Water Deficit at Vegetative Stage Induces Tolerance to High Temperature during Anthesis in Rice.

BACKGROUND: Crop yields have been affected by many different biotic and abiotic factors. Generally, plants experience more than one stress during their life cycle, and plants can tolerate multiple stresses and develop cross-tolerance. The expected rise in atmospheric CO2 concentration ([CO2]) can contribute to cross-tolerance. Priming is a strategy to increase yield or to maintain yield under stress conditions. Thus, our objective was to evaluate if priming the rice plants with water deficit during the vegetative stage can induce tolerance to heat stress at anthesis and to evaluate the contribution of e[CO2]. METHODS: The experiment was arranged in a completely randomized design in a factorial arrangement. Factor A consisted of the following treatments: water deficit at four-leaf stage (no-stress, and drought stress), heat at anthesis (normal temperature, high temperature), and priming with water deficit at four-leaf stage and heat stress at anthesis; and Factor B was two [CO2] treatments: a[CO2] = 400 ± 40 µmol mol-1 and e[CO2] = 700 ± 40 µmol mol-1. We assessed the effect of the treatments on plant growth, yield, biochemical, and transcriptome alterations. RESULTS: Although e[CO2] affected rice growth parameters, it did not affect the priming effect. Primed plants showed an increase in yield and number of panicles per plant. Primed plants showed upregulation of OsHSP16.9A, OsHSP70.1, and OsHSP70.6. These results showed induced cross-tolerance. CONCLUSIONS: Water deficit at the rice vegetative stage reduces the effect of heat stress at the reproductive stage. Water deficit at the vegetative stage can be used, after further testing in field conditions, to reduce the effect of heat stress during flowering in rice.

Phytostimulation of lowland soil contaminated with imidazolinone herbicides.

The phytostimulation is a phytoremediation technique that can be used to remediate area contaminated with herbicides. It is necessary to select plants with high capacity to stimulate soil microbial activity. The present work aimed at evaluating seven plant species regarding their ability to phytostimulate soil and enhance the degradation of the herbicides imazethapyr, imazapic and imazapyr in a lowland soil. An Alfisol Albaqualf was cultivated with the following species, Canavalia ensiformis, Glycine max, Oryza sativa cultivar PUITÁ INTA CL, Lolium multiflorum, Vicia sativa and consortium Lotus corniculatus + Trifolium repens. The rhizosphere of these plants and non-rhizospheric (uncultivated soil) as a control were contaminated in laboratory with analytical standart of the three herbicides, at rates of 0, 150, 300 and 750 g a.i. ha-1, in separate assays. Biodegradation was estimated by quantifying C-CO2 production and through analysis of herbicides residues in soil using liquid chromatography. Results show that biodegradation of herbicides imazethapyr, imazapic and imazapyr was higher in vegetated soil than in unvegetated soil. The leguminous species Canavalia ensiformis, Glycine max, Vicia sativa and consortium of Lotus corniculatus + Trifolium repens showed a great capacity to promote soil microbial, resulting in average biodegradation rates of 91, 92 and 93% for herbicides imazethapyr, imazapic and imazapyr in soil, respectively.