Role of sucrose synthase and invertases during petal senescence in rose (Rosa hybrida L.)

Summary

The roles of sucrose synthase and invertases were explored in relation to petal senescence in rose (Rosa hybrida L.). A developmental shift in the activities of these enzymes was observed. Higher sucrose synthase activity (0.52 – 0.95 µmol sucrose min^–1 mg^–1 protein) was observed during the initial stages (S1 and S2) of flower bud development, in contrast to invertases. However, the lower activity (0.56 µmol sucrose min^–1 mg^–1 protein) of sucrose synthase at a later stage (S6) of senescence could help the mobilisation of vacuolar sucrose. The different isoforms of invertase exhibited variable levels of activity. Insoluble acid invertases (IAI) were the most active (11.01 µmol glucose min^–1 mg^–1 protein), followed by soluble acid invertases (SAI; 8.02 µmol glucose min^–1 mg^–1 protein), and soluble neutral invertases (SNI; 0.74 µmol glucose min^–1 mg^–1 protein) at Stage-4. A significant decline in invertase activities (IAI, 0.98; SAI, 1.25; SNI, 0.32 µmol glucose min^–1 mg^–1 protein) coincided with higher levels of ethylene production at the later stages (S5 and S6) of flower bud development and senescence. We propose that developmental as well as ethylene-mediated pathways account for petal senescence in rose.     

Sensitivity of the mitotic cells of barley (Hordeum vulgare L.) to insecticides on various stages of cell cycle

In this study, the genotoxic effects of insecticides in different phases of cell cycle were investigated in the mitotic cells of barley (Hordeum vulgare L.). The seeds of H. vulgare L. Var. Karan 4 were treated with different concentrations (0.05%, 0.1% and 0.5%) of insecticides alphamethrin (AM) and monocrotophos (MP) for 6 h after synchronization of cells in G₁, S and G₂ phase of cell cycle with the help of various presoaking durations (7 h, 17 h and 27 h.). Positive and negative control was run parallel in the form of ethyl methane sulphonate (EMS) and distilled water, respectively. The data indicate that higher dose of alphamethrin and monocrotophos produce toxicity, chromosomal aberrations and mitotic aberrations in Hordeum vulgare L. The present study indicates the genotoxic potential of the insecticides AM and MP and it also showed that S-phase of cell cycle was more sensitive compared to the G₁ and G₂ phases.     

水分胁迫下外源ABA对甘蔗叶绿素荧光特性的影响（英文）

以抗旱甘蔗品种ROC 22与不抗旱品种ROC 16为材料,研究水分胁迫条件下外源ABA对2个甘蔗品种叶片叶绿素含量及叶绿素荧光特性的影响。结果表明,水分胁迫下,ROC 16的叶绿素降解程度高于ROC 22,而外源ABA能够缓解这种降解作用;随着水分胁迫的加剧,两个甘蔗品种叶片的基础荧光（Fo）显著升高,PSⅡ原初光能转化效率（Fv/Fm）和PSⅡ的潜在活性（Fv/Fo）显著下降,光适应下PSⅡ最大光化学效率（Fv’/Fm’）、PSⅡ实际光化学效率（ΦPS2）、光化学猝灭系数（qP）显著下降,表明水分胁迫使甘蔗叶片PSⅡ反应中心受到伤害,施加外源ABA能部分减轻这种伤害,以对ROC 22作用尤为显著。     

Cytogenetic effects of commercially formulated atrazine on the somatic cells of Allium cepa and Vicia faba

In the present study cytogenetic effects of atrazine herbicide, were examined on the root meristem cells of Allium cepa and Vicia faba. Test concentrations were chosen by calculating EC₅₀ values of formulated atrazine against both the test systems which determined to be 30 mg l⁻¹ for A. cepa and 35 mg l⁻¹ for V. faba, respectively. For cytogenetic effects root meristem cells of A. cepa were exposed to 15, 30 or 60 mg l⁻¹ whereas V. faba to 17.5, 35 or 70 mg l⁻¹ for 4 or 24 h. Roots exposed for 4 or 24 h, after sampling, were left in water for 24 h recovery and sampled at 24 h post-exposure. A set of onion bulbs or seedlings of V. faba exposed to DMSO (0.3%) was run parallel for negative control. Treatment of atrazine significantly and dose-dependently inhibited the mitotic index (MI) and induced micronucleus formation (MN) chromosome aberrations (CA) and mitotic aberrations (MA) in both the test systems at 4 or 24 h. Root meristem cells examined at 24 h post-exposure also revealed significant (p < 0.001) frequencies of MN, CA or MA despite considerable decline. Chromosome breaks and fragments were found to be major CA whereas C-metaphase, chromosome bridges and laggards were prevalent MA. Results of our study, indicate that atrazine may produce genotoxic effects in plants. Further, both the plant bioassays found to be sensitive indicators for the genotoxicity assessment as the outcome of majority of in vivo/in vitro mammalian tests are comparable.     

Assessment of Heavy Metals in Spinach (Spinacia oleracea L.) Grown in Sewage Sludge–Amended Soil

The assessment of heavy metals in spinach (Spinacia oleracea) grown in sewage sludge–amended soil was investigated. The results revealed that sewage sludge significantly (P < 0.01) increased the nutrients and heavy metals such as cadmium (Cd), chromium (Cr), copper (Cu), manganese (Mn), and zinc (Zn) in the soil. The contents of metals were found to be below the maximum levels permitted for soils in India. The most agronomic performance and biochemical components of S. oleracea were found at 50% concentrations of sewage sludge in both seasons. The contents of Cd, Cr, Cu, Mn, and Zn in S. oleracea were increased from 5% to 100% concentrations of sewage sludge in both seasons. The order of contamination factor (Cf) of different heavy metals was Mn > Cd > Cr > Zn > Cu for soil and Cr > Cd > Mn > Zn > Cu for S. oleracea plants after application of sewage sludge. Therefore, use of sewage sludge increased concentrations of heavy metals in soil and S. oleracea.     

Crop Residue Retention and Nutrient Management Practices on Stratification of Phosphorus and Soil Organic Carbon in the Soybean–Wheat System in Vertisols of Central India

The long-term crop residue retention coupled with external nutrient inputs are crucial for maintaining soil phosphorus (P) and soil organic carbon (SOC) in Vertisols of Central India. A study was conducted to evaluate the long-term effect of three wheat residue management practices (residue burning, incorporation, and surface retention) in combination with three supplementary nutrient inputs (SNI) [control, fertilizer, and farmyard manure (FYM)] on stratification of P and SOC in the soybean–wheat system in Vertisol. The wheat residue either incorporated or retained on the soil surface increased the availability of P and SOC content as compared to the common practices of residue burning. Residue retention or incorporation increased stratification of P and soil organic carbon over the residue burning. Irrespective of the nutrient treatments, greater stratification ratio of SOC and P were registered under wheat residue incorporation or retention compared to residue burning. It is evident from the study that wheat residue incorporation or retention plus addition of FYM could be an effective strategy for increasing the soil fertility in a soybean–wheat system of Vertisols of Central India.     

Association of Pedilanthus leaf curl virus with yellow mottling and leaf curl symptoms in two jasmine species grown in India

Association of Pedilanthus leaf curl virus (PeLCV) with yellow mottling of crape jasmine (Tabernaemontana coronaria) and leaf curl of night blooming jasmine (Cestrum nocturnum) was investigated using a sequence analysis of the cloned full-length genome amplified by Rolling circle amplification using Φ-29 DNA polymerase. In the sequence analysis, virus isolates from T. coronaria (JN807764) and C. nocturnum (JQ012790) shared 95 % sequence identity with each other and the highest identity (93 %) and the closest phylogenetic relationships with PeLCV (AM712436); therefore, the virus isolates were identified as PeLCV strains. This report from India is the first on the occurrence of PeLCV on T. coronaria and C. nocturnum anywhere in the world.     

Assessment of surface and sub-surface waterlogged areas in irrigation command areas of Bihar state using remote sensing and GIS

Satellite remote sensing coupled with Geographical Information Systems (GIS) offers an excellent alternative to conventional mapping techniques in monitoring and mapping of surface and sub-surface waterlogged areas. In the present study, pre-monsoon and post-monsoon surface waterlogged areas were delineated in all the 132 irrigation command areas of the Bihar State, India using Indian Remote Sensing (IRS-1D) Linear Imaging Self Scanning Sensor (LISS-III) data acquired during the period 2002–2003. Normalized Difference Water Index (NDWI) was used primarily to delineate surface waterlogged areas. Perennial waterlogged and seasonal waterlogged areas were identified for the study area by integrating the waterlogged areas derived for both the pre- and post-monsoon seasons under GIS environment. Results show that the total surface waterlogged area in Bihar is 628 × 10³ ha, which is 10.57% of command area (5939 × 10³ ha) and spread over 132 command areas. Perennial surface inundation covers 2.95% of the waterlogged area in all the command areas. Maximum waterlogged area is observed in Gandak command (212 × 10³ ha) followed by Eastern Kosi irrigation scheme (116 × 10³ ha) and Sone modernization scheme (82 × 10³ ha), respectively. Further, waterlogged areas induced by rise in groundwater level were also assessed spatially under GIS environment using the ground water level data pertaining to pre- and post-monsoon seasons of the year 2002–2003 which were spread all over the study area. The analysis of pre- and post-monsoon groundwater levels indicates that the area under non-critical category during pre-monsoon period was reduced from 4287 × 10³ ha (72.72% of command) to 1391 × 10³ ha (23.42%) in the post-monsoon. Area under most critical category during post-monsoon period increased from 0.083 × 10³ ha of command area in pre-monsoon period to 50 × 10³ ha. The study demonstrates utility of integration of remote sensing and GIS techniques for assessment of waterlogged areas particularly in regions where waterlogging conditions occur both due to excessive irrigation and accumulation of rain and floodwaters.