Makoto Konnai

Promotive effects of 5-aminolevulinic acid on the yield of several crops

The role of 5-aminolevulinic acid (ALA) as a precursor of chlorophyll or a herbicide is well documented. In the present report, to elucidate the physiological effects of ALA, this compound was applied to the foliage of radish at 0.06, 0.18, 0.6, 1.8 and 6 mM. ALA at 0.06ndash;1.8 mM increased the dry weight of radish root (underground part), but injured radish seedlings at 6 mM. Also, the application of ALA at 0.18 and 0.6 mM increased fixation of CO2 in light and decreased release of CO2 in darkness.Furthermore, the effects of foliar treatment of ALA on the yield of several crops were also evaluated. The results showed that an application of ALA at low concentrations increased the growth and yield by 10ndash;60percnt; over the control on kidney bean, barley, potato and garlic.These results suggest that ALA has plant growth regulating properties at low concentrations and may enhance agricultural productivity.

New Physiological Effects of 5-Aminolevulinic Acid in Plants : The Increase of Photosynthesis, Chlorophyll Content, and Plant Growth

5-Aminolevulinic acid (ALA) promoted the growth and yield of several crops and vegetables at concentrations lower than those eliciting herbicidal responses, i.e., less than 1.8 mm by foliar spray and 60 μm by root soaking. To evaluate the physiological action of ALA, the effects of ALA on plants were examined by several bioassay systems at 0.0006-600 μm. ALA at 0.06-6 μm by root soaking increased the growth of rice seedlings in light, but did not affect this in darkness. In horseradish shoot primordia, promotion by ALA was not proportional among total chlorophyll content, chlorophyll concentration, and fresh weight. In the test using pothos, ALA at 0.06 μm elicited the accumulation of chlorophyll, but the photosynthesis of the plants was promoted by treatment together with ALA and nutrients. These results suggest that ALA have a variety of plant physiological effects on chlorophyll synthesis, photosynthesis, and plant growth, and ALA acts as a growth regulator in plants at low concentrations. These effects of ALA were also assumed to be linked to light irradiation and an uptake of fertilizer by plants. However, excess ALA suppressed these effects.

Effects of brassinosteroids on conditioning and germination of clover broomrape (Orobanche minor) seeds

Brassinolide [2α, 3α, 22R,23R-tetrahydroxy-24S-methyl-B-homo-7-oxa-5-α-cholestan-6-one] and its related compounds, brassinosteroids, applied at the early stages of conditioning shortened the conditioning period required before clover broomrape seeds would germinate after exposure to germination stimulants, such as dl-strigol and natural stimulants from red clover (Trifolium pratense L.) root exudate. Brassinosteroids applied after conditioning increased the rate of the seed germination induced by these stimulants. The inhibitory effect of light on seed germination when it was induced by dl-strigol could be overcome by brassinosteroids. Brassinosteroids also eliminated the inhibitory effects of light and dl-strigol applied at the early stages of conditioning. GA3 was also effective in causing seed conditioning and increased the rate of the germination induced by these stimulants. There was a relationship between brassinosteroids and GA3 in many of the experiments conducted. These findings may have practical implications in increasing the effectiveness of applying germination stimulants in the field to soils for ‘suicidal germination’ of broomrape seeds.

Momilactones A and B in Rice Straw Harvested at Different Growth Stages.

Momilactones A and B in rice straw harvested at different growth stages were quantified by HPLC-MS-MS. They increased to their maximal levels at the heading stage and then gradually decreased. In addition, these phytotoxins were found to be relatively easily extracted with water.

Effects of aqueous extract of rice plants (Oryza sativa L.) on seed germination and radicle elongation of Monochoria vaginalis var. plantaginea

Laboratory experiments were conducted to examine the allelopathic potentials of rice plants (Oryza sativa L.) on seed germination and radicle elongation of Monochoria vaginalis (Burm. f.) Presl var. plantaginea (Roxb.) Solms-Laubat. To compare the relative allelopathic potentials of rice plants at different growth stages, aqueous extracts of dried tissues were obtained from the seeds, husks, and seedlings harvested 10, 20, 40 and 120 days after seeding. When M. vaginalis seeds were incubated in solutions containing aqueous extracts, significant increases in the germination rate were observed for all the aqueous extracts except for the extract of 10 d-old shoots at higher dosages. When partitioned with ethyl acetate, the germination-promoter(s) in the aqueous extracts remained in the aqueous phase while some inhibitors were extracted with ethyl acetate. In contrast, aqueous shoot extracts added to the incubation media at the same dosage for promotion of seed germination inhibited radicle elongation of M. vaginalis, indicating that the sensitivity of the weed varies between these two growth stages.

Effect of Jasmonates and Related Compounds on Seed Germination of Orobanche minor Smith and Striga hermonthica (Del.) Benth

Jasmonates and related compounds were found to elicit the seed germination of the important root parasites, clover broomrape (Orobanche minor Smith) and witchweed [Striga hermonthica (Del.) Benth]. The stimulation of seed germination by the esters was more effective than by the corresponding free acids, and methyl jasmonate (MJA) was the most active stimulant among the compounds tested.

Phloroglucinol Derivatives as Potent Photosystem II Inhibitors

Studies on structure/activity relationships of phloroglucinol derivatives that had been designed based on the structures of grandinol and homograndinol. potent photosystem II (PS II) inhibitors in Eucalyptus grandis, revealed that two electron-withdrawing groups which differ by their electron-withdrawing power on a phloroglucinol nucleus were essential for activity. A larger difference in the electron-withdrawing power between the two groups enhanced the activity, and 3-nitro-phloroglucinecarboxamides and the corresponding thioamides were the most active ones when they had proper lipophilic side chains. Their binding domain seems to overlap with those of DCMU and atrazine, whereas they may approach to the site in a similar manner to that of phenol type inhibitors. Accordingly, the phloroglucinol derivatives represent a new type of PS II inhibitors.

Promotion of Flowering in Sagittaria pygmaea Miq. by 2, 6-Diisopropylphenoxyacetic Acid

The flowering of Sagittaria pygmaea Miq. was promoted by 2,6-diisopropylphenoxyacetic acid, as well as by gibberellic acid (GA3). Uniconazole canceled the promotive effect of the phenoxy-acetic acid, while prohexadione shortened the period required for flowering. Endogenous GAs seem to play an important role in the flowering of S. pygmaea, and 2,6-diisopropylphenoxyacetic acid might affect GA biosynthesis or metabolism.

Effects of Plant Growth Regulators on Shoot Growth and Flowering of a Perennial Paddy Weed, Sagittaria Rygmaea Miq.

Plant growth regulators (PGRs) including gibberellins (GAs) were examined for their effects on shoot growth and flowering of a perennial paddy weed, Sagittaria pygmaea Miq. Among PGRs tested, only GAs (A1 A3, A4, and A5), AC-94377 [1-(4-chloro-1,3-dihydro-1,3-dioxo-2H-isoindol-2-yl)cyclohexanecarbox-amide] and 2,6-diisopropylphenoxyacetic acid (DIPA) promoted both shoot growth and flowering. Structural requirements of GAs for promotion of flowering seemed to be different from those for shoot growth of the weed. In addition, since the course of flowering induced by DIPA was clearly different from that observed in plots treated with GA3 or AC-94377, different mechanisms may be involved in promotion of flowering.

Effects of grandinol and related phloroglucinol derivatives on transpiration and stomatal closure

Grandinol, an inhibitor of seed germination and photosynthesis in Eucalyptus sp., inhibits transpiration and stomatal opening. The acylphloroglucinol structure in grandinol seemed to be essential for these activities. Enhancement of activity was achieved by the introduction of a formyl group into the molecule. Therefore, structural requirements for these activities were very similar to that for the inhibition of seed germination and photosynthesis. Other grandinol-related compounds having two electron-withdrawing groups on the phloroglucinol nuclei were also active in these assays.