GERMINATION AND CULTIVATION OF LETTUCE IN THE PRESENCE OF BRACHIARIA GRASS EXTRACTS SUBJECTED TO PRE-TREATMENT WITH SALICYLIC ACID

Abstract

The lettuce is a plant of economic interest, with rapid germination, and is therefore used in experimental protocols. The brachiaria is a grass that can cause allelopathy, interaction between chemical substances that are released by certain organisms and negatively or positively affect the physiological responses of other individuals. Salicylic acid (SA) is a molecule involved in plant defense responses. The objective of this work was to evaluate the germination and initial growth of lettuce under the effect of extracts of Brachiaria decumbens grass submitted to seed pretreatment with SA. The methodology was exploratory, in which lettuce seeds submitted or not to pretreatment with SA 0.1 mM were germinated in the presence or absence of Brachiaria extracts at concentrations of 2%, 4% and 10%; the control group received distilled water. The cultivation time was 7 days for cultivation in Petri dishes and 14 days for cultivation in gerboxes with organic substrate, both grown in a B.O.D. type greenhouse, with controlled temperature and photoperiod. The experiments were organized in completely randomized blocks with four replicates for each treatment in duplicate. The parameters studied were: total germination, germination speed index (GSI), radicle length, and chlorophyll and carotenoid contents. The analysis of the germination speed index results showed no difference between the treatments studied. In substrate culture, the brachiaria extract compromised the germination percentage and AS promoted recovery. In both cultures, the brachiaria extract compromised root growth at a concentration of 2%, AS promoted recovery of root length. No increase in chlorophyll and carotenoid contents was observed in the treatments studied. The brachiaria extract promoted allelopathy and compromised the initial growth of the seedling radicles, phase in which greater sensitivity to chemical compounds occurs. AS probably acted as an antioxidante molecule and promoted positive responses at lower concentrations of the brachiaria extract.