Drought and high temperature stress are the major limitation for the crop productions. Proline as osmoregulator in wheat plant under these stresses was studied through field experiments. The experimental design was randomized complete block with four factors i.e. the environment (2008-09 and 2009-10), sowing management (Planting windows PW’s; PW1, PW2, PW3, PW4 and PW5), genotypes (Chakwal-50, Wafaq-2001 and GA-2002) and locations (Islamabad, Chakwal and Talagang) replicated four times. Proline contents measures at anthesis stage of wheat crop depicted significant differences in response to treatments and among locations maximum value recorded at Talagang (39.13 μg g-1) followed by Chakwal (32.36 μg g-1) and Islamabad (24.55 μg g-1). However among PW’s maximum proline recorded for PW5 (35.42 μg g-1) due to exposure of crop to water and high temperature stresses as it was planted late. The inverse relationship of proline with physiological traits and grain yield was observed except for stomatal resistance where it remained positive. In conclusion proline accumulation improved the yield of wheat crop under water and temperature stress by regulating leaf water potential. Since, genotypes Chakwal-50 accumulated highest proline contents in present studies therefore; it needs to be considered for recommendation under stress conditions.
We evaluated the effect of projected increasing temperatures due to climate change on the yield and quality of rice, as well as the effectiveness of shifting the transplanting date as an adaptation measure, throughout Japan. As an indicator of rice quality, we adopted the heat stress index HD_m26, which is related to the decreased percentage of first grade rice due to high temperature, calculated as the cumulative temperature within 20 days after the heading date. We used a process-based rice growth model to assess the effect. We implemented the model for the period 1981-2100, and shifted the transplanting dates at 7-day intervals from -70 to +70 days from the standard transplanting date. The estimated yield was categorized into three classes with different degrees of quality degradation risk according to values of HD_m26. Relative to the current transplanting date, nationwide total production was estimated to increase slightly in most climate change scenarios, although the proportion of production with quality degradation risk may increase with the rise in temperature. It may be possible to avoid this increased risk while maintaining total production by selecting an optimum transplanting date in consideration of both yield and quality. However, a large decrease in yield was found in some areas, suggesting that the current rice producing regions in Japan would become separated into suitable and unsuitable areas as temperatures increase.
To investigate the short-term effects of grassland renovation on carbon dioxide (CO2) exchange of intensively managed grasslands in Japan, we conducted CO2 flux measurements during the renovation process by using the eddy covariance and closed chamber methods in 2007, 2012, and 2013. The flux measurements were conducted at three grassland fields: two fields used for cutting, one receiving only chemical fertilizer (CF) and the other receiving composted cattle manure (CM) annually, and one field used for grazing (GM). Chamber measurements revealed flushes of CO2 after plowing (14.45-23.94 μmol m-2 s-1) and subsequent disk harrowing (7.36 μmol m-2 s-1, in CF) followed by rapid drops of CO2 flux, which were local and temporary phenomena. The mean CO2 losses during renovation periods were calculated as 4.52-4.74, 6.00-6.81, and 4.57 g C m-2 d-1 in CF, CM, and GM, respectively; CF and CM calculation is based on eddy covariance measurements, including temporal flux variations and representing footprint areas. The amount of carbon input during renovation including non-harvested grass biomass (stubble and roots) and applied manure was estimated as 2.24-3.50 and 6.17-8.77 Mg C ha-1 in CF and CM, respectively. Among them, carbon derived from plowed roots and manure is presumably resistant in soil, contributing to long-term soil organic carbon (SOC) accumulation. Our results also indicate that grassland renovation work does not affect short-term net CO2 loss significantly, although it affects CO2 emissions to a certain extent. We can therefore say that net CO2 loss during renovation is mainly brought by the absence of vegetation in this site. Grasses contribute SOC accumulation through biomass allocation belowground; and it is thus recommended to shorten grassland renovation period, the duration without photosynthesis, to reduce CO2 loss associated with grassland renovation.
Photosynthetically assimilated carbon (C) is transported from source leaves to fruits depending on their development stage. To examine the translocation of the assimilated C in a shoot with a fruit throughout the development process, we constructed an in-situ13CO2 exposure chamber system for a fruit-bearing apple shoot and measured the assimilation of 13C in leaves and its translocation to the fruit in an early maturing apple (Malus domestica) cultivar ‘Tsugaru’. Fruit-bearing shoots were exposed three times during the development period (early development, fruit development, and mature stages) to 13CO2 for 1 h in the chamber and collected 72 h after exposure, followed by analysis of 13C inventory in each organ (leaves, branch, and fruit). We evaluated the translocation of 13C using two indices: 13C remaining ratio (13C inventory in each plant organ)/(net assimilated 13C during exposure), and 13C distribution ratio (13C inventory in each plant organ)/(total 13C inventory in the shoot). Although the 13C remaining ratio in the fruit during the early development stage was slightly lower than that at the fruit development and mature stages, the ratio at the mature stage was similar to that at the fruit development stage, indicating that the ability of source leaves to allocate photoassimilates to fruit was maintained until fruit maturation. The 13C distribution ratio of the fruit was similar regardless of its development stage, although biomass proportion of fruit increased with the development stages. This suggests that the sink strength of the fruit-bearing shoots of ‘Tsugaru’ may not be altered by fruit development.
Quercus species occur widely in East Asia and are major tree species in Japan. The ground-grown seedlings of Quercusserrata and Quercusmongolica var. crispula were exposed to enriched ozone (ambient + 40 ppbv) over one growing season by using open-top-chambers (OTC), and isoprene emissions from the two tree-species were measured across a growing season by using the leaf cuvette method. The isoprene emission rates of the two species were significantly affected by ozone, and the rate of Q.mongolica was reduced to a greater extent by ozone in October than that of Q.serrata. The stomatal conductance of Q.mongolica was higher than that of Q.serrata and not affected by O3 even in September, suggesting that Q.mongolica absorbed a larger amount of ozone than Q.serrata did. Since the leaf content of the isoprene precursor dimethylallyl diphosphate (DMAPP) was not significantly different between the enriched ozone and filtered air treatments in July and September, isoprene synthase activity in Q.mongolica leaves might have been reduced to a greater extent by the high concentration of ozone due to higher ozone uptake via stomata. Ozone fumigation was also applied to potted Q.serrata seedlings grown in climate chambers to investigate the ozone effect under different growing conditions. The net photosynthetic rate and isoprene emission rate of the potted seedlings were much lower than those of the ground-grown seedlings in the OTC, regardless of the ozone treatments. Between treatments, the isoprene emission rate and DMAPP content were significantly decreased by enriched ozone, suggesting that reduced production of DMAPP is a cause of the decreased isoprene emission. Our two fumigation experiments revealed that the isoprene emission rates of the two Quercus species was decreased by high ozone concentration, but the possible mechanism may not be identical, depending on the experimental conditions.