• Energy Research

Nine-day-old wheat seedlings were treated with NaCl at 75, 150, and 225 mM for 15 days in the absence or presence of 5 mM glycine. NaCl particularly at 150 and 225 mM led to significant reductions in fresh and dry weights, chlorophylls, carotenoids, Ca(2+), K(+), and K(+)/Na(+) ratio. Contrarily, there were significant accumulations in Na(+), malondialdehyde (MDA), H2O2, soluble sugars, and proline concomitant with inhibitions in enzymatic and non-enzymatic antioxidants and in Rubisco. In the meantime, the transcript level of alternative oxidase (AOX) was highly upregulated by NaCl; the upregulation was greatest with the lowest concentration. However, the transcript level of H(+)/Na(+) antiporter exchanger (NHX1) was decreased by 75 and 150 mM NaCl but increased by 225 mM. Similarly, the transcript level of salt overly sensitive 1 (SOS1) was upregulated by only 225 mM. Nonetheless, the application of glycine mostly overcame the varied impacts of NaCl on growth, MDA, H2O2, pigments, metabolites, and elements. Moreover, glycine elevated enzymatic and non-enzymatic antioxidants to reach most likely the levels of the respective control. On the contrary, much induction was detected in Rubisco. The transcript levels of AOX, NHX1, and SOS1 were further upregulated; the upregulation of AOX was most pronounced with the highest NaCl concentration in the presence of glycine and only with 75 and 150 mM NaCl for NHX1 and SOS1. The increase in antioxidants concomitant with the decrease in MDA and H2O2 reveals that ROS scavenging system became more efficient in NaCl-treated wheat following glycine application, concluding that glycine could ameliorate wheat tolerance to salinity. Moreover, lowering Na(+) by glycine and mitigation of the decreased K(+)/Na(+) ratio synchronous with recovery in growth reduction and stimulation of AOX, NHX1 and SOS1 may emphasize the role of glycine in stimulating gene expression for raising wheat tolerance to NaCl.

Rice has shallow, weak roots, but it is unknown how much increase in yield potential could be achieved if the root/shoot ratio is corrected. Removing all tillers except the main one, in a japonica (Sakha 101) and an indica (IR64) rice cultivar, instantly increased the root/shoot ratio from 0.21 to 1.16 in Sakha 101 and from 0.16 to 1.46 in IR64. Over 30 days after detillering, the root/shoot ratios of the detillered plants decreased to 0.49 in Sakha 101 and 0.46 in IR64 but remained significantly higher than in the controls. The detillered plants showed two‐ or fourfold increase in the main tiller fresh weight, as a consequence of more positive midday leaf relative water content (RWC), and consistently higher rates of stomatal conductance and photosynthesis, but not transpiration, compared with the controls. The enhanced photosynthesis in Sakha 101 after detillering resulted from both improved water status and higher Rubisco contents whereas in IR64, increasing the Rubisco content did not contribute to improving photosynthesis. Detillering did not increase the carbohydrate contents of leaves but prevented starch depletion at the end of grain filling. The leaf protein content during vegetative and reproductive stages, the grain filling rate, the number of filled grains per panicle were greatly improved, bringing about 38.3 and 35.9% increase in the harvested grain dry weight per panicle in Sakha 101 and IR64, respectively. We provide evidence that improving the root performance by increasing the root/shoot ratio would eliminate the current limitations to photosynthesis and growth in rice.