Respostas morfofisiológicas de plantas jovens de pau-brasil (Caesalpinia echinata Lam., Leguminosae) à radiação solar

• Autor(a) principal: Mengarda, Liana Hilda Golin
• Data de Publicação: 2010
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da Universidade Federal do Espírito Santo (riUfes)
• Texto Completo: http://repositorio.ufes.br/handle/10/9968
• topic: Ecophysiology; Growth; Photosynthesis; Morphology; Anatomy; Biochemistry; Bioquímica; Caesalpinioideae; Agronomia; Fotossíntese; Morfologia; Anatomia vegetal; Cesalpinácea; Ecofisiologia; Crescimento (Plantas); 57

Caesalpinia echinata Lam. is native specie from the Brazilian Atlantic Forest and is on extinction risk. The informations about the ecophysiological and the successional stage of this specie are contradictory, what dificult its management and conservation. The ecophysiological behavior of young plants of brazilwood affected by light was evaluated through the growth analysis and morphophysiological responses. One-year-old plants were cultivaded under 0%, 50%, 80% artificial shading and natural shading for a period of 392 days, and growth parameters were measured. Higher leaf area, dry mass and relative growth rate were obtained under moderate shade (50%). Under full sunlight the plants showing higher ratio root/shoot and specific leaf mass. Growth was inhibited under 80% artificial shading and natural shade. Plants cultivated under 50% shading were transferred to full sunlight, and at 0, 3, 24, 48 and 192 hours, were measured gas exchange and the potential maximum quantum efficiency of photosystem II (PSII) (FV/FM). Plants leaflets presented burning and abscission, inhibition of net photosynthesis (A) and reduction of FV/FM. Thus, 50% shading presented as ideal lighting conditions for the development of brazilwood young plants. Subsequently, one-year-old plants cultivated under 50% shading were subjected to direct sunlight. At 0, 2, 4, 7, 14, 20, 30, 40, 50, 60, 120 and 180 days were analyzed leaf morphophysiology. Plants transferred to the sunligth showing leaflets abscission after 2 days, and issued new leaves up to 14 days. There was significant increase in specific leaf mass and water content, increasing blade thickness, cuticle, adaxial epidermis and palisade parenchyma. There was reduction in the chlorophyll a/b and chlorophyll/carotenoids ratios. The soluble carbohydrates levels, especially sucrose, increased with plant exposure to full sunlight during 7- 60 days. Glucose and fructose showed higher level at 7 days. Morphoanatomical changes, in the pigments and carbohydrates levels indicate morphophysiological plasticity. However, there was significant reduction of FV/FM, effective maximum quantum efficiency of PSII (FV/F0) and performance index (P.I.) to 14 days. There were observed values below the control until 180 days. Thus, it was observed that full sunlight exposure decreases the plants photochemical efficiency, indicating that C. echinata is not pioneer-sucession species. Growth was inhibited under intense shading, not characterizing the climax specie. Thus, brazilwood has the characteristics of intermediate specie. Although they presented photoinhibition, the young plants have plasticity and capacity of tolerance to high-light stress