Separating the effects of climate and vegetation on evapotranspiration along a successional chronosequence in the southeastern US

We combined Eddy‐covariance measurements with a linear perturbation analysis to isolate the relative contribution of physical and biological drivers on evapotranspiration (ET) in three ecosystems representing two end‐members and an intermediate stage of a successional gradient in the southeastern US (SE). The study ecosystems, an abandoned agricultural field [old field (OF)], an early successional planted pine forest (PP), and a late‐successional hardwood forest (HW), exhibited differential sensitivity to the wide range of climatic and hydrologic conditions encountered over the 4‐year measurement period, which included mild and severe droughts and an ice storm. ET and modeled transpiration differed by as much as 190 and 270 mm yr^?1, respectively, between years for a given ecosystem. Soil water supply, rather than atmospheric demand, was the principal external driver of interannual ET differences. ET at OF was sensitive to climatic variability, and results showed that decreased leaf area index (L) under mild and severe drought conditions reduced growing season (GS) ET (ET_GS) by ca. 80 mm compared with a year with normal precipitation. Under wet conditions, higher intrinsic stomatal conductance (g_s) increased ET_GS by 50 mm. ET at PP was generally larger than the other ecosystems and was highly sensitive to climate; a 50 mm decrease in ET_GS due to the loss of L from an ice storm equaled the increase in ET from high precipitation during a wet year. In contrast, ET at HW was relatively insensitive to climatic variability. Results suggest that recent management trends toward increasing the land‐cover area of PP‐type ecosystems in the SE may increase the sensitivity of ET to climatic variability.     

Premature Drying, Fluridone-Treatment, and Embryo Isolation During Development of Maize Kernels (Zea mays L.) Induce Germination, but the Protein Synthetic Responses are Different. Potential Regulation of Germination and Protein Synthesis by Abscisic Acid

Freshly harvested, developing kernels of maize (Zea mays L.)do not germinate up to 77 d after pollination, but can be inducedto do so by fluridone, premature desiccation, and isolationof the developing embryo. The pattern of protein synthesis indeveloping maize embryos is distinct from that during germinationand subsequent seedling growth. Premature desiccation at 35DAP elicits a pattern of protein synthesis upon rehydrationwhich is similar to that in germinated embryos from mature drykernels. Fluridone-induced viviparous germination is accompaniedby changes in the synthesis of some proteins to a post-germinativepattern, but some developmental proteins continue to be synthesized.Embryos isolated from developing kernels at 35 DAP germinatewhen incubated on water; they also produce some developmentalproteins during germination. Kernels from developing cobs at35 DAP which are detached from the mother plant and maintainedin an atmosphere of high relative humidity (moist controls)do not germinate, but neither do they continue a clearly definedpattern of either developmental or germinative protein synthesis.Drying is thus critical to effect a clear transition of proteinsynthesis from a developmental to a germinative mode in maizeembryos. Abscisic acid within the developing embryos is reduced by fluridone,but to a lesser extent by premature drying or maturation drying.Changes in sensitivity to abscisic acid by the developing embryomay be as, or more, important in permitting germination, andthe attendant synthesis of proteins, than changes in abscisicacid content. Key words: Maize (Zea mays L.), germination, vivipary, desiccation, abscisic acid     

Intracellular Localization and Sedimentation Coefficient of DNA Ligase in Oocytes of the Starfish, Asterina pectinifera

When immature oocytes of Asterina pectinifera were separated into karyoplasts (nuclear fragments) and cytoplasts (anuclear fragments) by cytochalasin B treatment and centrifugation in a sucrose gradient, almost all their DNA ligase activity was recovered in the karyoplasts. Thus, DNA ligase seems to be localized in the germinal vesicles or their vicinity in starfish oocytes. No ontogenic change in the activity of DNA ligase per oocyte, egg or embryo, or in its sedimentation coefficient (4.1 S) was observed during oocyte maturation, fertilization, or early development.     

Ovarian development and vitellogenesis in the sawfly,Athalia rosae ruficornis Jakovlev (Hymenoptera,Tenthredinidae)

Summary

Ovarian development in Athalia rosae ruficornis Jakovlev (Hymenoptera: Tenthredinidae) is described. Number of nurse cells per egg chamber is most often around 60 (close to 63 according to the 2ⁿ–1 rule), but in many cases it deviates from this number significantly. Two major yolk proteins [vitellins: large (apparent molecular weight 160–170 kD) and small (48–50 kD] were identified by SDS-PAGE. Western blotting and immunochemical detection using polyclonal antibodies prepared against each of the vitellins revealed that adult female but not male (both haploid and diploid) hemolymph contains vitellogenins corresponding to these vitellins. Vitellogenins become detectable in the hemolymph of late pupae, and vitellins one day later in the oocytes of adults. Transplantation of immature ovaries into the adult male abdomen caused not only significant accumulation of vitellins in the oocyte but also appearance of small amounts of hemolymph vitellogenins in host males. Injection of homogenate of immature ovaries also caused appearance of small amounts of hemolymph vitellogenins in host males.     

Japanese oak silkmoth feeding preference for and performance on upper-crown and lower-crown leaves

We quantified differences in leaf traits between upper and lower crowns of a deciduous oak, Quercus acutissima, and examined feeding preference, consumption and performance of the Japanese oak silkmoth, Antheraea yamamai, for those leaves. Upper‐crown leaves had significantly smaller area, larger dry mass per area, greater thickness, lower water content, higher nitrogen content and a higher N/C ratio than lower‐crown leaves. When simultaneously offered upper‐crown and lower‐crown leaves, moth larvae consumed a significantly larger amount of the former. However, when fed with either upper‐crown or lower‐crown leaves (no choice), they consumed a significantly larger amount of the latter. Female larvae reared on upper‐crown leaves had a significantly smaller fresh weight, but attained a significantly larger pupal fresh and dry weight, with a significantly higher relative growth rate than those on lower‐crown leaves. Although, like female larvae, male larvae had a significantly smaller fresh weight when reared on upper‐crown leaves, they had a significantly larger value only for pupal dry weight. These results suggest that: (i) larvae ingest a greater amount of lower‐crown leaves to compensate for the lower nitrogen content of the foliage, resulting in having an excess of water because of the higher water content of the foliage; (ii) feeding preference for upper‐crown leaves accords with better performance (with respect to dry pupal weight and relative growth rate) on the foliage; (iii) better performance is explained by a higher nitrogen content and N/C ratio of the upper‐crown foliage; and (iv) the effects of leaf quality on performance differ between sexes.     

Photoreception in decapitated larvae of silkworm Bombyx mori

To investigate the photoreception that controls daily oscillations at the periphery in insects, we decapitated larvae of the silkworm Bombyx mori (Lepidoptera: Bombycidae) by ligature, and observed rhythms in their peripheral tissues under several light conditions. We measured the mRNA expression of period (per) and timeless (tim), which are homologues of Drosophila clock genes that function in the core oscillator of the circadian clock system. The expression of both per and tim significantly changed in the midgut, Malpighian tubules and silk glands of decapitated larvae exposed to photophase and scotophase that were reversed from the original daily light–dark cycle under which the larvae were housed. Under constant darkness, the daily expression of tim mRNA persisted for at least one cycle in the midgut and silk gland. In addition, an appropriate light stimulus under constant darkness induced a significant phase shift in the endogenous timing system (probably a circadian clock) that determined peak levels of tim mRNA expression in the midgut and silk glands of decapitated larvae. Since light regulated the gene expression rhythm in peripheral tissues of decapitated silkworm larvae, neither the brain nor eyes were essential for photoreception to control daily oscillations in these tissues. Thus, peripheral tissues in insects might directly use light even at the larval stage.     

Intracellular Localization of DNA Polymerases in the Oocyte of Starfish, Asterina pectinifera

Oocytes of the starfish, Asterina pectinifera , were separated into karyoplasts and cytoplasts by centrifugation in a sucrose density gradient in the presence of cytochalasin B. More than 90% of the DNA polymerase activity of whole oocytes was recovered in the karyoplasts, and less than 10% in the cytoplasts. DNA polymerase α was specifically localized in karyoplasts. Of the DNA polymerase β activity of whole oocytes, 70–80% was found in the karyoplasts, and about 15% in the cytoplasts. The problem of whether DNA polymerases are localized within germinal vesicles in starfish oocytes is discussed.