## 1 Introduction  
Owing to sessile nature, plants are continually exposed to abiotic (mainly drought, heat and salinity) and biotic (pathogens and herbivory) stresses whose intensity and frequency are expected to be increased by climate change. The effects of these stresses and how the plants respond to these stressful factors, taken individually, have been extensively studied at both the morpho-physiological and molecular scale [1, 2] and plant community level [3, 4]. However, under field condition, these various biotic and abiotic factors are constantly changing during the plant life cycle and, above all, co-occur in nature [5]. Hence, the plants have to make decisions about fine-tuning their responses to allocate resources efficiently for responding to the more serious and different threats at any given point in time. Different studies have uncovered that plants evoke a \"unique response\" to the combination of abiotic and biotic stresses compared to the single stress [5, 6, 7, 8] revealing that the plants' responses to combined stress pointed out \"a new stress state\" with mostly non-additive effects (i.e., synergistic or antagonistic). For example, insect herbivory antagonized the heat responses in tomato [9], whereas, in this same plant species, drought stress syof specific VOCs in combination with aphid herbivory [10] as well with the larvae of green alder sawfly (_Monsoma pulveratum_) in _Alnus glutinosa_[11]. Drought and simulate herbivory combination synergized some morphological traits of _Pinus sylvestris_, while other ones were antagonized [12]. In addition to the \"new stress state\", the plants' responses to the stress are strictly dependent on the plant traits, genotypes, species, and type, intensity, frequency and duration of the stress suggesting that more investigation is needed for a better understanding of the abiotic and pest herbivore interaction, the least studied among stress combinations. The plants' responses to the individual abiotic and biotic stress have been observed to show a modulation (induced and constitutive) with a strong spatio-temporal component (local or systemic, transient or permanent) that determined a high \"within-plant variation\". For example, the spatial scale of herbivore-induced changes can range from localized at the site of attack [13] to systemic throughout the entire plant or tissue type [14; 15]. Additionally, the light and heat gradients determined different responses within the tree canopy [16] or the nutrient deficiency caused different morpho-physiological responses among the different root types [17; 18]. The temporal scale of the plant responses can also vary: rapid or long term, ontogeny-modulated [19] and, in some cases, even trans-generational responses are evoked for herbivory [20] as well as for abiotic stress [21]. The multiple ecological role of the 'within-plant' variation was recently pointed out in the adaptation to individual abiotic and biotic gradients [22] as well as in the alteration of plant-antagonist interactions [23] so much so that it was proposed as \"functional trait itself\" whose influences on ecosystem functioning are still neglected [24]. In spite of this important role, the within-plant variation in response to the combined stress has not been investigated so far, to the best of our knowledge. Since 2006, the tomato production of the Mediterranean region has been under attack by a newly introduced insect, _Tuta absoluta_, whose larvae feed on leaves, stems and fruits causing severe damage to the tomato with decreases in production both in the field and greenhouse [25]. Previous studies revealed that the low nitrogen levels and drought stress inputs to tomato negatively affected the biological traits of _T. absoluta_[26; 27] but also demonstrated that the N deficiency and drought could be unfavorable to the tomato plants, suggesting that the trade-off between negative impact on _Tuta_ pest and plant growth should be evaluated.