The upper part of a nodulated soybean root hydroponically cultured in a glass bottle was monitored using a computer microscope under controlled environmental conditions, and the diameter of individual nodules was measured from 10-24 d after planting. The diameter of a root nodule attached to the primary root increased from 1 mm to 6 mm for 2 weeks under nitrogen-free conditions. The increase in diameter of the nodules was almost completely stopped after 1 d of supplying 5 mM nitrate, and was due to the cessation of nodule cell expansion. However, nodule growth quickly returned to the normal growth rate following withdrawal of nitrate from the solution. The reversible depression of nodule growth by nitrate was similar to the restriction of photoassimilate supply by continuous dark treatment for 2 d followed by normal light/dark conditions. In addition, the inhibitory effect of nitrate was partially alleviated by the addition of 3% (w/v) sucrose to the medium. Plant leaves were exposed to (11)C or (14)C-labelled carbon dioxide to investigate the effects of 5 mM nitrate on the translocation and distribution of photosynthates to nodules and roots. Supplying 5 mM nitrate stimulated the translocation rate and the distribution of labelled C in nitrate-fed parts of the roots. However, the (14)C partitioning to nodules decreased from 9% to 4% of total (14)C under conditions of 5 mM nitrate supply. These results indicate that the decrease in photoassimilate supply to nodules may be involved in the quick and reversible nitrate inhibition of soybean nodule growth.

The genetic variation of rice cultivars provides a resource for further varietal improvement through breeding. Some rice varieties are sensitive to benzobicyclon (BBC), a β-triketone herbicide that inhibits 4-hydroxyphenylpyruvate dioxygenase (HPPD). Here we identify a rice gene, HIS1 (HPPD INHIBITOR SENSITIVE 1), that confers resistance to BBC and other β-triketone herbicides. We show that HIS1 encodes an Fe(II)/2-oxoglutarate–dependent oxygenase that detoxifies β-triketone herbicides by catalyzing their hydroxylation. Genealogy analysis revealed that BBC-sensitive rice variants inherited a dysfunctional his1 allele from an indica rice variety. Forced expression of HIS1 in Arabidopsis conferred resistance not only to BBC but also to four additional β-triketone herbicides. HIS1 may prove useful for breeding herbicide-resistant crops.

We previously demonstrated that a novel hydrophilic gamma-tocopherol (gamma-Toc) derivative, gamma-tocopherol-N,N-dimethylglycinate hydrochloride (gamma-TDMG) converts to gamma-Toc in the mouse skin and has a higher bioavailability than gamma-Toc itself. In the present study, we determined whether gamma-TDMG could reduce photo-inflammation in mouse skin, and compared its effectiveness to that of alpha-Toc acetate (alpha-TA). Topical pre- or post-application of 5% gamma-TDMG significantly reduced the formation of edema and tempered the increase in cyclooxygenase-2 (COX-2)-catalyzed synthesis of prostaglandin E2 (PGE2) that were induced by a single dose of UV irradiation of 2 kJ/m2 (290-380 nm, maximum 312 nm). The pre-treatment of mouse skin with 10% alpha-TA had the same anti-inflammatory effect as did gamma-TDMG. In spite of same having the ability to reduce PGE2 levels, the effect of gamma-TDMG pre-treatment on the inhibition of COX-2 mRNA/protein expression was less than that seen with 10% alpha-TA. In contrast, the increase in COX-2 activity seen after UV exposure was reduced more by gamma-TDMG than by alpha-TA, suggesting that the reduction in PGE2 levels might have been due to the direct inhibition of COX-2 activity by gamma-TDMG-derived gamma-Toc. Both Toc derivatives strongly suppressed inducible nitric oxide synthase (iNOS) mRNA expression and nitric oxide (NO) production, both of which play important roles in UV-induced inflammation. Both derivatives also significantly reduced lipid peroxidation in response to UV exposure, though gamma-TDMG's ability in this regard was less than that seen with alpha-TA, which correlated with their abilities to suppress COX-2 expression. Thus, the gamma-TDMG-derived gamma-Toc acts as an antioxidant, suppresses iNOS expression and directly inhibits COX-2 activity, all of which likely play a role in mediating its suppressive effects on photo-inflammation. Our data further suggest that the topical application of gamma-TDMG, a novel hydrophilic gamma-Toc derivative, may be efficacious in preventing and reducing UV-induced inflammation in humans.

The long-term effect of the concentration and duration of application of nitrate from the lower part of soybean roots on the nodulation and nitrogen fixation in the upper part of roots was investigated using a two-layered pot system separating the upper roots growing in a vermiculite medium and the lower roots growing in a nutrient solution. Continuous absence of nitrate (hereafter referred to as "0-0 treatment"), and continuous 1 m~ (1-1 treatment) and 6 -(6-6 treatment) nitrate treatments were imposed in the lower pot from transplanting to the beginning of the maturity stage. In addition, 6 mM nitrate was supplied partially from the beginning of the pod stage till the beginning of the maturity stage (0-6 treatment) or from transplanting till the beginning of the pod stage (6-0 treatment). The values of the total plant dry weight and seed dry weight were highest in the 6-6 treatment, intermediate in the 1-1, 6-0, 0-6 treatments, and lowest in the 0-0 treatment. The values of the nodule dry weight and nitrogen fixation activity (acetylene reduction activity) were lowest in the 6-6 treatment. The value of the nodule dry weight in the upper roots was highest in the plants subjected to the 1-1 treatment and exceeded that in the 0-0 treatment. Total nitrogen fixation activity of the upper nodules per plant at the beginning of the pod stage was also highest in the 1-1 treatment. These results indicated that longterm supply of a low level of nitrate from the lower roots could promote nodulation and nitrogen fixation in the upper part of roots. Withdrawal of 6 m M nitrate after the beginning of the pod stage (6-0 treatment) markedly enhanced nodule growth and ARA per plant in the upper roots at the beginning of the maturity stage when the values of both parameters decreased in the other treatments. The nitrate concentration in the nodules attached to the upper roots was low, including the 6-6 treatment regardless of the stages of growth. This indicated that the inhibitory effect of 6 mM nitrate or promotive effect of 1 mM nitrate supplied from the lower roots was not directly controlled by nitrate itself, but was mediated by some systemic regulation, possibly by the C or/and N requirement of the whole plant.

A new fertilization method with deep placement of slowrelease N fertilizers, such as coated urea and lime nitrogen (LN) (calcium cyanamide) at 20 cm depth was found to promote soy bean seed yield. In the present study, the effect of deep placement of LN was investigated on different parameters such as growth, N accumulation, N 2 fixation activity and yield of soy bean by applying LN at different rates in the rotated paddy field of Niigata, Japan. In addition to the basal fertilizer, ammonium sulphate (16 kg N ha À1 ), deep placement of LN was conducted by applying various amounts such as 50 kg N ha À1 (A50), 100 kg N ha À1 (A100) and 200 kg N ha À1 (A200) at 20 cm depth in separate plots. A 15 N-labelled LN fertilizer was also employed for each of the above treatments to calculate N utilization from LN in separate plots. Soya bean plant growth and N 2 fixation activity were periodically analysed. Both plant growth and N accumulation were found to increase with LN treatment compared with control plants. An increase in N 2 fixation activity was found in the A100 plots. The total seed yield was the highest in the deep placement of LN with A100 (73 g per plant) compared with other treatments. The visual quality of harvested seeds also showed that A100 enhanced the quality of seeds compared with other treatments. Thus, it is suggested that N fertilization management with particular reference to optimum amount of fertilizers is important for maximum growth, N 2 fixation and enhancement of seed yield of soy bean.