Physiological, morphological and biochemical responses to shade of Trichloris crinita, a forage grass from the arid zone of Argentina

This work was performed to evaluate to what extent Trichloris crinita, a C4 grass from the arid zone of Argentina, can grow and persist in shaded environments. The goal is to explore the possibility of using this species in re-vegetation programs of arid regions under tree–grass association systems. Physiological, morphological and biochemical parameters were assessed under different levels of shade: 0%, 40% and 65% (i.e. 100%, 60% and 35% of sunlight, respectively). Under 65% shade, herbage yield and the number of tillers per plant were reduced late in the growing cycle (95–170 days after transplanting). Reductions were 65% and 75%, respectively, as compared with the full sunlight treatment. Growth of plants exposed to medium shade (40%) was between the highest shade and full sunlight. In contrast, the chlorophyll content increased significantly as irradiance decreased. This increment is accompanied by a change in growth habit from upright to prostrate fashion under shade conditions. Prostrate forms would enable plants to capture light and energy more efficiently counteracting in part, the depressing effect of shade on growth. Shade did not affect dry matter allocation to different organs. Other examined biochemical parameters (N, forage quality, etc.) were not influenced by shade. T. crinita would not have major growth limitations under forest–grass association in arid lands where trees are planted spaciously.