No abstract

Plants are sessile organisms that must perceive and respond to various environmental constraints throughout their life cycle. Among these constraints, drought stress has become the main limiting factor to crop production around the world. Water deprivation is perceived primarily by the roots, which efficiently signal the shoot to trigger drought responses in order to maximize a plant's ability to survive. In this study, the tomato (Solanum lycopersicum L.) mutant procera (pro), with a constitutive response to gibberellin (GA), and its near isogenic line cv. Micro-Tom (MT), were used in reciprocal grafting under well-watered and water stress conditions to evaluate the role of GA signaling in root-to-shoot communication during drought stress. Growth, oxidative stress, gene expression, water relations and hormonal content were measured in order to provide insights into GA-mediated adjustments to water stress. All graft combinations with pro (i.e. pro/pro, MT/pro and pro/MT) prevented the reduction of growth under stress conditions without a reduction in oxidative stress. The increase of oxidative stress was followed by upregulation of SlDREB2, a drought-tolerance related gene, in all drought-stressed plants. Scions harboring the pro mutation tended to increase the abscisic acid (ABA) content, independent of the rootstock. Moreover, the GA sensitivity of the rootstock modulated stomatal conductance and water use efficiency under drought stress, indicating GA and ABA crosstalk in the adjustment of growth and water economy.

RESUMO:Tithonia diversifolia, conhecida como girassol mexicano apresenta alto potencial de utilização no Brasil, em função de sua a adaptação às condições de baixa fertilidade do solo, dos diversos tipos de uso e de seu elevado valor nutricional. Objetivou-se avaliar a produção de biomassa e o valor nutricional de Tithonia, em função de espaçamentos e estádios de desenvolvimento das plantas. Conduziu-se o experimento em Marília-SP em delineamento blocos casualizados, em esquema fatorial 3 x 3, em três repetições. Os tratamentos foram os espaçamentos E1: 0,50 x 0,75 m, E2: 0,75 x 0,75 m e E3: 1,0 x 0,75 m e os estádios de desenvolvimento das plantas (pré-floração, floração e pós-floração). A produção de biomassa fresca no menor espaçamento foi superior aos demais somente na pós-floração, já a produção de biomassa seca na pós-floração não apresentou diferenças entre E1 e E2, porém nestes a produção foi superior ao E3. Para os teores de PB, EE, FB, MM, celulose e lignina, a interação entre os tratamentos não foi significativa. Os espaçamentos não afetaram o teor de PB, porém na pré e pós-floração os valores foram superiores ao da floração. Para os teores de FB, MM e celulose ocorreram diferenças entre espaçamentos e estádios da planta e para a lignina, somente para estádios da planta. Para os teores de FDN e FDA ocorreu interação significativa entre os tratamentos. O menor teor de FDN foi obtido no E1 e na pré-floração, porém não diferiu estatisticamente do E2 e do estádio floração. Para o teor de FDA, os melhores resultados foram obtidos nos espaçamentos E2 e E3 e na pré-floração. Baseado na produção de biomassa e na análise bromatológica, conclui-se que principalmente no menor espaçamento e na pré-floração que o uso de Tithonia é uma alternativa promissora como suplementação protéica na alimentação animal.Palavras-chave: Tithonia diversifolia. Forrageira arbustiva. Produção de biomassa. Valor nutricional. Fresh biomass yield in the smallest spacing was superior to the others only in post-flowering stadium. In other way, dry biomass yield in the post flowering, didn't present differences between E1 and E2, even so in these situations, yield was superior to E3. For PB, EE, FB, MM, cellulose and lignin content, the interaction between treatments was not significant. Spacings didn't affect PB content, however in pre and post-flowering the values were superiors to those ones obtained from flowering stadium. For FB, MM and cellulose contents, significant differences were observed between spacings plant development stadiums and for INFLUENCE OF SPACING AND PLANT DEVELOPMENT STADIUM IN BIOMASS YIELD AND NUTRITIONAL VALUE OF

Since the influence of the rootstock on the scion and vice versa was noticed, a number of experiments have been performed in an attempt to establish the basis of the transport of molecules and signals between both parties (see review Aloni and others 2010; Martínez-Ballesta and others 2010). In these experiments, grafting has been an important tool in biological research for discovering how long-distance communication can coordinate and modify plant development in response to endogenous and environmental factors. For instance, when growing fruit, it is common to use rootstocks that induce a dwarfed size of the scion. This reduction of Abstract Grafting has been a long-standing technique used to improve crop production and provide tolerance to biotic stresses, including soil-borne pathogens, as well as tolerance to abiotic stresses, such as cold, salinity, drought, and heavy metals. Currently, beyond its use in horticultural production, grafting has received great prominence as an important research tool, mainly regarding signaling mechanisms related to root-shoot communication. Most of the emphasis from recent studies has been on detection of the long-distance transport of molecules and signaling factors, especially phytohormones, RNAs, peptides, and proteins. Through these studies, there have been significant breakthroughs about the underlying mechanisms implicated in the regulation of developmental and stress responses at the whole plant level. Because of this, the aim of this paper is to provide an overview of grafting as an important tool for plant science. Thus, in the following sections, we will summarize what is most recent and relevant in the use of grafting in plant research.

The okra (Abelmoschus esculentus L. Moench) is one of the most important vegetables in the world and is a popular food item in many tropical and subtropical countries. Besides its cultivation for fresh consumption, okra also has potential industrial uses. Nonetheless, pests and diseases remain the most damaging factors affecting its crop yield. Among these, root-knot nematodes are the main pests limiting okra production. This study aimed to determine the responses of plant species of the Malvaceae family to Meloidogyne incognita and M. enterolobii rootknot nematodes, and to also assess the compatibility of the same with the okra commercial 'Colhe Bem IAC'. Resistance was evaluated using the reproduction factor in two commercial okra cultivars ('Colhe Bem IAC' and 'Santa Cruz 47'), five cotton (Gossypium hirsutum L.) plant genotypes (PRO 277, IAC 29-233, PR 136, IAC 24, and IAC 03-979), and vinagreira (Hibiscus sabdariffa L.) Other resistance-related traits measured were the percentage of healing, plant height, root length, rootstock stem diameter, scion stem diameter, number of leaves, total fresh weight, and fresh weight of the scion, rootstock, and root parts. While the cotton and vinagreira genotypes tested were resistant to both species of nematodes, okra cultivars were not. The okra, however, showed successful adaptation to grafting, which may offer an important physical resistance against attacks by root-knot nematodes, while vinagreira showed the greatest potential for use as rootstock for protecting okra crops.