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31.
Rice plants cope with flash floods using either an ‘escape strategy’ involving rapid shoot elongation or a ‘quiescence strategy’ involving survival underwater with minimal activity. To clarify the differences in the response of leaf photosynthesis properties to conditions during and after submergence, two rice cultivars were compared: a non‐shoot‐elongating cultivar IR 67520‐B‐14‐1‐3‐2‐2 (IR67520) and a shoot‐elongating cultivar IR72442‐6B‐3‐2‐1‐1 (IR72442). Twenty‐three‐day‐old seedlings were submerged in 80‐cm‐deep water for 14 days. During submergence, the chlorophyll contents of the upper fully expanded leaf (5th leaf) and newly developed leaf later (6th leaf) and the maximal quantum yield of photosystem II (Fv/Fm) of the fifth leaf decreased earlier in IR72442 than in IR67520. In the submerged sixth leaf, Fv/Fm was higher in IR72442 than in IR67520 at early measurement. Although Fv/Fm of the sixth leaf in submerged IR67520 increased substantially from 2 days post‐submergence, IR72442 decreased because of leaf chlorosis. Therefore, a non‐shoot‐elongating cultivar coped with submergence by inhibiting photodamage and maintaining high chlorophyll content in the leaves. The shoot‐elongating cultivar was able to maintain the photosynthetic capacity of the newly developed leaf during submergence by prompt reduction of chlorophyll and chlorophyll fluorescence in the leaf that developed before submergence. 相似文献
32.
33.
Riparian forests greatly influence aquatic ecosystems by providing shade cover, which controls water temperature and limits
primary production. We examined the relationship between forest cover and summer stream temperature in northernmost Japan.
Heat budget and statistical analyses were employed and the results were compared. Heat budget analysis revealed that the water
temperature would decrease almost linearly from 29°C to 25°C with an increase in forested reaches along a 3.2 km stretch of
the river. Multiple regression analysis by the stepwise method chose only open channel length as a variable to explain the
variation in maximum stream temperature. A sharp increase in stream temperature was noted when riparian forest cover was removed
in short lengths, of up to 1.0km; this increasing trend gradually flattened as the length of open stretch increased. Thus,
even small openings in the riparian canopy resulted in drastic rises in summer stream temperature. The maximum summer temperatures
estimated by the two methods were coincided, and can therefore be accurately estimated by regression analysis. Retrospective
analysis based on the regression equation showed that the maximum summer temperature in 1947 was 6°C lower than at present,
and that a sharp increase occurred from 1947 to 1960, a period of rapid expansion of agricultural land development in the
watershed. 相似文献
34.
T. Ona T. Sonoda K. Ito M. Shibata Y. Tamai Y. Kojima J. Ohshima S. Yokota N. Yoshizawa 《Wood Science and Technology》2001,35(3):229-243
Relationships between cell and pulp properties were investigated by examining the within-tree property variations in Eucalyptus camaldulensis and Eucalyptus globulus. Properties investigated included proportions of ray and axial parenchyma, thickness of cell walls and cell wall percentages.
The characteristics of the ray and axial parenchyma (their proportions and wall thickness) were found to have a significant
influence on all measured pulp properties, including paper strength properties. Multiple regression of pulp properties in
relation to cell properties revealed that nearly all measured pulp properties were explained by cell properties at the 1%
significance level. It was concluded, therefore, that all cell types are important for predicting pulp properties, and it
is strongly recommended that tree breeding programs for Eucalyptus include the measurement of all cell types.
Received 6 July 1999 相似文献
35.
The effects of shoot size and differences in budburst phenology ofQuercus serrata trees on the spatial patterns of galls were investigated for two cynipid species: the sexual generation ofAndricus moriokae and the agamic generation ofAphelonyx glanduliferae. There were marked differences in budburst phenology, but these did not affect the gall density on the tree. The galls of
both cynipids showed a contagious distribution in their respective trees, but different abundance patterns under high gall
density. The mean number of galls ofA. glanduliferae over a shoot size range was positively correlated with shoot size. More galls ofA. moriokae appeared on larger shoots on trees on which many buds had started growing before oviposition by the agamic adults. In the
case of a tree on which a few buds had burst by the time of oviposition, the mean numbers ofA. moriokae galls on shoots of particular size ranges depended on the frequency of shoots in the size class. These results suggest that,
although these cynipids prefer to attack larger shoots within a host tree, they may exhibit plasticity in their preference
in response to changes in budburst phenology of the host plant relative to the time of oviposition. 相似文献
36.
Toru Kohama Nobuya Mizoue Satoshi Ito Akio Inoue Kotaro Sakuta Hiroyuki Okada 《Journal of Forest Research》2006,11(4):235-242
We examined the extent to which direct and indirect measures of light and microsite conditions could explain variation in
tree height and diameter at the base of 6-year-old Cryptomeria japonica trees planted in a group selection opening of about 0.32 ha on a steep slope at Shiiba, Miyazaki Prefecture, southern Japan.
We first used the gap light index (GLI) and soil thickness (ST) as directly measured indices. For an indirect measure of light, we used a between-cohort competition index (BCI) estimated from the position and total height of residual trees. For indirect measures of microsite, we examined topographic
indices (slope, plan and profile curvature, average slope gradient, and relative elevation) derived from digital elevation
models (DEMs) with different resolutions ranging from 2 to 10 m. The multiple linear regression using GLI and ST explained about 45% of variation in tree size, while simple regression using only GLI explained about 35%. The contribution of ST was about half of GLI. The multiple regressions using BCI and the topographic indices did not explain any more variation than using BCI alone (R
2 of about 0.26). We conclude that microsite conditions with shallower soil and steeper slope have negative effects on tree
growth in group selection openings, although the relative importance is smaller than light conditions. More comprehensive
studies considering several openings with more heterogeneous topography including different species are needed to generalize
our growth prediction using the indirect measures, which are useful for practical forest management. 相似文献
37.
Masaki Jinkawa Hirokazu Yamaguchi Kuniaki Furukawa Toshiaki Satake Hiroshi Kobayashi 《Journal of Forest Research》2006,11(2):77-88
For monorail systems, it is very important to ensure the safety of the ground structure. We developed a tram car for slopes
that utilizes the mechanism of the monorail and analyzed the stress of the ground structure that had double rails. First,
we divided the ground structure into seven components, and formulated a procedure for calculating the stress of the ground
structure. As a result, the stress that acts upon the main rail and the main rail connecting part was near the allowable stress,
and each calculated value was within the allowable stress. We measured the stress by running the vehicle, and compared the
measured values with the calculated values. As a result, some measured values were larger than the calculated values. However,
the ratio of measured value to allowable stress was 90% or less. Finally, we calculated the static loading coefficient for
each part, results of which were as follows: main and subrail: 1.1; rail connection part and prop foundation part: 1.0; rail
installation part: 1.3. In the recalculations, it became clear that the recalculated values exceeded the allowable stresses.
These results suggest that we need to review the ground structure materials. 相似文献
38.
Rashmi Kumari Hirokazu Ito Masahiro Takatani Miho Uchiyama Tadashi Okamoto 《Journal of Wood Science》2007,53(6):470-480
Although wood/cellulose-plastic composites (WPC) of low wood/cellulose content have been more accepted worldwide and are promoted
as low-maintenance, high-durability building products, composites containing high wood/cellulose content are not yet developed
on an industrial scale. In this study, flow properties, mechanical properties, and water absorption properties of the compounds
of cellulose microfiber/polypropylene (PP) and maleic anhydride-grafted polypropylene (MAPP) were investigated to understand
effects of the high cellulose content and the dimensions of the cellulose microfiber. The molding processes studied included
compression, injection, and extrusion. It was found that fluidity is not only dependent on resin content but also on the dimension
of the filler; fluidity of the compound declined with increased fiber length with the same resin content. Dispersion of the
composite was monitored by charge-coupled device (CCD) microscope. Increasing the plastic content in the cellulose-plastic
formulation improved the strength of mold in addition to the bond development between resin and filler, and the tangle of
fibers. The processing mode affected the physicomechanical properties of the cellulosic plastic. Compression-molded samples
exhibited the lowest modulus of rupture (MOR) and modulus of elasticity (MOE) and the highest water absorption, while samples
that were injection-molded exhibited the highest MOR (70 MPa) and MOE (7 GPa) and low water absorption (2%). 相似文献
39.
Tetsuji Ota Tsuyoshi Kajisa Nobuya Mizoue Shigejiro Yoshida Gen Takao Yasumasa Hirata Naoyuki Furuya Takio Sano Raul Ponce-Hernandez Oumer S. Ahmed Heng Sokh Vuthy Ma Eriko Ito Jumpei Toriyama Yukako Monda Hideki Saito Yoshiyuki Kiyono Sophal Chann Nang Ket 《Journal of Forest Research》2015,20(6):484-492
40.