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Linking bark anatomy to Eucalyptus Physiological Disorder (EPD) in commercial clones
73-87.Views:380Abiotic stresses trigger the Eucalyptus Physiological Disorder (EPD) which poses a threat to planted and native stands. This research seeks links between eucalyptus bark histological features and EPD, in which the descriptive bark anatomy and histochemistry are approached. Barks from 5-year eucalyptus trees, from commercial clones of E. grandis, E. urophylla and its hybrids, were collected at breast height (DBH), and 50% and 75% of the commercial height, and evaluated. The eucalyptus bark consisted of a periderm (or rhytidome) and a secondary phloem with conspicuous solitary sieve tube elements (STE). The outer bark revealed a secondary phloem with collapsed STE, whereas its inner counterpart displayed non-collapsed STEs. A region crowded with calcium oxalate (CaOx) crystals in axial parenchyma, covering the non-collapsed and partially overlapped collapsed secondary phloem, was observed. Eucalyptus barks exhibited similar anatomical organization at DBH, 50% and 75% of the commercial height, irrespective of expected EPD phenotype or scores. Notwithstanding, there are qualitative differences that are associated with the proportion of non-collapsed phloem and phloem with crystals, which were higher in the tolerant clones and in trees with score 0. The more resistant clones or samples with lower EPD scores exhibited a higher proportion of the regions of living phloem, phloem with CaOx crystals, and non-collapsed phloem. These results support the hypothesis that an increased proportion of STE collapse will occur concurrently with elevated EPD scores and are the basis for an ongoing histometric approach.
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Ultrastructural and biochemical aspects of normal and hyperhydric eucalypt
61-69.Views:426Hyperhydricity was observed throughout in vitro multiplication phase of a Eucalyptus grandis clone. Ultrastructural approach of tissue and cell differentiation, izoenzyme patterns, binding protein (BiP) expression, and pigment content were performed. Hyperhydric tissues showed a reduction in cell wall deposition, reduction of membranous organelles, higher cell vacuolation, and more intercellular spaces than its normal counterpart. Additionally, several vesicles were present in hyperhydric cells suggesting the occurrence of organelle autophagy by autophagic vacuole. Lower pigment content, intercellular spaces on the epidermis and the induction of a molecular chaperone (BiP) were observed in hyperhydric phenotype. Evidences of schizolysigenous process of intercellular space formation are compatible with a stress condition. Although plastoglobulli were observed in normal and hyperhydric chloroplasts, they were more evident in the normal ones. Abnormal stomata also reflected a disruptive situation and morphogenesis disturbances which would difficult plant acclimatization. Further observation of the epidermis ultrastructure allows us to conclude that the presence of intercellular spaces on its surface may be constraining the recovery and development of hyperhydric plants. Similarly to BiP, other proteins such as esterase (EST), acid phosphatase (ACP), malate dehydrogenase (MDH) and peroxidase (PDX) are possible to be used as stress markers in in vitro conditions. Our results confirm earlier findings about negative effects of hyperhydricity on in vitro plant morphogenesis and ultrastructure, which in eucalypt is associated with a stressful condition contributing to lower propagation ratios.
