Shading as a means of mitigating water deficit in seedlings of Campomanesia xanthocarpa (Mart.) O. Berg

In this research it was hypothesized that Campomanesia xanthocarpa can overcome some level of water deficiency by adjusting physiological parameters and that shading minimizes the water deficit effects while maintaining elevated photosynthetic rates and relative water content of the leaves and makes a resumption of metabolism and growth when the water supply is normalized. The seedlings were submitted to two water regimes (continuous irrigation - CI and intermittent irrigation - II), three shading percentages (0, 30 and 70%) and six evaluation times (Start - T0, 1st Photosynthesis Zero - 1st P0, 1st Recovery - 1st REC, 2nd Photosynthesis Zero - 2nd P0, 2nd Recovery - 2nd REC and END). Plants under water deficit at 0% shading led to a reduction in photosynthetic metabolism, relative water content (RWC), leaf area, number of leaves, and height, especially during the stress periods 1st and 2nd P0. The 30 and 70% shading mitigated the stressful effect of water deficit on C. xanthocarpa seedlings. The results did not confirm the hypothesis that C. xanthocarpa seedlings are intolerant to water deficit since, although sensitive, they presented a potential for recovery of photosynthetic and growth characteristics under all cultivation conditions. It was concluded that that shading minimizes the stressful effects of water deficit

Chlorophyll a fluorescence as an indicator of water stress in Calophyllum brasiliense

The objective of this study was to evaluate chlorophyll a fluorescence as a stress indicator in Calophyllum brasiliense Cambess seedlings grown with different concentrations of abscisic acid (ABA) under intermittent water deficit condition: daily irrigation without ABA (I); daily irrigation + 10 μM ABA (I 10); daily irrigation + 100 μM ABA (I 100); suspension of daily irrigation without ABA (SI); suspension of daily irrigation + 10 μM ABA (SI 10) and  suspension of daily irrigation + 100 μM ABA (SI 100). The intermittent water deficit reduces water status and impairs the photochemical apparatus functioning and seedling quality. The fluorescence measurements helped identify the stress condition of water deficit in the cultivation of C. brasiliense and the beneficial effect of the application of 10 μM of ABA in minimizing stress and facilitating the recovery of seedlings after re-irrigation, while maintaining the integrity and function of the photosynthetic apparatus

Osmotic conditioning and shading on the germination and on the initial growth of <italic>Myracrodruon urundeuva</italic> Allem&#227;o seedlings

<p id="para1">The present work aimed to evaluate the osmotic conditioning and shading on the germination and on the initial growth of aroeira seedlings. The seeds were pre-imbibed in solutions with different concentrations of PEG (polyethylene glycol) and KNO₃ and incubated at 10&#176;C and 20&#176;C temperatures, during 0 (control), 12 and 24 hours. After these periods, the seeds were dried until they reached the initial levels of humidity. After that, they were put for germinating in BOD (Biochemical Oxygen Demand) chambers, at alternated 20-30&#176;C. The control treatment and the pre-conditionings that presented the best results in BOD germination were selected, PEG (-1.0 MPa) + KNO₃ (-1.0 MPa) and KNO₃ (-1.0 MPa), with pre-imbibition for 12 h and incubated in BOD at 20&#176;C. The seeds were sowed on trays and then they were transplanted, keeping under a net covered with 50% and 70% of shading and at sunlight. The osmotic conditioning did not change the seeds germination in BOD, but the highest aerial part size was observed in PEG -1.0 MPa + KNO₃-1.0 MPa treatment. The shading levels at 50% and 70% and the osmotic conditioning with PEG -1.0 MPa + KNO₃-1.0 MPa offered a higher emergence in a greenhouse condition; however, at sunlight the seeds presented a better index of quality on the 145^th day.</p><br><p id="para2">O presente trabalho objetivou avaliar o condicionamento osm&#243;tico e o sombreamento na germina&#231;&#227;o e no crescimento inicial de mudas de aroeira. As sementes foram pr&#233;-embebidas em solu&#231;&#245;es de diferentes concentra&#231;&#245;es de PEG (Polietilenoglicol) e KNO₃ e incubadas em temperatura de 10&#176;C e 20&#176;C durante 0 (controle), 12 e 24 horas. Ap&#243;s estes per&#237;odos as sementes foram secas at&#233; atingirem os n&#237;veis iniciais de umidade. Posteriormente elas foram colocadas para germinar em BOD (Demanda Bioqu&#237;mica de Oxig&#234;nio) na temperatura de 20-30&#176;C. O tratamento controle e os pr&#233;-condicionamentos que apresentaram os melhores resultados de germina&#231;&#227;o em BOD foram selecionados, sendo PEG (-1,0 MPa) + KNO₃ (-1,0 MPa) e KNO₃ (-1,0 MPa), com pr&#233;-embebi&#231;&#227;o por 12 horas e incubados em BOD a 20&#176;C. As sementes foram semeadas em bandejas e posteriormente transplantadas, permanecendo sob telado coberto com sombrite de 50% e 70% de sombreamento e a pleno sol. O condicionamento osm&#243;tico n&#227;o alterou a germina&#231;&#227;o das sementes em BOD, por&#233;m o maior tamanho de parte a&#233;rea foi observado no tratamento PEG-1,0 MPa+KNO₃ -1,0 MPa. Os n&#237;veis de sombreamento de 50 e 70% e o condicionamento osm&#243;tico com PEG-1,0 MPa+KNO₃-1,0 MPa proporcionaram maior emerg&#234;ncia em casa de vegeta&#231;&#227;o, entretanto a pleno sol as mudas apresentaram melhor &#237;ndice de qualidade aos 145 dias.</p

Campomanesia adamantium (Cambess.) O. Berg seed desiccation: influence on vigor and nucleic acids

The aim of this study was to evaluate the sensitivity of Campomanesia adamantium seeds to desiccation by drying in activated silica gel (fast) and under laboratory conditions (slow). To assess the sensitivity of the seeds to desiccation, we used drying with silica gel and drying under laboratory conditions (25 °C), in order to obtain seeds with moisture content of 45, 35, 30, 25, 20, 15, 10 and 5%. The physiological potential of the seeds after desiccation was evaluated by measuring primary root protrusion, percentage of normal seedlings, germination seed index, seedling length, total seedling dry mass, electrical conductivity and DNA and RNA integrities. The C. adamantium seeds were sensitive to desiccation and to a reduction in moisture content to 21.1% or less by desiccation using silica gel, and to 17.2% or less by desiccation under laboratory conditions; impairment of the physiological potential of the seeds was observed at these low moisture content levels. The integrity of the seed genomic DNA was not affected after drying seeds in the two methods. However, drying in silica gel to 4.5% moisture content and drying under laboratory conditions to 5.4% moisture content resulted in the loss of seed RNA integrity