Photosynthetic water use efficiency (PWUE), stomatal conductance (gs), and water potential were measured at two different positions in the tree crown of two emergent tropical tree species (Shorea beccariana Burck, Dryobalanops aromatica Gaertn. f.). The trees were about 50 m high, in a tropical rain forest in Sarawak, East Malaysia. In both species, gs at the upper crown position at midday was lower than at the lower crown position, even though both positions were exposed to full sunlight; the difference was greater in S. beccariana. Hydraulic limitation occurs in the upper crown position in both species. A midday depression was observed in the photon saturated photosynthetic rate in both species, especially at the upper crown. However, PWUE was markedly higher in the upper crown than the lower crown at midday, even though no morphological adjustment was observed in the leaves; this difference was greater in S. beccariana. and Y. Kitahashi ... [et al.].
The seasonal changes of photosynthesis of cones of Japanese larch (Larix kaempferi Carr.) trees showed that gross photosynthetic rate of young cones (G) was 2-3 µmol m-2 s-1 at surface area unit and PG / RD (dark respiration of cones) peaked about 0.7 in the same period, indicating that 70 % of respiratory CO2 was re-fixed. With maturation, PG and PG / RD sharply decreased. Chlorophyll content in cones was 3-20 % of that in leaves, which made it a limiting factor for photosynthesis and its content was closely correlated with photosynthetic capacity. Although sunken and linearly arranged stomatal organs were found on the scale of young cones, differently from the significant regulation of leaf photosynthesis, these stomata tended to be non-functional since CO2 is not limiting factor for cone photosynthesis. Thus photosynthesis of larch cones is an additional contribution to their development. and W.-J. Wang ... [et al.].
To find the effects of CO2 enrichment on plant development and photosynthetic capacity of nodulated (line A62-1) and non-nodulated (line A62-2) isogenic lines of soybean (Glycine max Merr.), we examined the interactions among two CO2 treatments (36±3 Pa = AC and 70±5 Pa = EC), and two nitrogen concentrations [0 g(N) m-2(land area) = 0N; 30 g(N) m-2(land area) = 30N]. Nodules were found in both CO2 treatments in 0N of A62-1 where the number and dry mass of nodules increased from AC to EC. While the allocation of dry mass to root and shoot and the amount of N in each organ did not differ between the growth CO2 concentrations, there was larger N allocation to roots in 0N than in 30N for A62-2. The CO2-dependence of net photosynthetic rate
(PN) for A62-1 was unaffected by both CO2 and N treatments. In contrast, the CO2-dependence of PN was lower in 0N than in 30N for A62-2, but it was independent of CO2 treatment. PN per unit N content was unaffected by CO2 concentrations. The leaf area of both soybean lines grown in 30N increased in EC. But in 0N, only the nodulated A62-1 showed an increase in leaf area in EC. Nitrogen use efficiency of plants, NUE [(total dry mass of the plant)/(amount of N accumulated in the plant)] in 30N was unaffected by CO2 treatments. In 0N, NUE in EC was lower than in AC in A62-1, and was higher than that at AC in A62-2. Hence, the larger amount and/or rate of N fixation with the increase of the sink-size of symbiotic microorganisms supplied adequate N to the plant under EC. In EC, N deficiency caused the down-regulation of the soybean plant. and T. Nakamura ... [et al.].
The practicality of the portable, non-destructive type nitrogen meter (Agriexpert PPW-3000) was tested on ten forest species. Also investigated was the potential relationship between leaf nitrogen and chlorophyll (Chl) contents and the readings taken with the PPW-3000 and a Chl meter (SPAD-502). There was a significantly positive correlation between the readings of PPW-3000 and N content in the same leaves, whereas the correlation between leaf Chl content and the PPW-3000 values was less positive. Similarly there was a significant positive correlation between actual Chl content and the SPAD-502 readings and the less positive correlation between actual N content and the SPAD-502 readings. Thus using both the PPW-3000 and SPAD-502 enables to determine leaf N and Chl contents simply and non-destructively in the field. and T. Ichie ... [et al.].