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Hirofumi Hashimoto

Publications and source records attributed to Hirofumi Hashimoto.

5 recordsLinked to original sources
PubMed2003

Climate-driven increases in global terrestrial net primary production from 1982 to 1999.

Recent climatic changes have enhanced plant growth in northern mid-latitudes and high latitudes. However, a comprehensive analysis of the impact of global climatic changes on vegetation productivity has not before been expressed in the context of variable limiting factors to plant growth. We present a global investigation of vegetation responses to climatic changes by analyzing 18 years (1982 to 1999) of both climatic data and satellite observations of vegetation activity. Our results indicate that global changes in climate have eased several critical climatic constraints to plant growth, such that net primary production increased 6% (3.4 petagrams of carbon over 18 years) globally. The largest increase was in tropical ecosystems. Amazon rain forests accounted for 42% of the global increase in net primary production, owing mainly to decreased cloud cover and the resulting increase in solar radiation.

Atmosphere↗
PubMed2003

Reduced allelopathic inhibition of lettuce (Lactuca sativa) growth caused by velvet bean (Mucuna pruriens) under 3D-clinorotation.

Allelopathy between Mucuna pruriens (velvet bean) and Lactuca sativa (lettuce) was studied under 3D-clinorotation. Growth of both roots and shoots of lettuce seedlings was suppressed by the presence of velvet bean. The degree of suppression was less on the clinostat compared to the normal static earth gravity. L-DOPA (L-3, 4-dihydroxyphenylalanine) is known to be a major substance in allelopathy of velvet bean. Amount of L-DOPA diffused out from a sintered filter paper into agar medium was compared between clinorotation and control group, and found no significant difference. It was concluded that some factors related to release, transport, and sensing phenomena of allelopathic substances may be responsible to the new findings in this study.

Biological Transport↗
PubMed2002

[Research plan to study allelopathy under microgravity].

Living organisms interact each others and form ecological system on the earth. Such interactions between organisms and species have been long known, and studied at a global scale. Allelopathy is a phenomenon observed in many plants that emit specific chemicals acting on other organisms, including animals and microorganisms, in either inhibitory or excitatory ways. We propose to study whether phenomena of allelopathy are modified under altered gravity or not. If biosynthesis, emission and sensing mechanism of allelopathic substances would be affected by gravity, many organisms and ecological system might show different behaviors based on the inter-organisms and species interactions under microgravity. In the macroscopic scale, transport of the substances between organisms is largely affected by convection induced by gravity. Furthermore, the fate of allelopathic substances in confined environment differs from that seen on the earth, because of lacking sink compartment for removal and producing exotic bio-active substances by man-made system. We design basic ground experiment to evaluate gravitational effects on allelopathy applying pseudo-microgravity. Our study contributes to the synthesis of ecological system and its control on spacecrafts and extraterrestrial bodies. It also makes possible to sustain qualitative human life even on the ground under confined artificial environment that dominates in many scenes.

Agriculture↗