M orphophysiological adaptations of araucaria to shade

To verify the morphophysiological adaptations of the arauca ria under shading, two experiments were carried out, one in agroforestry environment with two sizes of seedlings and another under controlled shade. In the agr oforestry experiment 124 large a raucaria seedlings were planted: 35 45 cm; and small: 15 25 cm in height, and submitted to two conditions of luminosity: in f ull sun and shading in agroforest. The seedlings were evaluated 18 months after planting for survival, growth, gas exchange, photosynthetic pigments and foliar anatomy. After 23 months of planting the canopy of the agroforestry was parti ally opened and the arauca rias were reassessed at 25 months of planting . In controlled shade the arauca ria seedlings were cultivated for 21 months at four levels of shade: 0% (full sun), 30%, 50% and 80% of total solar radiation. Growth analyzes, photosynthetic pigments, and chlorophyll a fluorescence were performed. The plants under shading were exposed to full sun for a period of 24 hours and the chlorophyll a fluorescence was evaluated. In the agroforestry the seedlings planted in full sun had greater survival, growth, amo unt of pigments and greater photosynthesis, in relation to the shaded seedlings, at 18 months of planting. Large seedlings had greater survival and growth compared to small ones in full sun. Shaded a rauca ria leaves were smaller, less thick and with reduced differentiation of palindromic parenchyma and hypodermis. After opening the canopy there was a rapid resumptio n of the growth of shaded arauca rias, due to the increase of photosynthesis. In the environment with controlled shading, it was observed that in the higher incident radiation the plants presented larger diameter, higher total dry mass, greater root dry mass distribution, higher D ikson quality index, high pigment contents and high transport rate of electrons, demonstrating the highest quality of see dlings under higher radiation. When the shaded plants were exposed to full sun for a period of 24 hours, they significantly increased the rate of electron transport. Under shading the plants showed adaptations, which would be the increase in the amount of chlorophyll and the greater quantum efficiency of photosystem II. These results indicate that the species tolerates strong shading and has high efficiency in the capture and use of light, as it responds quickly when there is gre ater light in the canopy. Ar auca ria seedlings of large size and high light exposure are recommended in intercropping plantations.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Para verificar as adaptações morfofisiológicas da araucária sob sombreamento, foram realizados 2 experimentos, um em ambiente agroflorestal e outro sob sombreamento controlado. No experimento agroflorestal f oram plantadas mudas de araucária de dois tamanho s : 35 45 cm e 15 25 cm de altura, e submetidas a duas condições de luminosidade: em pleno sol e em sombreamento sob agrofloresta. As mudas foram avaliadas 18 meses após o plantio quanto à sobrevivência, crescimento, trocas gasosas, pigmentos fotossintético s e anatomia foliar. Após 23 meses do plantio fez se abertura parcial do dossel da agrofloresta e avaliaram se novamente as araucárias aos 25 meses do plantio. Em sombreamento controlado as mudas de araucária f oram cultivadas por 21 meses em quatro níveis de sombreamento: 0% (pleno sol), 30 %, 50% e 80% da radiação solar total. Foram realizadas análises de crescimento, pigmentos fotossintéticos, e fluorescência da clorofila a . As plantas sob sombreamento foram expostas a pleno sol por um período de 24 horas e foram avaliadas quanto a fluorescência da clorofila a . Na agrofloresta as mudas plantadas em pleno sol tiveram maior sobrevivência, crescimento, quantidade de pigmentos e maior fotossíntese, em relação às mudas sombreadas, aos 18 meses do plantio. As mudas de tamanho grande tiveram maior sobrevivência e crescimento em relação às pequenas em pleno sol. Folhas de araucárias sombreadas apresentaram se menores, menos espessas e com redução na diferenciação de parênquima paliçádico e hipoderme. Após abertura do dossel ocorreu rápida retomada do crescimento das araucárias sombreadas, devido ao aumento da fotossíntese. Em ambiente com sombreamento controlado verificou se que a pleno sol e no sombreamento de 30% as plantas apresentaram maior esdiâmetro, massa seca total, partição de m assa seca para as raízes, índice de qualidade de Dikson, teores d e pigmentos e taxa de transporte d e elétrons, demonstrando serem mudas de qualidade superior Quando as plantas sombreadas foram expostas à pleno sol por um período de 2 4 horas, aumentaram significativamente a taxa de transporte de elétrons. Sob sombreamento as plantas demonstraram adaptações, que seriam o aumento na quantidade de clorofila e a maior eficiência quântica do fotossistema II. Estes resultados indicam que a espécie tolera o forte sombreamento e tem alta eficiência na captação e uso da luz, pois responde rapidamente quando houver maior entrada de luz no dossel. Em plantios consorciados recomenda m se mudas de araucária de tamanho grande e alta exposição luminosa