Ultrastructural analysis of the loss of desiccation tolerance in germinating Eremanthus erythropappus seeds

Eremanthus erythropappus(DC.)MacLeish is an important forest species native to the Brazilian savanna biome,an environment with well-defined rainy and dry seasons.Its seeds are desiccation tolerant,non-dormant and dispersed at the end of dry season.This exposes them to the first sporadic rains that can trigger germination but the subsequent dry days can compromise survival of the newly germinated seed.This study evaluates if the damages caused by drying of germinating E.erythropappus seeds,at the stage when they have lost desiccation tolerance,are lethal.The percentage of normal seedlings was evaluated when seeds with different imbibition times were dried to their initial water content and then pre-humidified and rehydrated.Desiccation tolerance was fully lost after 0.5 mm of hypocotyl-radicle protrusion(approximately 72 h)when the radicle had root hairs,a possible indicator of sensitivity to desiccation.Disintegration of cell contents and ultrastructural damage to the seeds subjected to drying were observed by electron scanning microscope.Root hairs disappeared after drying,reappearing after pre-humidification,possibly an attempt to increase the surface area of the radicle for water uptake.However,the hypocotylradicle axis became darkened,probably by antioxidant system failure,causing seed death.

Autoregressive spatial analysis and individual tree modeling as strategies for the management of Eremanthus erythropappus

The objectives of this study were to apply statistical techniques to discriminate fertilization treatments of Eremanthus erythropappus（DC.） Mac Leish.through autoregressive modeling, and to develop individual tree models for diameter and crown area（CA） projection to define management strategies for candeia plantations subjected to different fertilization treatments. This is an important tree species originating from the Brazilian Atlantic Rain forest and Savannah biomes, intensively used in the cosmetic industry. Nonetheless, to date, research has not addressed the management of natural stands or plantations of the species. Our experiment was located in Baependi, Minas Gerais, Brazil, and comprised of four randomized blocks and 13 treatments. The treatments consisted of 12 different regimes of fertilization plus a control. Each sample plot was composed of 50 plants plus two border plants in a planting spacing of 2.5 9 2.0 m and undergoing pruning at 5 and 6 years of age. Starting in the second year, total tree height（H） and circumference（at 1.30 m from the ground or breast height, CBH） were measured every 6 months. Starting in the fifth year CA was measured. Tree growth varied by fertilization strategy.Differences were detected by using an autoregressive approach, considering that standard statistical methods were not powerful enough to detect significant differences.Three growth groups were formed, and maximum growth was obtained for treatment 10（NPK, 8-28-16）. Management guidelines are provided based on individual tree models for different fertilization levels.