Morphophysiological responses of forest seedling species subjected to different water regimes

Water availability is a limiting factor for the establishment and development of forest species.To understand the appropriate conditions for the initial post-transplanting phase,it is necessary to understand the specific morphophysiological characteristics of the species,such as the leaf water potential and the efficiency of photosystemⅡ.We aimed to identify the influence of different water regimes on the morphophysiological aspects of young plants of two forest species(Cedrela.fissilis Vellozo and Eucalyptus saligna Sm.).Two greenhouse experiments were conducted for 28 days;one for each species.The design was completely randomized,and the treatments consisted of six different water regimes.Leaf water potential(Ψw)and chlorophyll a fluorescence were evaluated every 7 days.At the end of the experiment,morphological attributes(height,collection diameter,root volume,and dry matter)were measured and histological blades were made.The water demand of E.saligna was higher than that of C.fissilis and required greater replacement within a shorter period.The rehydration fromΨw=-2 Mpa allowed for a fast recovery of the young C.fissilis plants(Ψw=-1.5,Fv/Fm=0.796),which indicated good physiological plasticity of this species when submitted to water stress at a level that is not severe.The total dry matter allocation was different among species.Seedlings of E.saligna presented the best responses when submitted to a continuous water supply regime,while C.fissilis seedlings presented the best response under intermittent irrigation conditions.