The effects of environmental conditions on formation and suppression of growth of vegetative reproductive organs in field horsetail (Equisetum arvense L.) were examined.
The growth of shoots, elongation of rhizomes and formation of tubers were considerably more active under 16 hour photoperiod conditions than under 8 hour photoperiod conditions (Table 1).
The effects of flooding were also investigated. Flooding treatment immediately after planting of tubers resulted in the dormancy of tubers. Emergent conditions after sprouting of tubers rather promoted shoot growth and rhizome elongation but suppressed tuber formation. Submergence conditions after sprouting of tubers suppressed the growth of shoots, rhizome elongation and tuber formation (Table 2, Fig. 1). Rhizomes were more tolerant to adverse environmental conditions such as high temperature and drought than tubers (Fig. 3, 4).

View full abstract

Several experiments were conducted to analyse the ecological characteristics of dry matter production and the effect of temperature on tuber and rhizome growth in Equisetum arvense L..
The elongation of rhizomes in E. arvense occurred soon after the start of shoot growth. The formation of tubers started two months later than the rhizome elongation. It was found that the photosynthetic rate of E. arvense was not very high compared with that of other plants. The greater part of dry matter production was allocated to rhizomes and tubers, and the dry matter partitioning ratio to these two organs became as high as 75% at the mature growth stage.
Total length of new rhizomes originating from tuber was longer than that from rhizome, except at a high temperature such as 30°C.

View full abstract

The effects of temperature, acidity of medium, aerial conditions and soil moisture conditions on spore germination and development of gametophytes and sterile stems in field horsetail (Equisetum arvense L.) were examined.
Spores could germinate and develop into gametophytes and sterile stems in MS medium within a 60 day period of culture. Spores could germinate in the temperature range from 15 to 30°C, and the highest germination percentage of the spores occurred at 20°C. Spores could germinate in the acidity range of the medium from pH 4.5-6.5 in agar medium. Spores could germinate and develop gametophytes easily in the acidity range of soil from pH 5.3-7.2. Spores could germinate under low oxygen conditions. The soil moisture conditions affected the spore germination and the development of gametophytes and sterile stems. Spores could germinate under soil moisture conditions below pF 2.7 and could develop into gametophytes and sterile stems below pF 2.0.

View full abstract

The diffusion of genes by pollens was analyzed in a natural population of Erigeron philadelphicus that had paraquat resistant genotypes and in an experimental population designed with 4 resistant plants as center, 36 susceptible plants as surroundings and two susceptible satellite blocks. Pollen flow occurs generally in leptokurtic fashion, while our observation indicated a bimodal distribution of diffusion within a 1.2m distance by bees and syrphids in the natural population. Experimental results indicated that although predominant pollinators fly in a near-neighbor fashion, the pattern of gene diffusion over 3m by pollen may be affected by patchy distribution of individual plants in this outbreeding species.

View full abstract

Since volunteer wheat normally sprouts from shed seeds, volunteer wheat control in farming should begin with ecological studies of these seeds. The objectives of this study were to clarify: 1) the forms of seeds shed during combine harvesting, and 2) the effects of these forms of seeds on wheat seed dormancy and longevity in the soil.
Wheat seeds shed during combine harvesting consist of both loose seeds and unthreshed ears (or ear seeds). The head feeding combine lost 98 seeds/m² and 121.7 seeds/m² of loose seeds and ear seeds, respectively, while, the conventional combine lost 18.2 seeds/m² and 42.4 seeds/m² (Fig. 2). This shows that many of seeds from the unthreshed ears fall in the field during combine harvesting.
The results of field experiments showed that the longevity of the seeds of wheat cultivars with a resistance to pre-harvest sprouting was greater than that of cultivars which showed a susceptibility to sprouting. The results also showed that the longevity of unthreshed ear seeds was longer than that of loose seeds in the soil (Table 2, Figs. 4 and 5).
Shed seeds of unthreshed ears during wheat harvesting are numerous, thus making the volunteer problem worse in subsequent barley cultivation.

View full abstract

Cyhalofop butyl, [R-(+)-n-butyl-2-(4-(2-fluoro-4-cyanophenoxy) phenoxy) propionate] is a selective rice graminicide, which can control up to the 5-6 leaf stage of Echinochloa crus-galli by foliar application. Japanese agricultural practices requires development of a granule formulation of cyhalofop butyl; however, the conventional type of extruded granule of the herbicide showed unacceptable bioefficacy. Different commercial ester products on KCl core granules were therefore evaluated in greenhouse trials and field trials in Japan to improve this bioefficacy. Among them, ditridecyl phthalate enhanced the efficacy significantly over that of water treatment of cyhalofop butyl EC formulation. Employment of di-tridecyl phthalate contributed to the high concentration of the graminicide on the water surface, prolonged its half life on hydrolysis and enhanced its uptake into plants. These results suggested that cyhalofop butyl granules containing ditridecyl phthalate would be an effective way to maximize bioefficacy of this herbicide.

View full abstract

Response of two Bidens species (B. tripartita and B. frondosa) to bensulfuron methyl (Methyl=α-(4, 6-dimethoxypyrimidin-2-ylcarbamoylsulfamoyl)-o-toluate) was compared and factors accounting for their differential response were investigated. A greenhouse experiment showed that B. tripartita had greater tolerance to the herbicide than B. frondosa, although the latter had moderate tolerance which was comparable to that of barnyardgrass (Echinochloa crusgalli). Absorption of ¹⁴C from aboveground (shoot) tissue following ¹⁴C-bensulfuron methyl application was more rapid in B. frondosa than in B. tripartita. Absorption from cotyledon was also much greater in B. frondosa and absorbed ¹⁴C was distributed throughout the shoots of the species. Differential foliar absorption and translocation between the Bidens species may partly explain their differential response to bensulfuron methyl.

View full abstract

Red Sprangletop [Leptochloa chinensis (L.) Nees] is one of the most serious grassy weeds in direct seeded rice in Peninsular Malaysia. This study was conducted to investigate the effect of weed density on grain yield and yield components of direct seeded rice. A field experiment was carried out at Sarang Semut, the Training Farm of Muda Agricultural Development Authority (MADA), Kedah. It was found that there was no effect of red sprangletop competition on the vegetative growth of rice plants, since heavy rainfall occurred at seedling stage and inhibited the growth of red sprangletop seedlings. Height and tiller number of rice at 45 days after seeding were not affected by weed competition (Table 1). Among yield components, however, the weight of 1000 filled grains was affected by the competition (Table 2) and panicle number/m² had a significant correlation with red sprangletop density (Fig. 5). Panicle number and number of grains/m² had a significant correlation with the rice yield (Fig. 3 and 4). The yield declined significantly when the rice plants competed with the red sprangletop at a density of 16 plant/m², and was even greater as the weed population increased. More than thirty five percent of yield loss was recorded from the plot which had 40 red sprangletop plants/m², while the highest yield of 4.44t/ha was harvested from the plot which was weed free, as a control. These results suggested that the competition occurred between red Sprangletop and rice from the middle stage of vegetative growth to the grain filling stage.

View full abstract

Influence of environmental conditions on seed production of Scirpus juncoides Roxb. subsp. juncoides and S. wallichii Nees was investigated at Tohoku Natl. Agric. Exp. Stn, Omagari, Akita, Japan. The results were as follows;
1. The number of seeds of S. juncoides and S. wallichii per plant decreased when the time of sowing was delayed, althouh a few seeds were produced even when the seeds were sown on August 11. The number of seeds of both species was reduced by shading, and no seeds of either species sown on August 11 were produced under 65% shading (Fig. 1).
2. The number of stems of S. juncoides and S. wallichii per plant was reduced when the time of sowing was delayed, and it decreased by shading (Fig. 2). The number of seeds per plant was highly correlated with the number of stems and the stem air-dry weight of both species, among the plants sown on different dates or grown under different shading conditions (Tables 4, 5).
3. The number of seeds of S. juncoides was reduced by drainage for 1 month, and the effect of drainage varied with the time of treatment in the growing season. The pattern of seed maturation was also affected by drainage (Tables 2, 3).
4. The one-seed weight of S. juncoides decreased with the delay in the time of harvest, when the seeds were sown before early June. However, when the seeds were sown after the latter part of June, the one-seed weight increased with the delay in the time of harvest (Tables 2, 3).

View full abstract

Involvement of ethylene was investigated in the physiological mechanism of clomeprop [2-(2, 4-dichloro-m-tolyloxy) propionanilide]- or its hydrolytic metabolite DMPA [2-(2, 4-dichloro-m-tolyloxy) propionic acid]-induced electrolyte leakage from radish roots. The treatment of DMPA to radish roots caused increase of electrolyte leakage from the roots, suppression of the root growth and stimulation of ethylene production. Although ethylene action inhibitors, 2, 5-norbornadiene (NBD) and cis-propenylphosphonic acid (PPOH), did not suppress ethylene evolution from the DMPA-treated radish roots for the first 24hrs, these compounds suppressed the electrolyte leakage and to some extent restored the growth of lateral roots. Evan's blue dye tests revealed that death of the root cells occurred 12hr after the DMPA treatment. This indicated that the increase in electrolyte leakage preceded the death of the root cells. These results suggest that the ethylene induced by DMPA is attributable to the leakage of electrolyte from the radish roots.

View full abstract

Photoperiodic response of flowering in M. korsakowii and M. vaginalis was studied using a growth chamber under a strict photoperiod. Under an 8-hour photoperiod, M. korsakowii and M. vaginalis flowered 41 and 48 days after sowing, respectively. No flowering was observed under photoperiods longer than 15 hours. Therefore, both species were considered to be qualitatively short-day plants.
Flowering photoperiod response of M. korsakowii and M. vaginalis was also studied under field conditions by sowing seeds from March to October. In both species the number of days to flowering decreased when the plants were sowed from March to August. No flowering was observed when the plants were sowed in September and October. The time limit of sowing suitable for flowering corresponded to the middle of August in both species.
Intraspecific variation of M. korsakowii and M. vaginalis in the number of days required to flower after sowing was examined under field conditions in Kyoto Prefecture by using many accessions collected from Hokkaido to Kyushu. Both species apparently showed a geographical cline in this physiological character, and the higher the latitude of the collection site was, the earlier the accessions flowered. M. vaginalis flowered earlier than M. korsakowii when a comparison was made between their accessions from similar latitudes.

View full abstract

Effects of environmental factors on the germination, emergence and dormancy breaking of M. korsakowii and M. vaginalis were investigated. Seeds of the two species stored in an outdoor water tank exhibited 100% germination 60 days after the beginning of storage and showed a higher germination percentage than those stored indoors. There was no appreciable difference in the germination percentage of M. korsakowii between seeds stored in outdoor water tank, outdoor upland soil and upland soil at 5°C. However, the seeds of M. vaginalis stored in the outdoor water tank exhibited a far higher germination percentage than those stored under the two other conditions, suggesting that soil moisture is related to the maintenance of seed dormancy (Table 1).
The cardinal temperatures for the germination of seeds released from dormancy were determined by testing the germination percentage at various temperatures. The optimal temperature for germination ranged from 20 to 30°C for M. korsakowii and 25 to 35°C for M. vaginalis. There was no difference in the maximum temperature for both species, 40°C. Seeds of M. korsakowii did not germinate at 10°C, but germinated well at 15C, while those of M. vaginalis did not germinate at these low temperatures and showed only 4% germination even at 20°C (Fig. 1).
The duration of the period from sowing to emergence in the weeds sown from March to July became shorter along with the delay in the sowing time, but when the plants were sown from August to October, it increased. The duration of the period from sowing to emergence was influenced by the total effective temperature (Fig. 2).
Both M. korsakowii and M. vaginalis showed higher seed germination percentages in the light than in the dark (Fig. 3). However, the germination percentages of the former species were always higher than those of the latter species, particularly at lower temperatures. These two species exhibited a high germination percentage under flooded conditions (3 to 5cm in depth), and the germination percentage decreased as the water level decreased and was below the soil surface. Seeds of M. vaginalis were unable to germinate when the water level was maintained at -5cm (Table 2). When buried in soil under flooded conditions, the germination percentage also decreased when the depth of soil burial increased. M. korsakowii and M. vaginalis could emerge within a 3.0cm and 2.0cm depth under submerged conditions, respectively (Fig. 4). M. korsakowii required at least 23 days from flowering to produce viable seeds, while M. vaginalis required 27 days (Fig. 5).

View full abstract

Isozyme analysis by starch gel electrophoresis was used to quantify the genetic variability within and among Japanese populations of M. korsakowii and M. vaginalis. Ten populations of M. korsakowii and fifty populations of M. vaginalis were investigated. Of the three enzyme systems examined, six loci were identified in the two species. One locus was monomorphic and five loci were polymorphic in M. korsakowii. Two loci were monomorphic and four loci were polymorphic in M. vaginalis (Fig. 1 and Table 5). Genetic variability was larger in M. korsakowii populations than in the M. vaginalis ones. M. korsakowii exhibited a higher total genetic diversity (H_T=0.333) and higher intrapopulational genetic diversity (H_S=0.227) than other outcrossing species reported by Loveless and Hamrick.
It is assumed that factors such as breeding systems and local environmental conditions, individually or together, can affect the degree of genetic variability in populations of M. korsakowii and M. vaginalis.

View full abstract