Theoretical and Experimental Plant Physiology

URI permanente para esta coleçãohttps://thoth.dti.ufv.br/handle/123456789/13763

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Photosynthetic induction and activity of enzymes related to carbon metabolism: insights into the varying net photosynthesis rates of coffee sun and shade leaves
(Sociedade Brasileira de Fisiologia Vegetal, 2013-05-21) Martins, Samuel Cordeiro Vitor; Detmann, Kelly Coutinho; Reis, Josimar Vieira dos; Pereira, Lucas Felisberto; Sanglard, Lílian Maria Vincis Pereira; Rogalski, Marcelo; DaMatta, Fábio Murilo
The shade leaves of coffee (Coffea arabica L.) apparently retain a robust photosynthetic machinery that is comparable to that of sun leaves and can fix CO2 at high rates when subjected to high light intensities. This raises the question of why the coffee plant would construct such a robust photosynthetic machinery despite the low photosynthetic rates achieved by the shade leaves at low light supply. Here, we grew coffee plants at 100% or 10% full sunlight and demonstrated that the shade leaves exhibited faster photosynthetic induction compared with their sun counterparts, in parallel with lower loss of induction states under dim light, and were well protected against short-term sudden increases in light supply (mimicking sunflecks). These findings were linked to similar photosynthetic capacities on a per mass basis (assessed under nonlimiting light), as well as similar extractable activities of some enzymes of the Calvin cycle, including Rubisco, when comparing the shade and sun leaves. On the one hand, these responses might represent an overinvestment of resources given the low photosynthetic rates of the shade leaves when light is limiting; on the other hand, such responses might be associated with a conservative behavior linked to the origin of the species as a shade-dwelling plant, allowing it to maximize the use of the energy from sunflecks and thus ultimately contributing to a positive carbon balance under conditions of intense shading.
Aquaporins and the control of the water status in coffee plants
(Sociedade Brasileira de Fisiologia Vegetal, 2013-06-14) Santos, Adriana Brombini dos; Mazzafera, Paulo
Six aquaporin (AQP) homologues were identified in three coffee species (Coffea arabica, C. Canephora, and C. racemosa), including four plasma membrane intrinsic proteins (PIP1;1, PIP1;2, PIP2;1, and PIP2;2) and two tonoplast intrinsic proteins (TIP1;1 and TIP1;2). In order to better understand the role of these genes in coffee, C. arabica cvs Catuaí and Mundo Novo, C. canephora cv. Apoatã, and a graft of Mundo Novo on Apoatã were water stressed, and the expression levels of PIP1;2, PIP2;1, PIP2;2, and TIP1;2 were analyzed in the roots and leaves. The expression of PIP2;1 and PIP2;2 was clearly up-regulated in the leaves and roots by water deficit, suggesting the possible involvement of these genes in controlling the water status of plants and in the post-stress recovery of irrigated plants. The most strongly induced expression in roots was found in both grafted and non-grafted Apoatã plants. Interestingly, the level of PIP2;1 transcripts in roots continued to rise even after the plants were watered and were, therefore, no longer subjected to the water stress, suggesting that this gene may be actively involved in the regulation of water uptake in coffee tree roots, especially when there is a water deficit in the soil.