Variability and Plasticity in Cuticular Transpiration and Leaf Permeability Allow Differentiation of Eucalyptus Clones at an Early Age

Abstract

Background and Objectives. Water stress is a major constraining factor of Eucalyptus plantations’ growth. Within a genetic improvement program, the selection of genotypes that improve drought resistance would help to improve productivity and to expand plantations. Leaf characteristics, among others, are important factors to consider when evaluating drought resistance evaluation, as well as the clone’s ability to modify leaf properties (e.g., stomatal density (d) and size, relative water content at the time of stomatal closure (RWCc), cuticular transpiration (Ec), specific leaf area (SLA)) according to growing conditions. Therefore, this study aimed at analyzing these properties in nursery plants of nine high-productivity Eucalyptus clones. Material and Methods: Five Eucalyptus globulus Labill. clones and four hybrids clones (Eucalyptus urophylla S.T. Blake × Eucalyptus grandis W. Hill ex Maiden, 12€; Eucalyptus urograndis × E. globulus, HE; Eucalyptus dunnii Maiden–E. grandis × E. globulus, HG; Eucalyptus saligna Sm. × Eucalyptus maidenii F. Muell., HI) were studied. Several parameters relating to the aforementioned leaf traits were evaluated for 2.5 years. Results: Significant differences in stomatal d and size, RWCc, Ec, and SLA among clones (p < 0.001) and according to the dates (p < 0.001) were obtained. Each clone varied seasonally the characteristics of its new developing leaves to acclimatize to the growth conditions. The pore opening surface potential (i.e., the stomatal d × size) did not affect transpiration rates with full open stomata, so the water transpired under these conditions might depend on other leaf factors. The clones HE, HG, and 12€ were the ones that differed the most from the drought resistant E. globulus control clone (C14). Those three clones showed lower leaf epidermis impermeability (HE, HG, 12€), higher SLA (12€, HG), and lower stomatal control under moderate water stress (HE, HG) not being, therefore, good candidates to be selected for drought resistance, at least for these measured traits. Conclusions: These parameters can be incorporated into genetic selection and breeding programs, especially Ec, SLA, RWCc, and stomatal control under moderate water stress.

Diversity of Leaf Cuticular Transpiration and Growth Traits in Field-Grown Wheat and Aegilops Genetic Resources

“…This fact was demonstrably related to the leaf area. In a study by Carignato et al [15], the behavior pattern of cuticular transpiration did not differ significantly based on leaf area in terms of differentiation among clones. The reduction in cuticular transpiration mentioned above may be due to increased accumulation of cuticular wax on the leaf surface because the wax layer is a fundamental water transport-limiting barrier of the cuticle, especially when the stomata are fully closed under stress conditions [37].…”

“…Cuticle thickness, ultrastructure, and chemical composition can vary dramatically in a species-, organ-and tissue-specific manner [2,11]. Thus, as they develop their leaves, plants can resort to specific morphological alterations to regulate their water losses, such as changes in the palisade parenchyma thickness [12] or the epidermis and cuticle water tightness [13], the latter being essential to control water losses, especially during drought periods, through cuticular transpiration [14,15].…”

Eucalyptus Productivity Increase in China Comes From Newly Afforested Plantations

“…Eucalyptus is characterized by rapid growth, high yield, stress resistance, barren tolerance, good stem form, and extensive use. In many countries of the world, Eucalyptus is promoted for large-scale afforestation and is one of the four fast-growing genera used for afforestation in the world [1] . The total area of Eucalyptus and Pinus plantations accounts for approximately 30% of the global plantation area [2] .…”

“…(3) a reduction in biological diversity (creation of ecological 'green deserts'); and (4) poor ecological stability [9][10][11][12] . The following questions address these concerns: (1) How can ecological problems related to Eucalyptus plantations be addressed while improving their cultivation patterns and achieving technological innovation? (2) How can the adverse effects of Eucalyptus afforestation in the environment be minimized in a way that allows Eucalyptus plantations to play a role in substituting natural forest harvesting?…”

Genetics and Improvement of Forest Trees

“…Several papers discuss the inheritance of trees and relationship between genotype and environment, which is important to understand for forest tree improvement. Carignato et al [7] report genetic variability in drought resistance among Eucalyptus clones and indicate the possibility of early selection in the nursery. Two papers evaluate selected P. thunbergii clones in terms of pine wood nematode resistance [8,9].…”