Influência do porta-enxerto na eficiência da atividade fotoquímica em mudas enxertadas de videira submetidas ao estresse salino

Abstract

The accumulation of toxic saline ions (Na+ and Cl-) in plants exposed to salinity is associated with photosynthetic restraint due to the closure of stomata and structural and functional disturbances in the photosystems, affecting the photochemical activity. The analysis of chlorophyll fluorescence emission dynamics provides important information about disturbances that effectively limit photochemical efficiency. In this context, the present study aims to evaluate the effects of rootstocks on changes in photochemical activity in grafted seedlings of vines submitted to saline stress. The experiment was carried out at the Federal Rural University of Pernambuco / Academic Unit of Serra Talhada. The grape seedlings, Italy variety grafted on Italy rootstocks (self-grafting) and IAC 572 rootstocks (graft / rootstock: Itália/Itália and Itália /IAC 572) were subjected to salinity by the addition of NaCl (0, 50 and 100 mM ) in the nutrient solution for 25 days in a artificial growth chamber (FITOTRON - Model SGC 120). At the end of the saline treatment, the water potential was measured and the photosynthesis study was performed through CO2 assimilation curves (A / CI) and photochemical activity in response to light. The plants were then collected and the dry mass of roots, stems and leaves measured. The design adopted was the DIC in factorial 2 x 3, two combinations of grafts/rootstocks (Itália/Itália e Itália/IAC 572) and three doses of NaCl (0, 50 and 100 mM) with three replicates. Data were analyzed using descriptive statistics. Where the seedlings of the Itália/Itália combination showed lower intensity of foliar toxicity symptoms (chlorosis, dryness and necrosis), in relation to the grafts grafted on the rootstock IAC 572, when exposed to salinity. The two graft / rootstock combinations adapted the salinity conditions, in order to reduce the impacts caused. The seedlings of the Itália / Itália combination showed lower intensity of foliar toxicity symptoms than the Itália / IAC 572 combination when exposed to salinity. The two combinations of graft / rootstock adapted the conditions of salinity, in order to reduce the impacts caused, by saline treatment. The seedlings from the Itália autograft showed higher values of NPQ when submitted to the treatment of maximum salinity, representing a greater protection of the photosynthetic apparatus by means of the dissipation of excess energy, in relation to the seedlings of the combination Itália / IAC 572. By means of the qP, the PSII and the ETR, the highest integrity of the photochemical apparatus in Itália / Itália combination was demonstrated in conditions of maximum salinity, when compared to the combination Itália / IAC 572.The behavior of the photosynthesis curve (A) in relation to light, showed that changes of the Itália / IAC 572 combination show good results in the absence of salinity. However are relatively more sensitive to saline stress than the seedlings of the Italia/Italia combination. Thus, the study shows that the type of rootstock may be a determining factor for the production of grapevine grafts aiming at salinity resistance.