Características fisiológicas e conteúdo de óleos voláteis em folhas de pau-rosa (Aniba rosaeodora Ducke) em diferentes períodos de precipitação, na Amazônia Central

Abstract

In lhe Amazonian forest, lhe rosewood {Aniha rosaeodora Ducke) is dislinguishcd for being an aromatica! species with great commercia! value. above ali. for lhe physiochemical propenies of rich oi! ni linaloí, However, in spile cf lhe imporlance of lhe rosewood. slill lililc knowledge exisls as for lhe physiology and lhe biochemical characlerislics of lhal species. This way, lhe objeclive of this work was to 'ivesligale lhe varialions in lhe physiological characlerislics and lhe volatile oi! concentratio .s and iinalol in leaves of rosewood irees in reply lo diíferem precipilaiion periods. The experimenl was made in len Irees (± 40 years) of lhe planlalion in lhe Adolpho Ducke Foresl Reserve, during lhe period of high (April) and low (Seplember) precipilalion, in the year of 2005. The analyzed variabies were: leaf waler polenliai in lhe pre-dawn (Tam) and midday (^TmdX pressure-volume curves, concenlralion of lhe slorage. lenor of nulrienls, chioroplaslid pigmenl concenlralion, gas exchanges, lenor of lhe volatile oil and of Iinalol in the leaves. The rosewood plants presented high values of the potential hídrico during the rainy period with average of of-0,07 MPa and of of-0,21 MPa; during lhe period of low precipilalion, lhe resuits were of-0,49 MPa and -2.02 MPa, respeclively. In thal period, lhe osmotic polentials in nuli turgidity (4^o) and in full lurgidily (H^ioo) aiso presented decrease, corresponding -0,26 and of-1,81 MPa, respeclively. in relation lo lhe rainy period. This osmotic adjuslmeni mighl have been usea by lhe planis as a slrategy for lhe besl absorpiion of waler during lhe period of smaller precipilalion, parlly, explained by the increase in lhe lenor of the soluble sugars in leaves observed in the same period. in the rosewood leaves. lhe concenlralion of nilrogen (N) didn'l vary, while was observed high malch lenors of phosphorus (P) and of polassium (K) during lhe period of low precipilalion, whal can be relaled lo lhe mainlenance of lhe fundamenlal processes as the breathing. pholosynlhesis and in lhe osmolic regulalion. respeclively. Conlrary lo lhe observed for P and K during ihis period. calcium (Ca) and magnesium (Mg) leveis decreased. For lhe micronutrienles. differences were nol observed in lhe concenlralions. Chiorophyll a contei decreased in lhe dry period. nol happening difference for lhe lenor of lhe chiorophyll h. The decrease of lhe chiorophyll a mighl be relaled wiih lhe degradalion of ihis pigmenl during lhe dry period, as well as duc lhe reduclion of Mg in lhe leaves.lhe pholosynlhesis rale of lhe rosewood was 34.2% higher, during lhe rainy period. in relation lo lhe dry period. lhe breathing rale (Rd). uniike lhe A. increased during lhe period of low precipilalion. On lhe olher hand, lhe slomalal conduclance (gs) decrease and consequcnlK. lhe Iranspiralion rale presented lhe same behavior, with decrease of 46.2%. The rale of eleclrons transport (Jmaxluz) and the carboxylation rate did nol vary during thc periods evalualed. However, the photorespiration rate (Pr) increased during the period of low precipitation, probably to alleviating the excess of energy, The water use efilcicncy (WUK) and the intrinsic water use etficiency (IWUE) also increased, behavior favorable to the plant, once. that the rcductions of the E and of the gs was higher than the decrease of A. To the content of volatile oil. ihis was lov/er during the period of high precipitation, corrcsponding to 2.!%, while in thc period oí low precipitation it was 2.4%. Uniike the oil, high contents were observed during the period of high precipitation differing in approximately 15.3%. Thereíbre. conflrming our original hypotheses rosewood trees shovved physiological characteristics of adaptability to the different regime of precipitation analyzed, particularly for osmotic regulation and in control of stomatal conductancc, likewise for the synthesis of the jíI, being a plant strategy against the water stress or a response to the increase in the leaf phosphorus concentration