Plant Phenotypic Plasticity in Response to Environmental Factors
Figure 2
Leaf trait variations in response to the light gradient from the top to the bottom of the canopy of three evergreen shrubs (Pistacia lentiscus, Phillyrea latifolia, and Quercus ilex) cooccurring in the Mediterranean maquis [46]. All the considered species have significantly thicker sun leaves compared to shade leaves (on an average 0.45 times) due to the palisade parenchyma (61%, mean value), spongy parenchyma (38%, mean value), and the adaxial cuticle (36%, mean value) thickness. The higher leaf consistency (i.e., higher leaf mass area, LMA) of sun leaves can be used as a measure of investment per unit of leaf area in conditions of full sun. Moreover, shade leaves have a lower chlorophyll a to b ratio (Chl a/b) (13%, mean of the considered species) due to the higher chlorophyll b content (89%, mean of the considered species) since it is usually the main component of the LHCP (light-harvesting protein), which is higher in the shade conditions. Sun leaves allocate, on an average, 16% higher nitrogen (N) content than shade leaves reflecting an increase in carboxylating enzymes (RUBISCO) and proteins, responsible for the photosynthetic electron transport in full sun. The phenotypic plasticity of the considered species is higher for leaf physiological traits (0.86), and among them, net photosynthesis () and the photosynthetic nitrogen use efficiency (PNUE) have a larger plasticity (0.96 and 0.93, resp.). The largest phenotypic plasticity of Q. ilex (0.41) among the cooccurring species (0.36, mean value) reflects its wider ecological distribution area. Leaf dry mass (DM), leaf area (LA), specific leaf area (SLA), total chlorophyll a + b content (Chl a +b), chlorophyll to carotenoid ratio (Chl/Car), chlorophyll to nitrogen ratio (Chl/N), net photosynthesis (), stomatal conductance (), water use efficiency (WUE), and leaf water potential at midday () are shown.
