were kept for 60-d in darkness and then for cold white light with photon flux density of 35–40 μmol m^?2 s^?1. The cultivar ‘Ph908’ showed a higher percentage of leaf segments with PLBs (45%) and number of PLBs (25 per leaf segment), in medium containing 0.25 mg L^?1 of TDZ, whereas ‘RP3’ showed only 10% containing PLBs and 2 PLBs per leaf segment in NDM with 1.0 mg L^?1 NAA, 20 mg L^?1 BA and 0.125 mg L^?1 TDZ.     

Controlled atmosphere storage at high CO2 and low O2 levels affects stomatal conductance and influence root formation in kalanchoe cuttings

Since the response of cuttings to raised CO₂ concentration is not documented, controlled atmosphere (CA) storage of kalanchoe cuttings at combinations of high carbon dioxide and low oxygen levels was investigated to study the feasibility of using CA to sustain quality of cuttings prior to planting. During storage, stomata opening and plant fresh weight (FW) were measured, and root formation (RF) was recorded post storage. Storage atmosphere composition (10/2, 15/2, or 15/5; kPa CO₂/kPa O₂), storage duration (9 or 19 days), and cutting type (rooted or un-rooted) affected stomata conductance (G_s), and influenced FW and subsequent RF in cuttings of kalanchoe ‘Yellow Josefine’. In CA stored plants, G_s was high, 60–160 mmol m⁻² s⁻¹, indicating open stomata, whereas in control plants G_s was low, 5–14 mmol m⁻² s⁻¹, indicating closed stomata. Generally G_s values were higher for un-rooted than for rooted cuttings. Overall, cutting FW was reduced by CA storage with no significant differences in FW reduction between the CA treatments. RF of un-rooted CA stored cuttings was comparable to that of controls, whereas for rooted cuttings controls grew better than CA stored cuttings. CA at 10 kPa CO₂ and 2 kPa O₂ for 2–3 weeks could sustain un-rooted cuttings, in a pests-free state whilst retaining the ability of the cuttings RF. The results showed that stomata aperture may be altered by high CO₂ concentration combined with low O₂, and results indicated that this effect was not only caused by high CO₂ but also by low O₂ concentration. In addition, the results indicated that CA storage, stomata conductance, and water stress of kalanchoe cuttings may be correlated. Monitoring G_s of leaves of cuttings could be used as a non-destructive indicator of storability and quality status. Based on the novel positive preliminary results reported here, a protocol that focuses on minimising water loss should be developed and optimised for kalanchoe.     

Floral induction (FI) in longan (Dimocarpus longan, Lour.) trees: Part I. Low temperature and potassium chlorate effects on FI and hormonal changes exerted in terminal buds and sub-apical tissue

Floral induction (FI) in longan (Dimocarpus longan, Lour.) trees was achieved in controlled greenhouse experiments by low temperature (LT) and by the application of potassium chlorate at high temperature (HT + KClO₃) during two consecutive seasons. The latter treatment was successful also at temperatures above 20 °C. The present experiment was conducted to investigate possible alterations in the concentrations of plant hormones exerted by these two methods and to relate them to the floral induction process. The following hormones were examined by radioimmunoassay in the shoot apical buds (SAB), and in sub-apical bark and wood: the auxin indole-3-acetic acid (IAA); gibberellins (GAs); and the cytokinins zeatin/zeatin riboside (Z/ZR) and isopentenyl-adenine/isopentenyl-adenosine (iP/iPA).     

Micropropagation of Indica rice through proliferation of axillary shoots

Summary Week old seedlings of indica rice variety Jaya obtained on basal MS medium and further sub-cultured on agar solidified MS medium supplemented with cytokinins, sucrose (3% w/v) and mannitol (1% w/v) lead to development of multiple shoot buds. Shoot cultures were maintained and multiplied in liquid medium containing BAP 5 mg l^-1, sucrose (3% w/v) and mannitol (1% w/v). Profuse rooting was obtained on transfer to MS liquid medium containing IBA 1 mg l^-1 and sucrose (3% w/v). Complete plants were successfully transferred to soil and grown to maturity.     

多效唑对大豆根瘤、伤流及内源细胞分裂素类的影响

通过大豆栽培小区对比试验证明:多效唑对大豆根系的单株根瘤数、单株根瘤鲜重、单个根瘤鲜重、有效根瘤率均有明显增加,有利于提高根系活力和根瘤固氮能力。多效唑还促使伤流量增加并使伤流液中细胞分裂素类物质的效价明显提高。因此,根系合成的细胞分裂素类物质向上转运,可产生抗顶端优势,促进侧芽发育和器官分化,加强营养调运,延迟叶片衰老,增花增荚等生理效应,从而使大豆植株分枝增多,花荚、籽粒增加,叶片生育期延长,籽粒增重,产量提高。