Abstract
ABSTRACT The objective of this work was to evaluate the plant-water relations, photosynthetic parameters and growth of macaw (Acrocomia aculeata (Jacp.) Lodd. ex Mart.) plants, thus, ten plants were subjected to three successive drought and rehydration cycles and ten other plants were irrigated normally as control. The drought cycles consisted of a suspension of irrigation until the net CO2 assimilation rate (A) reach values lower than 5% of the control, and a rehydration until a plants recover at least 85% of A of the control plants. Reductions in A, stomatal conductance (gs ) and transpiration (E), above 95%, were found with predawn leaf water potential (Ψpd) of -1.85 MPa. After rehydration, the gs and E of plants with and without water stress was not different, however, A presented a significant difference. Leaf water potentials below -0.5 MPa reduced the intracellular and atmospheric CO2 ratio and increased water use efficiency, and values of -1.85 MPa, when both showed an increase and decrease, respectively. The reduction of A and gs was linear and proportional to Ψpd. Total dry matter accumulation reduced by 50% in the plants subjected to drought. The cyclic water stress resulted in reduction of gas exchange and matter accumulation in macaw palm plants; a stomatal limitation of A occurred until Ψpd of -1.85 MPa, and then a non-stomatal limitation.
Highlights
Drought is an abiotic stress that affects plants at various levels, from cells and organs to the whole plant (SKIRYCZ; INZÉ, 2010)
Stomatal closure is one of the first processes induced by water stress in plants, the net CO2 assimilation rate (A) is directly affected (CHAVES et al, 2009)
One of the first effects of a decreased A is the reduction of primary productivity, resulting in growth and dry matter accumulation reductions (CHAVES et al, 2009)
Summary
Drought is an abiotic stress that affects plants at various levels, from cells and organs to the whole plant (SKIRYCZ; INZÉ, 2010). It is a natural weather phenomenon, which consists of less precipitation than expected for a given period of time (AL-TIMIMI; AL-JIBOORI, 2013). The water stress caused by drought causes different biochemical and physiological responses of plants and is the environmental factor that most affects plant growth and production worldwide. Decreases in A, as a response to water stress, are observed in palm trees such as Bactris gasipaes Kunth (OLIVEIRA et al, 2002), Euterpe oleracea Mart. One of the first effects of a decreased A is the reduction of primary productivity, resulting in growth and dry matter accumulation reductions (CHAVES et al, 2009)
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