Chinese cinnamon(Cinnamomum cassia) has economic value as an aromatic and medicinal plant, and its bark oil has a very high trans-cinnamaldehyde content. To gain insight into the accumulation of bark oil and the biological mechanisms which permit the accumulation of a high level of aldehydes in C. cassia bark, the morphology and histochemistry of oil cells and the specialization in its walls were assessed by light and fluorescence microscopy. The histochemical tests localized in situ the main chemical classes of metabolites in oil cells, which included aldehydes, lipids and terpenoids. In oil cells the aldehydes distributed in the area surrounding the oil sac were compartmentalized from lipid compounds in the center; the oil sac in an oil cell was attached by multiple cupules rather than one cupule. The autofluorescence of oil-cell walls was attributed to the presence of suberin and lignin, and was confirmed by different methods. The lignified and suberized walls probably serve as protective barriers against the cytotoxicity of high contents of trans-cinnamaldehydeto the surrounding active cells. These results contribute to our knowledge of the structure of oil cells and accumulation of essential oil in Chinese cinnamon bark.
ADP–glucose pyrophosphorylase (AGPase) catalyzes the first limiting step in starch biosynthesis in plants. However, the direct transcriptional activator of the AGPase genes has not yet been determined. We have isolated a WRKY transcription factor cDNA, AtWRKY20, from Arabidopsis thaliana and purified the corresponding protein. Transient expression of AtWRKY20 by particle bombardment enhanced expression of the promoter of ApL3, encoding a sugar-inducible AGPase large subunit gene of A. thaliana, in leaves of A. thaliana. AtWRKY20 bound to the ApL3 promoter in vitro. The expression of AtWRKY20 was strongly induced by sucrose or, to a lesser extent, by mannitol, and the expression pattern of the ApL3 gene mimicked that of the AtWRKY20 gene. Transient expression experiments demonstrated that AtWRKY20 also activated the promoter of Koganesengan ibAGP1 encoding an AGPase small subunit gene of sweet potato var. Koganesengan. A 5’–end deletion analysis revealed a negative regulatory region from –1371 to –641 and a positive regulatory region from –640 to –180 in the Koganesengan ibAGP1 promoter. AtWRKY20 interacted directly with the region between positions –623 and –490 in the Koganesengan ibAGP1 promoter. These results suggest that AtWRKY20 functions directly as a transcriptional activator of the ApL3 promoter and regulates the expression of ApL3 induced by sucrose or osmoticum in A. thaliana. Moreover, AtWRKY20 can enhance the expression of the Koganesengan ibAGP1 promoter directly in sweet potato.
We previously demonstrated that heat-induced spikelet sterility at anthesis could be mitigated by using an early-morning flowering (EMF) line of Oryza sativa L. cv. Koshihikari crossed with wild rice, O. officinalis. Another microclimate factor, high wind velocity, is known to increase the sterility induced by heat. In this study, we evaluated whether EMF rice could mitigate sterility under the combined stresses of heat and wind. Rice plants were exposed to three levels of wind velocity (1.1, 2.2, 3.4 m s-1) from early-morning until 1500 in a glasshouse, where air temperature reached 30ºC at 0800, 34ºC at 1000 and 38ºC around noon. Under these conditions, sterility steadily increased in Koshihikari, ranging from 28.4 to 86.9% as wind velocity increased. However, in the EMF line, low levels of sterility were observed since most spikelets flowered before 1000 when air temperature reached 35ºC, the critical value for causing sterility. These results indicated that the increase in heat-induced spikelet sterility by wind can be potentially mitigated by using EMF rice.
We examined 50 cultivars of sunflower (Helianthus annuusL.) for their resistance to birds in a field experiment to find parental plants for breeding. Two cultivars, Armarvirskij3497 (from Russia) and Line-41 (from Myanmar), had bird-resistant characteristics. The laboratory bird feeding test indicated that the factors associated with bird resistance were globular seed shape and heavy seed coat, because the main bird feeding on sunflower, oriental greenfinch Carduelis sinica, is relatively small and have difficulty pecking large and globular seeds. Although the two cultivars had unfavorable characters such as low tolerance to lodging and late maturity, the oil contents of their seeds was not significantly lower than that in the susceptible cultivar (63M80). The present findings suggest that Armarvirskij3497 and Line-41 are candidate parental materials for breeding bird-resistant sunflower cultivars without losing seed oil productivity.
Low temperature decreases biomass production and yield in rice through a number of physiological and morphological changes. We evaluated biomass production in 22 high-yielding genotypes and four commercial japonica cultivars early after transplanting under field conditions for 2 years. The seedlings were transplanted on 30 April or 1 May (early transplanting, ET) and 4 weeks later (late transplanting, LT). The mean air temperature during the 18 days after transplanting in ET was about 4ºC lower than that in LT in both years. The seedling length was greater in high-yielding japonica varieties than in indica genotypes, whereas the seedling character index (SCI), which is the product of plant age in leaf number and the ratio of the seedling weight to its length, was the highest in the indica genotypes. Varietal differences in biomass production were greater in ET than in LT in all rice genotypes. The biomass at 18 days after transplanting was largest in the japonica high-yielding varieties Kusayutaka and Beko-aoba in both ET and LT. The biomass production of the indica genotypes was found to decrease severely after transplanting at low temperatures although the indica genotypes with high SCIs showed faster leaf emergence than the high-yielding japonica varieties. There was a strong positive correlation between the varietal differences in biomass production and shoot length at 18 days after transplanting in ET in both years. Our study suggests that superior shoot elongation in the high-yielding japonica varieties with large biomass allocation to the stems may be advantageous in maintaining biomass productivity at low temperatures.
Grain nitrogen concentration (N%) is a major determinant of grain quality in winter wheat. The objective of this study was to compare the responses of wheat grain N% to organic manure with those to inorganic fertilizer in long-term experiments. We analyzed the grain N accumulation using soft wheat (Kinunonami) and hard wheat (Yumeshihou) cultivars grown with a high rate of organic manure application (OM; 80 t ha-1 yr-1 for >10 years and 30 t ha-1 yr-1 during the three years of the present study) and with standard (SF; 204–252 kg N ha-1 yr-1) or low (LF; 102–126 kg N ha-1 yr-1) rates of inorganic fertilizer for three years in Japan. The results agreed with previous research on the underlying mechanisms for grain N% under conventional fertilizer management: both sink and source regulation affected N accumulation in grains, and the accumulation of N in grains and of dry matter in grains are independent. Grain N% was significantly higher in the OM treatment than in the SF and LF treatments as a result of lower dry matter accumulation in the grains. High straw N% led to higher N accumulation in grains in the OM treatment during the late grain-filling period in Yumeshihou. Our results suggest that too much organic manure was applied, i.e., more than was required to optimize grain N%, when manure application was designed to produce a grain yield equivalent to that in conventional fertilizer management. We discuss ways to stabilize grain N% under intensive organic manure application.
The root-knot nematode (RKN) is a significant pest in upland farming. We studied the effects of introducing nematode-resistant sweet potato cultivars on crop yield, crop quality, and RKN population dynamics in sweet potato-radish double-cropping systems. Three cropping systems with and without nematicide treatment (6 systems in total) were arranged for a 4-yr field experiment from 2003 to 2006. In two nematode-suppressive cropping systems, highly nematode-resistant J-red, (J) or Sunny red (S) and moderately nematode-resistant Kyushu No. 139 (K139) or Murasakimasari (M) sweet potato cultivars were cropped in alternate years beginning with the former and the latter, and in the non-nematode-suppressive cropping system, nematode-susceptible Kokei No. 14 (K14) and M were cropped in alternate years beginning with the former, from 2003 to 2005. In all cropping systems, K14 was cropped in 2006 to estimate the nematode-suppressive effect of the preceding 3-yr cropping. Introduction of J and S to the cropping system decreased the number of RKNs. In 2006, the extent of injury of K14 was decreased in nematode-suppressive cropping systems. The RKN population density, however, recovered during the cropping of K14 even after cropping of J or S or after nematicide treatment. This suggests that the effects of these measures last for only 1 yr. Nematode injury in radish decreased after nematicide treatment and after cropping of highly nematode-resistant J or S. These results indicate that the introduction of nematode-resistant sweet potato cultivars in cropping systems is effective for reduction of agrochemical use for sustainable agriculture.
Seed tubers of the sweet potato cultivar “Koganesengan” ranging from 40 to 70 g were cut in half at a right angle to the long axis. The half-cut tubers were planted in plastic wide-mouthed bottles, and the bottles were filled with a commercial soil mix. These bottled tubers were kept under natural sunlight in a glasshouse at 25ºC, and watered regularly. After 3–4 wk, the bottled tuber seedlings were transplanted to a field, leaving the tubers in the plastic bottles. Mother tuber enlargement was suppressed in the bottle, but daughter tubers were formed above the bottle, and the mother tuber yield was 4.5% of the total fresh yield of mother and daughter tubers. In the cultivation of tuber seedlings without bottling, the mother tuber yield was 11.2% of the total yield.
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