Distribution of 14CO2 during ontogeny of chickpea (Cicer arietinum) grown at two moisture levels

The distribution of assimilates of ¹⁴CO₂ in ethanol soluble and insoluble fractions was measured at 20-day intervals from 45–135 days after sowing (DAS) in chickpea (Cicer arietinum) grown at two moisture levels. The contribution of pre-flowering assimilates to pods, although very low, was higher under the stress conditions. At the time of harvest, the recovery of ¹⁴C in pods was 0.4 and 0.9% of the total ¹⁴C fed 45 DAS in soluble and 2.5 and 5.1% in insoluble fractions in control and stressed plants, respectively. The %¹⁴C received by nodules continuously decreased with increasing age of plants. Stressed plants diverted more ¹⁴C to nodules, compared to control, during vegetative and flowering stages. During active seed filling, stressed plants diverted more ¹⁴C to reproductive parts and less to nodules, compared to control. Significant amounts of ¹⁴C were retgined by the stem and leaves during the seed-filling period and it appears that there is scope for the remobilisation of pre-flowering, as well as post-flowering assimilates for seed-filling of chickpea.     

HISTORY OF ARIDLAND VEGETATION AND CLIMATE: A GLOBAL PERSPECTIVE

1. The origin and history of aridlands and their vegetational cover is closely related to geological history, especially in relation to plate tectonics, mountain building, land-and sea-level changes and ice ages, and the arrival of modern humans and their subsequent development. 2. A close relationship exists between world temperatures and precipitation. Therefore, the development of present-day zonal, aridland vegetation and climate cannot be divorced from the history of the latest ice age. 3. The combined geological and palaeobotanical evidence demonstrate that whilst the origin of modern openland and aridland vegetation went back to the time of the origin of angiosperms during the Cretaceous, its subsequent expansion went hand in hand with the lowering of world temperatures during the Palaeogene and Neogene, when a series of angiospermous families having dominantly herbaceous and openland taxa, as members, appeared successively in the stratigraphic record. 4. The successive lowering of world temperatures had the overall effect of reducing precipitation levels all over the globe. Consequently, high rainfall areas, bearing closed forests, became progressively smaller and smaller and the decreased rainfall promoted the evolution and expansion of low biomass, openland and aridland vegetation. 5. The break-up of regional closed forests had started from the middle Miocene but the main expansion of zonal, aridland vegetation, in low and middle latitudes, appears to have taken place, together with the expansion of tundra vegetation, at high latitudes, from the late Pliocene. Glaciations of a magnitude of at least two-thirds that of the late Pleistocene glacial maxima started to occur about that time, 25 Ma ago. 6. The alternations between cold, glacial and warm, interglacial periods, during the late Neogene, especially with increased amplitude during the last 0.4 Ma, allowed less and less time for forest vegetation to expand and stabilize during the warm intervals, with the result that openland and aridland vegetation was able to expand to unprecedented levels. 7. Further, as man increased fire frequencies during the late Pleistocene, the relatively fire-sensitive and mesophytic taxa were selectively eliminated and more and more forests were opened to invasion by openland taxa in low and middle latitudes. Later on, with the clearance of forests for agriculture, the overall effect on vegetation was to create open landscapes which favoured the expansion of openland taxa at low, middle and high latitudes, during an interglacial, that is, the Holocene, a feature that is unprecedented in the entire earlier geological record.     

Relative Sensitivity and Tolerance of some Gladiolus Cultivars to Sulphur Dioxide

Five Gladiolus cultivars, namely ‘Aldebaran’, ‘BrightEye’, ‘Illusion’, ‘Manisha’ and‘Manmohan’, were exposed to 1 and 2 µg l^–1sulphur dioxide to test their relative-sensitivity toleranceto the pollutant Plants were fumigated experimentally for 2h daily Foliar injury symptoms were observed first in ‘Manisha’followed by ‘Aldebaran’ and ‘Illusion’at the higher dose Photosynthetic pigments and leaf extractpH were significantly decreased, particularly in ‘Manisha’and ‘Illusion’ Overall disturbances in the plantmetabolism due to SO₂ treatment led to retarded growth of plants,as evident from decreased shoot length and phytomass valuesThe order of sensitivity of the five Gladiolus cultivars toSO₂ was as follows, with the greatest first Manisha, Illusion,Aldebaran, Bright Eye, Manmohan Cultivars, Gladiolus, sensitivity, sulphur dioxide, tolerance     

Effect of Applied Nitrogen on N2 Fixation, Assimilation of Nitrate and Ammonia in Nodules of Field-grown Moong (Vigna radiata)

A field experiment was conducted to study the effect of nitrogenapplication at 15, 30 and 45 kg ha^–1 of urea at pre-flowering(PF) and pod initiation (PI) stages on the activity of nitrogenase(N₂ase), nitrate reductase (NR) and other related parametersin the nodules of moong (Vigna radiata). Nitrogen applied atPF or PI stage was found to be inhibitory to N₂ase and glutaminesynthetase (GS) activities except at 15 kg N ha^–1 whenapplied at PF in the case of N₂ase. At both the stages therewas increase in NR and glutamate dehydrogenase (GDH) activitieswith the application of nitrogen. Seed yield increased by 18per cent with the application of 15 kg N ha^–1 at PI stagewhereas nitrogen application at PF stage only increased strawyield significantly. Nitrate reductase, nitrogenase, nitrogen application, ammonia assimilation, Vigna radiata     

Biology of Bactrocera (Zeugodacus) tau (Walker) (Diptera: Tephritidae)

The biology of the fruit fly Bactrocera tau, an important horticultural pest, was studied under laboratory conditions at 25°C and 60–70% relative humidity on Cucurbita maxima. The duration of mating averaged 408.03 ± 235.93 min. After mating, the female fly had a preoviposition period of 11.7 ± 4.49 days. The oviposition rate was 9.9 ± 8.50 eggs and fecundity was 464.6 ± 67.98 eggs/female. Eggs were elliptical, smooth and shiny white, turning darker as hatching approached, and measured 1.30 ± 0.07 mm × 0.24 ± 0.04 mm. The chorion has polygonal microsculpturing and is species-specific with polygonal walls. The egg period lasts for 1.3 ± 0.41 days. The duration of the larval period is 1.2 ± 0.42, 1.7 ± 0.48 and 4.0 ± 0.94 days for first, second and third instars, respectively. Pupation occurs in the sand or soil and pupal periods are 7.0 ± 0.47 days. The life cycle from egg to adult was completed in 14.2 ± 1.69 days; the longevity of mated females and males was 130.33 ± 14.18 and 104.66 ± 31.21 days, respectively. At least two to three generations were observed from June 2008 to June 2009.     

Evidence for a role for L-proline as a salinity protectant in the cyanobacterium Nostoc muscorum

Nostoc muscorum required an active proline oxidase in order to assimilate exogenous proline as a source of fixed nitrogen. A mutant strain (Ac^r) resistant to growth inhibition by L-azetidine-2-carboxylate (AC) was found to be deficient in proline oxidase activity, and to be a proline overaccumulator. Proline overaccumulation, resulting either from mutational acquisition of the Ac^r phenotype or from salinity-inducible uptake of exogenous proline, conferred enhanced salinity tolerance in this cyanobacterium.