The Role of Salicylic Acid and Nitric Oxide in Programmed Cell Death and Induced Resistance

Foliar sprays of citric acid and salicylic acid alter the pattern of root acquisition of some minerals in sweet basil (Ocimum basilicum L.)

The effect of foliar application of two levels of citric acid (CA; 0 and 7 mM) and two levels of salicylic acid (SA; 0 and 1 mM) combined with two levels of nutrient solution strength (full strength and half strength) on mineral acquisition by sweet basil were investigated. The experiment was conducted in a randomized block design arrangement with three replications. SA alone reduced the plant height and thickened the stem. Plants supplied with a full strength solution had a ticker stem, produced more biomass, and showed higher values of Fv/Fm. Some changes in the uptake pattern of some nutrients, especially boron and sulfur, were noticed. Higher boron concentrations in leaves were in plants sprayed with a combination of 7 mM CA and 1 mM of SA. Applying combination of CA and SA was more effective than using them individually that suggests an effective synergism between them.

Evaluation of natural and synthetic stimulants of plant immunity by microarray technology

Induction of local defence, as well as systemic resistance, of plants is associated with transcriptional reprogramming. Here we report on defence gene induction by natural and synthetic stimulants of plant immunity. Gene expression changes in Arabidopsis thaliana were monitored in response to several plant immunity stimulants (plant activators) using Northern blotting and an application-based array representing c. 750 genes involved in several aspects of plant defence and/or plant stress. The commercial plant activators Bio-S, Neudo-Vital and PRORADIX have been shown to induce systemic resistance. Here, Neudo-Vital, PRORADIX and Bio-S treatment induced different patterns of salicylic acid (SA) and jasmonic acid (JA) accumulation. Gene induction by these plant activators proved to be very complex. Rather than simply mimicking one of the known defence pathways induced by SA or JA, the response to the plant activators showed aspects of both major defence systems. A general feature was the transient activation of JA biosynthesis genes, combined with a much more sustained SA-associated defence gene induction. Our results demonstrate that plant immunity stimulants activate systemic immunity at the transcriptional level, and they provide insight into the coordinated transcriptional regulation of several classes of plant defence genes.