Inhibitory Action of an Imidazole Compound on Ecdysone Synthesis in Prothoracic Glands of the Silkworm, Bombyx mori

The precocious pupation was induced either by allatectomy at the time of third ecdysis or by topical application of an imidazole compound (KK-42; 1-benzyl-5-[( E )-2, 6-dimethyl-1, 5-heptadienyl] imidazole) to the fourth (penultimate) instar larvae of the silkworm, Bombyx mori. However, the critical period for KK-42 treatment in induction of precocious pupation was longer than that for allatectomy. The effects of KK-42 depended on the doses applied and a half-maximum dose was estimated to be approx. 10 μg/larva. KK-42 suppressed the increase in hemolymph ecdysteroid titres leading to larval ecdysis in controls. Ecdysteroid levels remained at low levels for about 6 days after the treatment, followed by an increase toward precocious pupation. When the prothoracic glands from the mature fifth instar larvac were incubated in vitro in Grace's medium containing various concentrations of KK-42, secretion of ecdysone into the medium was suppressed depending upon the doses of KK-42 added and a half-inhibition concentration was estimated to be approx. 1 nM. Thus, KK-42 was shown to be an inhibitory agent to ecdysteroid secretion in silkworm larvae.     

Increases in the number of adventitious roots caused by 2-thiouracil and 5-bromodeoxyuridine in Phaseolus mungo cuttings

A cutting of Phaseolus mungoproduced about 4 adventitious rootsat the basal 1 mm region when the basal part of the cuttingwas dipped in water. Rootlets became visible after a 36 hr lagperiod in untreated cuttings. Treatment with 2-thiouracil or5-bromodeoxyuridine increased the number of roots formed onthe cutting and prolonged the lag period. Effects of 2-thiouraciland 5-bromodeoxyuridine were reversed by simultaneously applieduracil and thymidine. The number of roots decreased and thelength of lag period was shortened. The increases in the numberof roots by 2-thiouracil or 5-bromodeoxyuridine was reducedby gibberellic acid, which did not cause a decrease in the numberof roots to be formed on control cuttings. Roots formed at thebasal region seem to suppress further root formation at theupper part of the hypocotyl. Inhibitors used here probably workby blocking the formation of these bottommost roots. (Received April 30, 1971; )     

Reactivation of the Hill reaction of Tris-washed chloroplasts

The Hill reaction of chloroplasts was inhibited by washing themwith 0.8 M Tris buffer. This inhibition was further promotedby adding ferricyanide in the washing medium. When a reducingreagent, such as the 2,6-dichlorophenol indophenol (DCPIP)-ascorbatesystem or the hydroquinone (HQJ-ascorbate system, had been addedto the Tris buffer, Hill reaction activity was unaffected. Hill reaction activity of Tris-washed chloroplasts recoveredup to 70% of the initial level by re-washing the chloroplastswith a preparation medium containing theabove reducing reagents. Photobleaching of carotenoid and chlorophyll is characteristicof Tris-washed chloroplasts. However, reactivated chloroplastsshowed no photobleaching as in the case with intact chloroplasts. (Received April 20, 1970; )     

Morphological and physiological characterization of IAA-less-sensitive and IAA-sensitive phases in rooting of Azukia cuttings

In disbudded epicotyl cuttings taken from light grown 5-dayold Azukia angularis Phaseolus angularis) seedlings, all adventitiousrootlets appeared on the second day of incubation. No root primordiawere observed within the first 24 hr and no increase in thenumber of roots occurred after 48 hr. Puromycin (5.5?10^–5M), p-fluorophenylalanine (1?10^–3M),2-thiouracil (2.3?10^–4M) and 2,6-diaminopurine (2?10^–5M)inhibited rooting when applied to cuttings on the second day,but showed no inhibition when applied on the first day. Unlike these inhibitors, pyrithiamine (7.2?10^–5M) inhibitedrooting when it was applied to cuttings on the first day. A rooting promoting effect was observed with actinomycin D (2.4?10^–6M),2,4-dinitrophenol (3?10^–5M) and p-fluorophenylalanine(1?10^–4M) applied to the cuttings on the first day, whereasindoleacetic acid (1.7?10^–4M) showed its promoting effectmost effectively on the second day. ¹Contribution No. 17 from the Botanical Gardens, Faculty ofScience, University of Tokyo, Tokyo, Japan. (Received June 4, 1969; )     

Non-cyclic photophosphorylation by spinach grana treated with 0.8 M Tris buffer

1. Photophosphorylation was measured with spinach grana sampleswashed by 0.8 M Tris buffer at pH 8.0, which no longer catalyzedthe ferricyanide and NADP HILL reactions with water as the electrondonor. The photophosphorylation with the reaction mixture containing2 10^–4 M 2,6-dichlorophenol indophenol (DCPI) plus above2 10^–3 M ascorbate as the electron donor system insteadof water under anaerobic conditions was, in the most part, dependenton the addition of both PPNR (a nonheme iron protein requisitefor photosynthetic pyridine nucleotide reduction ; spinach ferredoxin)and NADP as the electron acceptor system. However, when ascorbateconcentration only was lowered to 2 10^–4 M, the entirephotophosphorylation proceeded, even in the absence of the electronacceptor system. 2. When the NADP added in the reaction mixture had been reducedby glucose-6-phosphate and glucose-6-phosphate dehydrogenasebefore illumination, the photophosphorylation with 2 10^–4M DCPI plus 6.7 10^–3 M ascorbate decreased to aboutthe same rate as that obtained without NADP. 3. The time course for photophosphorylation in the presenceof NADP was consistent with the time course for the photoreductionof NADP: On the complete reduction of NADP, the photophosphorylationstopped. 4. In the presence of 6.7 10^–3 M dichloropheny 1.1,1-dimethylureaor 3 10^–4 M o-phenanthroline, non-cyclic photophosphorylationwith 2 10^–4 M DCPI plus 6.7 10^–3 M ascorbateas the electron donor system decreased to about half that ofthe control, and the remaining activities were hardly affectedeven at higher concentrations of both inhibitors. The P/2e^–ratios of non-cyclic photophosphorylation in the absence andpresence of ophenanthroline were 0.74 and 0.48, respectively. ¹Present address: Department of Biology, University of California,San Diego, La Jolla, California 92037, U. S. A.     

PROMOTING ACTIVITY OF TERPENIC LACTONES IN PHASEOLUS ROOTING AND THEIR REACTIVITY TOWARD CYSTEINE

Sesquiterpenoids which contain exomethylenes conjugated to -lactonecarbonyl-heliangine, helianginol, pyrethrosin and cyclopyrethrosinacetate—promoted the adventitious root formation on hypocotylsof cuttings taken from light-grown (1900 lux) 6-day old Phaseolusmungo seedlings, but their derivatives in which the methylene-lactone systems are reduced-to the saturated lactones—dihydroheliangine,hexahydro-heliangine, dihydrohelianginol, dihydrocyclopyrethrosinacetate and tetrahydrocyclopyrethrosin acetate—showedno effect on the root formation. As far as the present experiment is concerned, every substancewhich showed promoting activity in Phaseolus rooting reactedwith cysteine and formed an adduct, but any of the substancesincapable of promoting root formation did not react with cysteine.The correlation of promoting activity of terpenic lactones inPhaseolus rooting with their reactivity toward SH groups maythus be demonstrated. ¹ Contribution No. 14 from the Botanical Gardens, Faculty ofScience, University of Tokyo, Tokyo.     

Temporal and spatial variation of forest biomass in relation to stand dynamics in a mature,lowland tropical rainforest,Malaysia

To clarify consistency in the size of carbon pool of a lowland tropical rainforest, we calculated changes in above-ground biomass in the Pasoh Forest Reserve, Peninsular Malaysia. We estimated the total above-ground biomass of a mature stand using tree census data obtained in a 6-ha plot every 2years from 1994 to 1998. The total above-ground biomass decreased consistently from 1994 (431Mgha^–1) to 1998 (403Mgha^–1) (1Mg=10³ kg). These are much lower than that in 1973 for a 0.2ha portion of the same area, suggesting that the the total above-ground biomass reduction might have been consistent in recent decades. This trend contrasted with a major trend for neotropical forests. During 1994–1998, the forest gained 23.0 and 0.88Mgha^–1 of the total above-ground biomass by tree growth and recruitment, respectively, and lost 51.9Mgha^–1 by mortality. Overall, the biomass decreased by 28.4Mgha^–1 (i.e. 7.10Mgha^–1·year^–1), which is almost equivalent to losing a 76-cm-diameter living tree per hectare per year. Analysis of positive and negative components of biomass change revealed that deaths of large trees dominated the total above-ground biomass decrease. The forest biomass also varied spatially, with the total above-ground biomass density ranging 212–655Mgha^–1 on a 0.2-ha basis (n= 30 subplots, 1998) and 365–440Mgha^–1 on a 1ha basis. A large decrease of the total above-ground biomass density (>50Mg per ha per 2years) in several 0.2-ha subplots contributed to the overall decrease in the 6-ha total above-ground biomass. In the present study, we discuss the association between forest dynamics and biomass fluctuation, and the implication for carbon cycling in mature forests with emphasis on forest monitoring and assessments of soil and decomposition systems.     

Dopamine influences locomotor activity in honeybee queens: implications for a behavioural change after mating

Abstract Dopamine has been suggested to be involved in physiological and/or behavioural changes triggered by mating in European honeybee (Apis mellifera) queens but its specific role remains unclear. In the present study, the amounts of dopamine (DA) and its metabolite, N‐acetyldopamine (NADA) are measured, in queens of various ages to clarify the association with locomotor activity. The effects of DA receptor agonist/antagonist drugs on locomotor activity are further investigated. Brain levels of DA and NADA are relatively constant during the period before mating when locomotor activity reportedly increases with age but decreases in 1‐year‐old laying queens with low locomotor activity. Reduced DA and NADA levels are also found in haemolymph of 1–3‐month‐old laying queens. When a DA receptor agonist or antagonist is injected into 6‐day‐old virgin queens, locomotor activity levels increase significantly with 2‐amino‐6,7‐dihydroxy‐1,2,3,4‐tetrahydronaphthalene (agonist), and decreased with cis(Z)‐flupenthixol (antagonist). These results suggest that DA systems are involved in the motor control of honeybee queens, and that the decline in DA levels reduces locomotor activity after mating but increased locomotor activity before mating may be independent of DA levels.