Aclimatação da maquinaria fotossintética do cafeeiro à alteração da força-dreno e à seca, em função da restrição do volume radicular

Content Provider	Semantic Scholar
Author	Ronchi, Cláudio Pagotto
Copyright Year	2005
Abstract	Seedlings of Coffea canephora (clone 109A) were grown under screenhouse conditions in pots containing 6and 24-L of substrate, which allowed, respectively, a fast or a slow rate of water deficit progression after withholding irrigation. All sampling and measurements were performed when predawn leaf water potential (Ψpd) about -2.0 (mild) and -4.0 MPa (severe water deficit) was reached. This was achieved at 4 and 6 days, or at 12 and 17 days after suspending irrigation, respectively, in plants grown in the small or large pots. Total chlorophyll and carotenoid concentrations were not affected by treatments. Small changes in chlorophyll a fluorescence parameters were observed, but only in plants submitted to severe, slowly-imposed water deficit. Under severe water deficit, proline concentration increased in plants both in small (31%) and large (212%) pots, as compared with control plants. Drought (Ψpd = -4,0 MPa) led to increased electrolyte leakage (183%), irrespective of pot size. Photosynthetic rates decreased by about 44 and 96%, at Ψpd of –2,0 and -4,0 MPa, respectively, in comparison with control plants. However, only minor changes were detected in those parameters in response to the rate of water deficit imposition. Stomatal conductance and leaf transpiration were significantly affected by water deficit only when it was severe. In general, changes in carbohydrate metabolism depended on pot size and, thus, on the rate of water deficit imposition; however, the activities of key enzymes of carbon metabolism (ADP35 Glc pyrophophorylase, acid invertase, sucrose syntase, sucrose-phosphate synthase, fructose2,6-bisphosphatase, starch phosphorylase, PPi:fructose-6-phophate 1-phosphotransferase and glyceraldehyde-3-phosphate dehydrogenase) were only marginally affected by both the rate of progression and severity of water deficit.
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Resource Type	Article