The photosynthetic assimilates in leaves of Perilla crispa attached to the plant were labeled by treating the leaves with 4C02. When subsequently detached, these leaves exuded a negligible amount of radioactivity from the cut petiole into water. Ethylenediaminetetraacetate (EDTA), citric acid, and ethyleneglycol-bis(f8-aminoethyl ether) N,N'-tetraacetate greatly increased exudation of labeled assimilates into a solution bathing the petioles. The optimal concentration of EDTA was 20 mM, and maximal exudation took place between 2 and 4 hours after excision. Up to 22% of the radioactivity fixed in the leaf was exuded into an EDTA solution as compared to an export of 38% from attached leaves. The amount of radioactivity in the exudate was much reduced at low temperature.Presence of EDTA was required in the collecting solution for only 1 to 2 hours; upon transfer to water, exudation continued as in continuous presence of EDTA. Ca`+ completely inhibited the effect of EDTA.Anatomical studies indicated that callose formation on the sieve plates near the cut surface of the petioles was less in leaves on EDTA than on water.More than 95% of the radioactivity exuded by detached leaves was present in the sugars verbascose, stachyose, raffinose, and sucrose, which are translocated in the phloem of Perilla. Labeled glucose, fructose, and galactinol were detected in the leaf blade and petiole, but not in exudates.The addition of EDTA to a solution bathing the petiole of detached leaves of Chenopodium rubrum and Pharbitis nil also increased the exudation of labeled assimilates. In these two species, label appeared only in a compound that cochromatographed with sucrose.

The aim of this study was to determine the pharmacokinetics and urinary excretion patterns of the soy isoflavones daidzein and genistein in humans. Six healthy men with a mean age of 37 y and a mean body mass index (in kg/m2) of 24 consumed a soybean flour-based meal on two occasions approximately 6 d apart. Blood samples and total urine were collected at intervals for the measurement of daidzein and genistein with HPLC. Isoflavone concentrations rose slowly and reached maximum values of 3.14 +/- 0.36 micromol/L at 7.42 +/- 0.74 h for daidzein and 4.09 +/- 0.94 micromol/L at 8.42 +/- 0.69 h for genistein. Elimination half-lives were 4.7 +/- 1.1 and 5.7 +/- 1.3 h for daidzein and genistein, respectively. The slow increase in plasma concentrations is consistent with the facilitation of absorption by hydrolysis in the small and large intestines of the glycosidic forms of the isoflavones present in soybean-containing foods to their corresponding aglycones. The rate of urinary excretion of daidzein was greater than that of genistein throughout the postmeal period, with mean recoveries of 62 +/- 6% and 22 +/- 4% (P < 0.001) for daidzein and genistein, respectively. However, the ratio of the areas under the plasma concentration versus time curves for genistein and daidzein was equal to the ratio of the concentrations of the respective isoflavones in the soy meal. It is concluded that the bioavailabilities of daidzein and genistein are similar, not withstanding the difference in urinary excretion.

Seasonal control of flowering through responsiveness to daylength shows extreme variation. Different species flower in response to long days or short days (SDs), and this difference evolved several times. The molecular mechanisms conferring these responses have been compared in detail only in Arabidopsis thaliana and rice (Oryza sativa) and suggest that a conserved pathway confers daylength responses through regulation of FLOWERING LOCUS T (FT) transcription by CONSTANS (CO). We studied Pharbitis (Ipomoea nil; formerly, Pharbitis nil), a widely used SD model species and a member of the Convolvulaceae, and showed using transgenic plants together with detailed expression analysis that two putative orthologs of FT (Pn FT1 and Pn FT2) promote flowering specifically under SDs. These genes are expressed only under SDs, and light flashes given during the night reduce their expression and prevent flowering. We demonstrate that in Pharbitis a circadian rhythm set by the light-to-dark transition at dusk regulates Pn FT expression, which rises only when the night is longer than 11 h. Furthermore, Pharbitis accessions that differ in their critical night-length responses express Pn FT at different times after dusk, demonstrating that natural genetic variation influencing the clock regulating Pn FT expression alters the flowering response. In these assays, Pn FT mRNA abundance was not related to Pn CO expression, suggesting that Pn FT may be regulated by a different transcription factor in Pharbitis. We conclude that SD response in Pharbitis is controlled by a dedicated light sensitive clock, set by dusk, that activates Pn FT transcription in darkness, a different mechanism for measuring daylength than described for Arabidopsis and rice.

No abstract