## 4 Discussion
### Effects of C.P. pini Infection on the Morphological and Eco-Physiological Functional Traits  
The effect of _C. P. pini_ symptoms was remarkable in some specific morphological traits measured. Although all the studied stands were simultaneously out-planted around the 1970s, the NS-pines living in declining stands had larger DBHs than the S-trees living in the same stands. The results at branch level showed a similar trend, with smaller needle biomasses for symptomatic pines (S-trees) than for non-symptomatic ones (NS-trees). The negative effect of these symptoms on S-trees was also evident in the higher percentage of dry needles and active terminal buds. Our findings agree with other studies that reported slower growing and atrophied needles in trees with abnormal shoot branching as a result of phytoplasma infection in _P. halepensis_, and other naturally infected species such as _Pinus banksiana_, _Pinus mugo_, _Pinus nigra_, _Pinus tubuliformis_, _Abies procera_ and _Tsuga Canadensis_[35; 36; 37; 49]. Contrarily to morphology, the physiological status between the symptomatic (S-trees) and non-symptomatic trees (NS-trees) living in the same stands did not differ for any sampling period. However, the pines living in healthy stands (NA-trees) displayed a better water status (less negative water potential) and greater photochemical efficiency than those living in the declining stands. Therefore, these results pointed out that the stands with better water conditions would favor healthier pine conditions by avoiding the occurrence of declining processes, possibly related to more intense drought conditions. Despite the water potential values recorded in our study reflecting mild stress conditions for Mediterranean species, the water potential for S and NS pines reflected intense stress conditions, since Aleppo pine is an isohydric species with a stomatal closure of about \(-2.5\) MPa [50]. Although pathogens can cause direct tree death through the production of toxic metabolites, they can also induce functional damage by hydraulic failure, photosynthetic inhibition or carbon starvation by altering NSC demand or supply. The relationship between pathogen infection and the physiological mechanisms of drought-induced mortality is complex and depends on the trophic interaction established with the tree [51]. In our study, SS and the total NSC contents in twigs of the pines living in declining stands were higher in NS-trees than in S-trees, while no differences were found for starch. This finding agrees with other works conducted in declining Scots pine populations, where some authors found lower NSC values in defoliated pines than in non-defoliated pines [52; 53]. Other experimental studies in conifer saplings [54] and pine species [55] have found drastic reductions in NSC (especially starch) in stems upon mortality, but have not indicated completely depleted carbohydrate storage [56]. In fact, under similar conditions to those of our study, [PERSON] et al., [17] observed that pines were still able to retain some level of NSC, even when they were in an extremely declined state. Thus, the activation of different biosynthetic routes would require a proportional increment in the metabolism of NSC reserves and carbon allocation by consequently reducing carbohydrate reserves. Our study evidenced that monoterpene and sesquiterpene acted as part of the active primary defense compounds in our populations, which is energetically expensive to build and maintain. Thus, the activation of different biosynthetic routes would require a proportional increment in the metabolism of NSC reserves consequently reducing carbohydrate reserves [20; 57]. Surprisingly, the values for all the fractions were also higher in NS-trees than in NA-trees. In a recent study conducted with two _Pinus_ spp. (_P. contorta_ and _P. Ponderosa_), [PERSON] et al., [58] provided evidence for carbohydrate accumulation (i.e., a long-term precautionary strategy in starch and short-term osmoregulation in soluble sugars) and for growth decline in response to drought.