Changes in Respiratory Potential of Dormant and Non-dormant Galium aparine L. (cleavers) Seeds during Dry Storage

Hilton, J. R. and Thomas, J. A. 1987. Changes in respiratorypotential of dormant and non-dormant Galium aparine L. (cleavers)seeds during dry storage.—J. exp. Bot. 38: 1484–1490. Pre-germinative rates of O₂ uptake of two collections of Galiumaparine L. seed were compared throughout a 9 month period ofdry storage at 4 °C, 23 °C and at ambient (frost-protected)temperatures. Uptake of O₂ by the dormant seeds was generallyhigher than that of the less dormant seeds except when freshly-harvested.Moreover, changes in the O₂ consumption of seeds stored at ambienttemperatures could be associated with periods of germinationand seedling emergence in the field. The results are discussedin relation to changes in respiratory metabolism during dormancybreakage.     

The BULT Melanoma: A Spontaneous Transplantable Tumor in Mice

The BULT melanoma originated at Brown University as a spontaneous, small black nodule on the tail of an adult female mouse of the LT/Ch strain. Histological examination of a portion of the tumor indicated that it was intradermal and consisted predominantly of heavily melanized, ovoid to fusiform cells with melanin-laden macrophages scattered among them. The BULT melanoma has been maintained in LT/Ch mice for approximately 5 years by periodic transplantation, at first subcutaneously on the flanks and, more recently, intramuscularly in the hind legs. The shift in transplantation site was made following a marked decline in the growth of subcutaneous grafts. The transplants have retained the uniform deep-black melanization and general histology of the primary melanoma. Numerous melanosomes at all stages of development are found within the melanoma cells. DOPA-positive cytoplasmic vesicles are abundant. Occasional autophagic vacuoles containing clusters of melanosomes are also present. A few metastases from the transplanted melanoma have been observed in lymph nodes and on one occasion in the lungs. When grown in vitro, BULT melanoma cells do not require special growth promoting agents (e.g., TPA; cAMP) in order to proliferate. The BULT melanoma differs in one or more respects from each of the other three transplantable spontaneous mouse melanomas widely used in cancer research. In addition, it arose in a strain of mice characterized by the spontaneous death of melanocytes while the latter are engaged in synthesizing eumelanin within hair follicles. Karyotypic analysis of cultured cells showed a modal chromosome number of 68 with a range of 58–72 chromosomes.     

The long-distance migration of Nilaparvata lugens (Stål) (Delphacidae) in China: radar observations of mass return flight in the autumn

Abstract.

• 1 A case study is presented of the autumn migration of the brown planthopper, Nilaparvata lugens (Stål), in the area of Nanjing in the People's Republic of China. The study was made using a high frequency (8 mm wavelength) radar and a net suspended from a kytoon.
• 2 The observations confirmed that long-distance return migrations occur in China in mid and late September, with N.lugens being carried on the prevailing north-easterly wind towards the autumn infestation and overwintering areas of the species.
• 3 After mass take-off in the late afternoon or at dusk, the migrants flew for several hours during the evening, often in a dense layer which formed at heights between about 400 and 1000m above ground. These layers often had well-defined ceilings corresponding to an air temperature of about 16°C. The migration height was above the top of the surface temperature inversion, i.e. the migrants did not fly at the height of the warmest air.
• 4 The dense layer concentrations overflying the radar were backtracked to source areas up to 240 km away in the north-east of Jiangsu Province. Planthoppers observed emigrating from the Nanjing area would reach areas in south Anhui Province or north Jiangxi Province if they flew for 12 h.
• 5 There was a second period of mass take-off at dawn. Insect layers sometimes formed but did not last longer than 1–2h.
• 6 The present results were strikingly different from those previously observed in the dry season in the Philippines, where migratory flight durations were largely confined to periods of about 30min at dusk and dawn.
• 7 Our observations are discussed in relation to the equator-wards return migrations undertaken in autumn by other insect species, and the importance of these migrations for the maintenance of long-flying genotypes in the overwintering populations is considered.

     

A comparison of the epidermis and pigment cells of the crocodile with those in two lizard species

Keratinization and pigmentation in Crocodilus niloticus skin were compared with the conditions in the lizards Lacerta viridis and Anolis carolinensis. The epidermis, both in the crocodile and in lizards, is arranged to form a surface pattern of scales and narrower intervening hinge regions. Similar keratin-bound substances were found in the crocodile and lizard stratum corneum. Nevertheless, the greater uniformity in histological structure and in distribution of chemical substances throughout the depth of the crocodile stratum corneum was in marked contrast to the lizards, which showed morphological differences, and differences in intensities of chemical reactions in the horny cells laid down early and late in each keratinization cycle. In the crocodile, keratin-bound S-S and SH are uniformly distributed in the horny scales, but in the lizards the superficial cells have most S-S and the lowermost keratinized cells most SH. The loosely arranged horny cells in the crocodile are shed in small flakes as in mammals, in contrast to lizards which undergo periodic sloughs of a compact stratum corneum. In the lizards, the intermediate layer between two horny layer generations contains no detectable S-S and is probably unkeratinized, so that when these cells die a fission zone is formed. The crocodile scales each contain a raised pigmented papule in which melanin is introduced into the epidermal cells, and keratinization is also different from the neighbouring area. Guanophores and lipophores are absent in the crocodile, although present in the lizards. All contain prominent dermal melanophores.     

The Response of Bean Plants to UV-B Radiation Under Different Irradiances of Background Visible Light

Plants of Phaseolus vulgaris L. (cv. Stella) were grown in controlledconditions under three different irradiances of visible lightwith or without UV-B (280–320nm) radiation. The biologicallyeffective UV-B radiation (UV-B_BE) was 6.17 kJ m^–2 d^–1,and simulated a c. 5% decrease in stratospheric ozone at 55.7?N,13.4?E. The photon flux densities of the photosyntheticallyactive radiation (PAR, 400–700 nm) were either 700 µmolm^–2–1 (HL), 500, µmol m^–2 s^–1(ML) or 230 µmol m^–2 s^–1 PAR (LL). Under highlight (HL) conditions plus UV-B radiation, bean plants appearedmost resistant to the enhanced levels of UV-B radiation, andresponded only by increasing leaf thickness by c. 18%. A smallincrease in UV screening pigments was also observed. Both thelower irradiances (ML and LL) increased the sensitivity of theplants to UV-B radiation. Changes in leaf structure were alsoobserved. Photosystem II was inhibited under ML and LL togetherwith UV-B radiation, as determined by Chi fluorescence inductionand calculation of the fluorescence half-rise times. Leaf reflectivitymeasurements showed that the amount of PAR able to penetrateleaves of UV-B treated plants was reduced, and that a possiblecorrelation may exist between the reduced PAR levels, loss ofChi and lowered photosynthetic activity, especially for LL +UV-Bgrown plants, where surface reflection from leaves was highest.Changes in leaf chlorophyll content were mostly confined toplants grown under LL + UV-B, where a decrease of c. 20% wasfound. With regard to protective pigments (the carotenoids andUV screening pigments) plants subjected to different visiblelight conditions responded differently. Among the growth parametersmeasured, there was a substantial decrease in leaf area, particularlyunder LL + UV-B (c. 47% relative to controls), where leaf dryweight was also reduced by c. 25%. Key words: Chlorophyll fluorescence induction, bean, flavonoids, Phaseolus vulgaris, reflectance, UV-B radiation     

Cell Cycle Activation During Imbibition and Visible Germination in Embryos and Megagametophytes of Jack Pine (Pinus banksiana Lamb.)

Flow cytometric determination of cell cycle activation duringimbibition and visible germination in five families of jackpine (Pinus banksiana Lamb.) embryos and megagametophytes revealedthat in seeds that had undergone no imbibition the majorityof cells were in the 2C state. As the imbibition period increased,less of the nuclei were blocked in the G0/G1 state and morebecome active in the cell cycle. The augmentation in the nucleiactive in the 2C–4C cycle as well as those with DNA levelshigher than the 4C state occured gradually and preceeded radicleemergence. In megagametophyte tissue examined at various stagesof imbibition, cell cycle activity became apparent rapidly followingimbibition. In nuclei of green and white embryos examined separatelythe ²frequency distributions were significantly different forall three families after 144h. As imbibition period increased,fewer nuclei from the green embryos were blocked in the 2C state,and more became active in the 2C–4C cell cycle. This wasnot the case for white embryos where no significant linear relationwas noted. Cell cycle activity in the hypocotyl+cotyledons regionand the emerging radicle were examined separately. Functionalrelations found in the hypocotyl+cotyledons region were notevident in the radicle. As visible germination proceeded, cellcycle activity in the hypocotyl + cotyledons region for thisperiod of germination showed a reversal of the activity notedduring imbibition: fewer nuclei were active and once again ahigher proportion were found in the 2C state. cell cycle; C levels; DNA content; flow cytometry; germination; imbibition; jack pine; megagametophyte; Pinus banksiana Lamb