The photosynthetic response of tobacco plants overexpressing ice plant aquaporin McMIPB to a soil water deficit and high vapor pressure deficit

We investigated the photosynthetic capacity and plant growth of tobacco plants overexpressing ice plant (Mesembryanthemum crystallinum L.) aquaporin McMIPB under (1) a well-watered growth condition, (2) a well-watered and temporal higher vapor pressure deficit (VPD) condition, and (3) a soil water deficit growth condition to investigate the effect of McMIPB on photosynthetic responses under moderate soil and atmospheric humidity and water deficit conditions. Transgenic plants showed a significantly higher photosynthesis rate (by 48 %), higher mesophyll conductance (by 52 %), and enhanced growth under the well-watered growth condition than those of control plants. Decreases in the photosynthesis rate and stomatal conductance from ambient to higher VPD were slightly higher in transgenic plants than those in control plants. When plants were grown under the soil water deficit condition, decreases in the photosynthesis rate and stomatal conductance were less significant in transgenic plants than those in control plants. McMIPB is likely to work as a CO(2) transporter, as well as control the regulation of stomata to water deficits

Barley plasma membrane intrinsic proteins (PIP aquaporins) as water and CO2 transporters

We identified barley aquaporins and demonstrated that one, HvPIP2;1, transports water and CO2. Regarding water homeostasis in plants, regulations of aquaporin expression were observed in many plants under several environmental stresses. Under salt stress, a number of plasma membrane-type aquaporins were down-regulated, which can prevent continuous dehydration resulting in cell death. The leaves of transgenic rice plants that expressed the largest amount of HvPIP2;1 showed a 40% increase in internal CO2 conductance compared with leaves of wild-type rice plants. The rate of CO2 assimilation also increased in the transgenic plants. The goal of our plant aquaporin research is to determine the key aquaporin species responsible for water and CO2 transport, and to improve plant water relations, stress tolerance, CO2 uptake or assimilation, and plant productivity via molecular breeding of aquaporins.</p

Removal of understory dwarf bamboo (Sasa kurilensis) induces changes in water-relations characteristics of overstory Betula ermanii trees

We investigated how removal of understory dwarf bamboo (Sasa kurilensis Makino et Shibata) affected growth and water-use of young Betula ermanii Cham. trees in a secondary forest in northern Japan. We compared current-year shoot morphology, leaf water-relations characteristics and whole-tree water use of B. ermanii trees growing with dwarf bamboo in the understory (intact plot) to those of trees growing where dwarf bamboo was experimentally removed (removal plot). Current-year shoot length and internode frequency increased, while internode length and individual leaf area decreased in response to dwarf bamboo removal. Carbon isotope composition (δ13C) of leaves did not change indicating that leaf water-use efficiency was unaffected by the presence/absence of dwarf bamboo. Pressure-volume analysis indicated that leaves in the removal plot had lower water uptake ability. During mid-summer, trees in the removal plot sustained high sap flow velocity after peaking at midday, while that of trees in the intact plot declined. In addition, whole-tree sap flux and soil-to-leaf hydraulic conductance were both higher for trees in the removal plot. We inferred that the observed changes reflect hydraulic homeostasis of B. ermanii trees to maintain constant water-use efficiency in response to belowground competition with dwarf bamboo. Removal of dwarf bamboo is, therefore, an effective silvicultural prescription to enhance growth of overstory trees by relieving belowground competition for soil water

問3 単純化しすぎた世界 : 科学のプロフェッショナリズムがもたらす期待と脅威

『といとうとい』Vol.0掲載記事「単純化しすぎた世界 : 科学のプロフェッショナリズムがもたらす期待と脅威」を英語訳したも

Summary of habitat characteristics based on concentrations of soil water chemistry using PCA.

Summary of habitat characteristics based on concentrations of soil water chemistry using PCA.</p

Leaf characteristics.

Leaf characteristics.</p