Coffee (Coffea arabica cv. Rubi) seed germination: mechanisms and regulation

Coffee seeds display slow and variable germination which severely hampers the production of seedlings for planting in the following growth season. Little work has been done with the aim to understand the behavior of coffee seeds during germination and there is a lack of information concerning the regulation of the germination process. This thesis addresses questions concerning the mechanism and regulation of coffee seed germination.Initial experiments showed that radicle protrusion in the dark at 30 °C was initiated at around day 5 of imbibition. At day 10, 50% of the seed population displayed radicle protrusion and at day 15 most of the seeds had completed germination. The water uptake by the coffee seeds followed a common triphasic pattern as described for many other species (Chapter 2 and 3). During imbibition the coffee embryo grew inside the endosperm. The cotyledons increased in length by 35% and the axis by 40%, resulting in the appearance of a protuberance in the endosperm cap region. There was an increase in the embryo pressure potential up to day 5 of imbibition followed by a release of turgor thereafter, indicating relaxation of embryonic cell walls (Chapter 3). Light microscopy demonstrated that the cells of the embryonic axis displayed isodiametric growth (swelling) at the beginning of the imbibition process followed by both isodiametric and longitudinal growth later during imbibition. The isodiametric growth coincided with a random orientation of the microtubules whereas longitudinal growth was accompanied by a transversal orientation. Accumulation ofb-tubulin, an increase in the number of 4C nuclei and DNA replication were evident during imbibition. These cell cycle events coincided with the growth of the embryo and the appearance of cell division prior to radicle protrusion. However, cell division was not a pre-requisite for radicle protrusion in coffee seeds (Chapter 5).The endosperm of the coffee seeds possesses polygonal and rectangular cell types located in different parts of the endosperm. The endosperm cap cells have smaller and thinner cell walls than the rest of the endosperm, suggesting that the region where the radicle will protrude is predestined in coffee seed. Low temperature scanning microscopy revealed that during imbibition cells in the endosperm cap became compressed which was followed by a loss of cell integrity, appearance of a protuberance and occurrence of cell wall porosity (Chapter 3). As in many other species, the hemi-cellulose fraction of endosperm cell walls of coffee seeds consists mainly of mannans and galacto-mannans. These polysaccharides are commonly deposited in the cell walls as food reserve. Upon germination, these galacto-mannans are degraded through the action of hydrolytic enzymes, including endo-b-mannanase,b-mannosidase anda-galactosidase resulting in a weakening of the cell walls. The coffee endosperm cap weakens in two steps: cellulase activity correlated with the first step and endo-b-mannanase activity with the second step. Endo-b-mannanase activity appeared first in the endosperm cap and only later in the rest of the endosperm, and coincided with a decrease in the required puncture force and appearance of cell wall porosity. Different isoforms of endo-b-mannanase were found in the endosperm cap and in the rest of the endosperm. The activity ofb-mannosidase increased predominantly in the endosperm cap. However, low levels of endo-b-mannanase andb-mannosidase activities were also observed in the rest of the endosperm and in the embryo prior to radicle protrusion (Chapter 3 and 6). Two partial length cDNA clones encoding for endo-b-mannanase andb-mannosidase, respectively, were isolated from coffee endosperm caps. The deduced amino acid sequences exhibited high homology with those of other endo-b-mannanases andb-mannosidases from plants (Chapter 6). Abscisic acid (ABA) inhibited germination of coffee seeds but not their water uptake, isodiametric growth, increase in 4C nuclei and DNA synthesis in the embryo cells. In the endosperm cap ABA inhibited the second step of endosperm cap weakening, presumably by inhibiting the activities of at least two endo-b-mannanase isoforms. However, ABA had no effect on endo-b-mannanase activity in the rest of the endosperm or on cellulase activity. Two peaks of endogenous ABA occurred in the embryo cells during germination. The first peak was observed at day 2 of imbibition and the second (smaller) peak at day 5 of imbibition. The occurrence of these ABA peaks coincided with the increase in the embryo growth potential and the second step of endosperm cap weakening, which makes these processes possible targets of ABA action (Chapter 3).Exogenous gibberellin (GA 4+7 ) inhibited coffee seed germination. The response to GA 4+7 showed two sensitivity thresholds: a lower one between 0 and 1mM and a higher one between 10 and 100mM. However, it was shown that radicle protrusion of coffee seeds depended on de novo synthesis of GAs. Endogenous GAs were required for embryo cell elongation and the second step of endosperm cap weakening. Incubation of seeds in exogenous GA 4+7 resulted in a loss of embryo viability and the occurrence of dead cells, as observed by low temperature scanning microscopy. We suggest that the inhibition of germination by exogenous GAs is caused by factors that are released from the endosperm cap during or after its weakening. Exogenous GAs greatly accelerated the degradation of the endosperm cap. Factors that are involved in (normal) programmed cell death of the endosperm may reach the embryo during germination, causing cell death in the embryonic axis and, hence, inhibition of radicle protrusion. The results presented in this thesis show that coffee seed germination is controlled both by embryo growth and the second step of endosperm cap weakening (Chapter 4).Finally, the sequence of events during coffee seed germination and their interrelationships are presented and discussed (Chapter 7). The events occurring in embryo and endosperm all followed a two-phase pattern. The first phase occurred during the first 5 days of imbibition and the second phase thereafter, until radicle protrusion. The results make clear that the germination processes are temporally and spatially coordinated and that disturbance of this coordination, as in the presence of GAs, may severely affect seed behaviour

Condicionamento Fisiológico De Sementes De Soja, Componentes De Produção E Produtividade

The Soybean crop is extremely relevant to the Brazilian economy. Priming is a technique that allows improvement of seed quality, especially those of low vigor. Vigor is defined as the ability of the seed to perform adequately when exposed to different environmental conditions. High vigor seeds generate plants with higher emergency speed and superior yield components, favoring into a higher seed yield. The objective of this work was to evaluate the agronomic behavior of soybean plants under field conditions originated from primed seeds with different level of vigor. Yield components and soybean yield were also evaluated. Seed priming in seed with medium vigor positively influences the components (seedling emergence, first pod height, number pods/plant, number of seeds/plant, number of seeds/ pod) and favored productivity of soybean cultivar ‘M7211RR’. Different levels of vigor of soybean seeds cause differences in the number of pods/plant. © 2015, Universidade Federal de Santa Maria. All Rights Reserved.46222723

Variations In Desiccation Tolerance In Seeds Of Eugenia Pyriformis: Dispersal At Different Stages Of Maturation

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Eugenia pyriformis Cambess., known locally as uvaieira, a species of fruit-bearing tree with both pharmacological and gastronomic potential, has seeds which are sensitive to desiccation. The aim of this study was to analyse whether the degree of tolerance to desiccation of uvaieira seeds depends on the stage of maturation of the seeds at shedding. This, in turn, depends on the environmental conditions in which the seeds develop, including the accumulation of degree-days and rainfall in the period. Seeds were collected from the ripe fruit of parent plants located in the states of São Paulo and Minas Gerais, Brazil, submitted to drying and analysed for water content and germination. A completely randomised design was used in a 20 × 3 factorial scheme (source of material x level of drying). The degree of desiccation tolerance differs between region and period of collection, even for the same parent plant when the seeds are collected in different years. The water and thermal conditions of the environment during seed development modify the maturation cycle, the physiological quality and the acquisition of desiccation tolerance. In uvaieira seeds, desiccation tolerance depends on the physiological maturity of the seeds at the time of dispersal, which is associated with the environmental conditions.471118126CAPES, Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Biochemical and bioactive phytonutrients changes in tissues of two cultivars of fresh-cut cassava in stick form under refrigerated storage

The aim of this study was to evaluate the effects of fresh-cut in stick form of two cassava cultivars on their biochemical and antioxidant characteristics, at two harvest times. The fresh cut cassava sticks were packaged in polypropylene, maintained at 5±1ºC, with 90±5% relative humidity for 12 days. The concentration of carotenoids, total soluble phenolic compounds and the activity of phenylalanine ammonia lyase and antioxidant capacity were significantly higher for the sticks of cultivar 'Amarela' cassava than for the sticks of cultivar 'Cacau'. The concentrations of carotenoids, total soluble phenolic compounds, and the activity of phenylalanine ammonia lyase and antioxidant capacity were all significantly greater when harvested at 14-month of age. There was a significant increase in the activity of phenylalanine ammonia lyase during the 12 days of storage at 5ºC. However, there was a decrease in total carotenoids, soluble phenolic compounds, and in the antioxidant capacity of the two cultivars

Anaerobic-aerobic baffled reactor treating real municipal wastewater in a low income community

Inadequate sanitation and poor infrastructure for waterborne sanitation are common in many developing countries. The anaerobic/aerobic baffled reactor (AABR) is a sustainable option for water sanitation in developing countries. In the present study, a 2.50 m AABR reactor working with real municipal wastewater was monitored. Four sequenced chambers, the first three being anaerobic and the fourth aerobic composed the AABR reactor. AABR efficiency and performance were examined during four different periods. Organic and hydraulic load increases were adequately absorbed, provoking no instability in the system and demonstrating good configuration for absorbing organic impacts. The AABR had a promising effect on COD removal, which led removal values of total COD up to 74%, and total suspended solid (TSS) removal up to 79%. Regardless of the value on entering, the pH from the reactor effluent remained close to 7 during the four periods, indicating good stability in the reactor.Peer Reviewe

Abscisic acid controls embryo growth potential and endosperm cap weakening during coffee (Coffea arabica cv. Rubi) seed germination

The mechanism and regulation of coffee seed germination were studied in Coffea arabica L. cv. Rubi. The coffee embryo grew inside the endosperm prior to radicle protrusion and abscisic acid (ABA) inhibited the increase in its pressure potential. There were two steps of endosperm cap weakening. An increase in cellulase activity coincided with the first step and an increase in endo-beta-mannanase (EBM) activity with the second step. ABA inhibited the second step of endosperm cap weakening, presumably by inhibiting the activities of at least two EBM isoforms and/or, indirectly, by inhibiting the pressure force of the radicle. The increase in the activities of EBM and cellulase coincided with the decrease in the force required to puncture the endosperm and with the appearance of porosity in the cell walls as observed by low-temperature scanning electronic microscopy. Tissue printing showed that EBM activity was spatially regulated in the endosperm. Activity was initiated in the endosperm cap whereas later during germination it could also be detected in the remainder of the endosperm. Tissue printing revealed that ABA inhibited most of the EBM activity in the endosperm cap, but not in the remainder of the endosperm. ABA did not inhibit cellulase activity. There was a transient rise in ABA content in the embryo during imbibition, which was likely to be responsible for slow germination, suggesting that endogenous ABA also may control embryo growth potential and the second step of endosperm cap weakening during coffee seed germination

Abscisic acid controls embryo growth potential and endosperm cap weakening during coffee (Coffea arabica cv. Rubi) seed germination

The mechanism and regulation of coffee seed germination were studied in Coffea arabica L. cv. Rubi. The coffee embryo grew inside the endosperm prior to radicle protrusion and abscisic acid (ABA) inhibited the increase in its pressure potential. There were two steps of endosperm cap weakening. An increase in cellulase activity coincided with the first step and an increase in endo-beta-mannanase (EBM) activity with the second step. ABA inhibited the second step of endosperm cap weakening, presumably by inhibiting the activities of at least two EBM isoforms and/or, indirectly, by inhibiting the pressure force of the radicle. The increase in the activities of EBM and cellulase coincided with the decrease in the force required to puncture the endosperm and with the appearance of porosity in the cell walls as observed by low-temperature scanning electronic microscopy. Tissue printing showed that EBM activity was spatially regulated in the endosperm. Activity was initiated in the endosperm cap whereas later during germination it could also be detected in the remainder of the endosperm. Tissue printing revealed that ABA inhibited most of the EBM activity in the endosperm cap, but not in the remainder of the endosperm. ABA did not inhibit cellulase activity. There was a transient rise in ABA content in the embryo during imbibition, which was likely to be responsible for slow germination, suggesting that endogenous ABA also may control embryo growth potential and the second step of endosperm cap weakening during coffee seed germination

Exogenous gibberellins inhibit coffee (Coffea arabica cv. Rubi) seed germination and cause cell death in the embryo

The mechanism of inhibition of coffee (Coffea arabica cv. Rubi) seed germination by exogenous gibberellins (GAs) and the requirement of germination for endogenous GA were studied. Exogenous GA4+7 inhibited coffee seed germination. The response to GA4+7 showed two sensitivity thresholds: a lower one between 0 and 1 µM and a higher one between 10 and 100 µM. However, radicle protrusion in coffee seed depended on the de novo synthesis of GAs. Endogenous GAs were required for embryo cell elongation and endosperm cap weakening. Incubation of coffee seed in exogenous GA4+7 led to loss of embryo viability and dead cells were observed by low temperature scanning microscopy only when the endosperm was surrounding the embryo. The results described here indicate that the inhibition of germination by exogenous GAs is caused by factors that are released from the endosperm during or after its weakening, causing cell death in the embryo and leading to inhibition of radicle protrusion