Peltate trichomes in the dormant shoot apex of Metrodorea nigra, a Rutaceae species with rhythmic growth.

In Metrodorea nigra, a Rutaceae species with rhythmic growth, the shoot apex in the dormant stage is enclosed by modified stipules. The young organs are fully covered with peltate secretory trichomes, and these structures remain immersed in a hyaline exudate within a hood-shaped structure. Our study focused on the morpho-functional characterization of the peltate trichomes and cytological events associated with secretion. Shoot apices were collected during both dormant and active stages and processed for anatomical, cytochemical and ultrastructural studies. Trichomes initiate secretion early on, remain active throughout leaf development, but collapse as the leaves expand; at which time secretory cavities start differentiation in the mesophyll and secretion increases as the leaf reaches full expansion. The subcellular apparatus of the trichome head cells is consistent with hydrophilic and lipophilic secretion. Secretion involves two vesicle types: the smaller vesicles are PATAg-positive (periodic acid/thiocarbohydrazide/silver proteinate) for carbohydrates and the larger ones are PATAg-negative. In the first phase of secretory activity, the vesicles containing polysaccharides discharge their contents through exocytosis with the secretion accumulating beneath the cuticle, which detaches from the cell wall. Later, a massive discharge of lipophilic substances (lipids and terpenes/phenols) results in their accumulation between the wall and cuticle. Release of the secretions occurs throughout the cuticular microchannels. Continued protection of the leaves throughout shoot development is ensured by replacement of the collapsed secretory trichomes by oil-secreting cavities. Our findings provide new perspectives for understanding secretion regulation in shoot apices of woody species with rhythmic growth.

Characterization of Antixenosis in Soybean Genotypes to Bemisia tabaci (Hemiptera: Aleyrodidae) Biotype B.

Bemisia tabaci biotype B (Gennadius) is one of the most important soybean pest worldwide. Herein, 15 soybean genotypes were evaluated, to characterize the occurrence of antixenosis to B. tabaci biotype B. Initially, a multiple-choice test with all genotypes was carried out, evaluating the settling and oviposition preference at 3 d after infestation, and the colonization by nymphs after 48 d of infestation. Subsequently, a no-choice test, using 14 genotypes, was conducted with infested plants individually, and the number of eggs was counted after 72 h. Then, 10 genotypes were selected (indicative of resistance and susceptibility), which were evaluated for whitefly settling 24, 48, and 72 h after infestation and for oviposition 72 h after infestation. The trichomes of the leaflets were characterized for density, size, and inclination to establish possible correlations with the settling and oviposition in the genotypes. In the first multiple-choice test, involving 15 genotypes, 'IAC-17,' 'IAC-19,' and UX-2569-159 expressed antixenosis against B. tabaci. 'Jackson,' 'P98Y11,' and PI-229358 exhibited the same behavior in the no-choice test. In the multiple-choice test, 'Jackson,' 'P98Y11,' and 'TMG1176 RR' were the least attractive and least used for oviposition. The antixenosis shown by 'Jackson,' 'P98Y11,' and PI-229358 may be related to the characteristics of the trichomes (lower density and inclined). Based on the experiments carried out, 'IAC-17,' 'IAC-19,' 'Jackson,' 'P98Y11,' PI-229358, TMG1176 RR, and UX-2569-159 are considered promising for resistance to B. tabaci biotype B and may be exploited in soybean breeding programs for resistance to insects.

Estabelecimento in vitro e aclimatização de Lippia alba (Mill. ) N. E. Brown / In vitro establishment and acclimatization of Lippia alba (Mill. ) N. E. Brown

O presente trabalho teve por objetivo estabelecer in vitro a espécie Lippia alba (Mill.) N. E. Brown e promover a aclimatização de mudas dessa espécie. Para isso, foi testada a influência de diferentes concentrações e tempos de imersão em hipoclorito de sódio na assepsia dos explantes. Segmentos nodais foram imersos em hipoclorito de sódio nas concentrações 0,4; 0,6; 0,8 e 1,0 % e nos tempos 8, 12 e 16 minutos. Após 30 dias avaliou-se a contaminação bacteriana (%), número de brotos, número de folhas, e a taxa de sobrevivência (%). A concentração de 1% de hipoclorito de sódio foi a mais eficiente no controle da contaminação. Ápices caulinares de L. alba foram estabelecidos in vitro em meio MS suplementado com diferentes doses de BAP (0; 0,5; 1,0; 1,5 mg L-1). Após 140 dias avaliou-se a contaminação (%), a taxa de sobrevivência (%), a oxidação (%) e o número de brotos. Os melhores resultados foram obtidos para a dose 1,5 mg L-1 deste regulador. Para a aclimatização foram testados quatro tipos de substratos: pó de coco + calcário (1 g L-1), Plantmax® + calcário (1 g L-1), vermiculita + calcário (1 g L-1) e pó de coco + Plantmax® + vermiculita (1:1:1) + calcário (1 g L-1). Avaliou-se a taxa de sobrevivência (%), comprimento da parte aérea (cm), comprimento da raiz (cm), massa fresca da parte aérea e da raiz (g), e a massa seca da parte aérea e da raiz (g). Os melhores resultados foram obtidos quando com o substrato comercial Plantmax®.

The present study aimed to establish the species Lippia alba (Mill.) N. E. Brown in vitro and promote the acclimatization of the seedlings of this species. Therefore, we tested the effect of different concentrations and immersiog times in sodium hypochloritetfor the disinfection of explants. Nodal segments were immersed in sodium hypochlorite at the different concentrations of ,.4; ,.6; ,.8 and ,.0% during the different times of 8, 12 and 16 minutes. After 30 days, bacterial contamination (%), number of shoots, number of leaves and survival rate (%) were evaluated. The 1% concentration of sodium hypochlorite was more effective in controlling contamination. Shoot apices of L. alba were established in vitro on MS medium supplemented with different concentrations of BAP (;, ,.5; ,.0; ,.5 mg L-1). After 140 days, we evaluated the contamination (%), survival rate (%), oxidation (%) and number of shoots. The best results were obtained when we used the dose of ,.5 mg L-1 of this regulator. For acclimatization, we tested four types of substrates: coconut powder + lime (1 g L-1), Plantmax® + lime (1 g L-1), vermiculite + lime (1 g L-1) and coconut powder + Plantmax® + vermiculite (1:1:1) + lime (1 g L-1). We evaluated the survival rate (%), shoot length (cm), root length (cm), fresh weight of shoot and root (g) and dry weight of shoot and root (g). The best results were obtained when using the substrate Plantmax®.

The pulvinus endodermal cells and their relation to leaf movement in legumes of the Brazilian cerrado.

Legume pulvini have a clearly delimited endodermis, whose variable content has been associated with the velocity and type of leaf movement: pulvini in leaves with fast nastic movement contain starch grains; pulvini in leaves with slow nastic movements have calcium oxalate crystals as well as starch grains in the endodermis. However, the studies carried out to date have involved few legume species. This study therefore purported to examine the consistency of this hypothesis in other legumes. Thus, the structure and content of the pulvinus endodermal cells of nine legumes of the Brazilian cerrado, with different types and velocities of leaf movement, were investigated: slow nyctinastic and heliotropic movements ( BAUHINIA RUFA, COPAIFERA LANGSDORFFII, SENNA RUGOSA - Caesalpinioideae; ANDIRA HUMILIS and DALBERGIA MISCOLOBIUM - Faboideae; STRYPHNODENDRON POLYPHYLLUM - Mimosoideae), slow heliotropic movement ( ZORNIA DIPHYLLA - Faboideae), and fast seismonastic and slow nyctinastic and heliotropic movements ( MIMOSA RIXOSA and MIMOSA FLEXUOSA - Mimosoideae). Samples were prepared following standard plant anatomy and ultrastructure techniques. The endodermis of all the species contains starch grains. In the species displaying only slow movements, calcium oxalate prismatic crystals were observed in addition to starch grains, except in ZORNIA DIPHYLLA. In conclusion, oxalate crystals occur only in endodermal cells of pulvini that display slow movements, while starch grains are always present in pulvinus endodermal cells of plants with any kind of movement.