Measuring yield-reducing plant water potential depressions in wheat by infrared thermometry

Summary Measurements of foliage and air wet- and dry-bulb temperatures were made over six differentially irrigated plots of Produra wheat grown at Phoenix, Arizona, in the spring of 1976. These data were used to evaluate a newly developed plant water stress index each day from the initiation of heading to the commencement of senescence. Daily measurements on total plant water potential were also obtained over this period; and after demonstrating how the atmospheric-induced component can be removed from these data, the resultant soil-induced component was plotted as a function of the new water stress index. The result was a simple linear relationship, which was found to be identical to one previously derived for alfalfa. Finally, it was shown that grain yield was directly related to the mean plant water stress index over the reproductive growth period from heading to senescence.Contribution from Agricultural Research, Science and Education Administration, US Department of AgricultureResearch physicist, soil scientist, research physicist, and research entomologist, respectively     

Evapotranspiration and crop coefficient of Populus euphratica Oliv forest during the growing season in the extreme arid region northwest China

Based on successive observation, fifteen-day evapotranspiration (ET_c) of Populus euphratica Oliv forest, in the extreme arid region northwest China, was estimated by application of Bowen ratio-energy balance method (BREB) during the growing season in 2005. During the growing season in 2005, total ET_c was 446.96 mm. From the beginning of growing season, the ET_c increased gradually, and reached its maximum value of 6.724 mm d⁻¹ in the last fifteen days of June. Hereafter the ET_c dropped rapidly, and reached its minimum value of 1.215 mm d⁻¹ at the end of growing season. The variation pattern of crop coefficient (K_c) was similar to that of ET_c. From the beginning of growing season, the K_c value increased rapidly, and reached its maximum value of 0.623 in the last fifteen days of June. Afterward, with slowing growth of P. euphratica, the value dropped rapidly to the end of growing season. According to this study, the ET_c of P. euphratica forest is affected not only by meteorological factors, but by water content in soil.     

The effect of salt stress on Arabidopsis thaliana and Phelipanche ramosa interaction

Salinity and Orobanche or Phelipanche spp. infection are important crop stress factors in agricultural areas. In this study, we investigated the effect of salt stress on Phelipanche ramosa seed germination and its attachment onto Arabidopsis thaliana roots. We also evaluated the effect of both stresses on the expression of genes regulated by abiotic and biotic stresses. According to our results, high concentration of NaCl delayed P. ramosa seed germination in the presence of a strigolactone analogue (GR24). A similar pattern was observed in the presence of A. thaliana plants. Furthermore, we found that salt‐treated A. thaliana seedlings were more sensitive to P. ramosa attachment compared with the untreated plants, indicating that there was a positive correlation between salt sensitivity and the ability of P. ramosa to infect A. thaliana plants. At the molecular level, a synergystic effect of both salt and P. ramosa stresses was observed on the cold‐regulated (COR) gene expression profile of treated A. thaliana seedlings. Our data clarify the interaction between parasitic plants and their hosts under abiotic stress conditions.