The use of silicon in Billbergia zebrina cultivation in vitro is an alternative for optimizing micropropagation of this important ornamental plant species. The objective of the present study was to evaluate the growth and anatomical and physiological alterations in Billbergia zebrina (Herbert) Lindley plants as a function of different sources and concentrations of silicon during in vitro cultivation and acclimatization. The experimental design was completely randomized, with a double factorial arrangement and an additional control treatment (2 x 3 + 1). The first factor was relative to calcium silicate and sodium silicate added to the Murashige & Skoog culture medium; the second factor was related to its concentrations, 0.5, 1.0, and 2.0 mg L-1. After 100 days, their growth, anatomical characteristics, level of silicon and chlorophyll content were evaluated. Growth characteristics were assessed after 60 days of acclimatization period. Plants absorbed more sodium silicate than calcium silicate. This source also stressed the plants impairing their growth, but the highest silicon absorption at 1 mg L-1 attenuated the stressful conditions. The supplementation of the culture medium with calcium silicate led to improved growth, anatomical, and physiological characteristics, which benefited the development of more resistant seedlings with better performance during acclimatization.

No abstract

Conditions of water deficit can cause morphological changes in plants which consequently affect physiological processes and interfere with plant metabolism. As grafting is a standard process used for citrus trees, these changes depend on the rootstock used and its interaction with the scion; this interaction will determine which plant has the best performance. This study involved assessment of changes in DNA and chlorophyll A and B content in Navelate orange seedlings grafted onto five different rootstocks (Indian and San Diego citrandarin, Swingle citrumelo, Santa Cruz Rangpur lime and Sunki mandarin) under conditions of water deficit. The seedlings from the respective combinations were approximately 12 months-old when they were transferred to 5 L polyethylene bags filled with substrate, comprising standard soil and sand at a 3:1 ratio. Plants were maintained in a greenhouse for three months. After this period, the experiment was set up using a randomized block design with a 5x2x5 factorial scheme based on the following: five rootstocks with and without irrigation, and time-points at 25, 29, 32, 35 and 38 d after stopping irrigation. At each of these time-points, chlorophyll content was assessed by direct reading in cloroLOG CFL1030 equipment and also the DNA content was determined using flow cytometry. The results suggest that severe water deficit can cause morphological changes in DNA content and in chlorophyll concentration, and that the changes are most marked with Sand Diego and Swingle rootstocks. Index terms: flow cytometry, chlorophyll content. Respostas morfológicas da laranjeira Navelate enxertada em diferentes porta-enxertos e sob déficit hídrico RESUMOAs condições de déficit hídrico podem causar alterações morfológicas em plantas que consequentemente afetam os processos fisiológicos e interferem em seu metabolismo. Essas mudanças dependem do porta-enxerto usado e sua relação com a copa uma vez que a enxertia é um processo padrão usado na formação das plantas cítricas. Este estudo teve como objetivo identificar o melhor desempenho da interação de diferentes porta-enxertos com a copa Navelate em condições de estresse hídrico; mediante avaliação do conteúdo de DNA e clorofila A e B. Foram estudados os portaenxertos citrandarin Indio e San Diego, citrumelo Swingle, limão Cravo Santa Cruz e tangerina Sunki

No abstract

Psorosis is a very well known citrus disease causing important damage in many countries, in particular in Argentina and Uruguay. Based on reports of symptoms such as bark scaling on trunks and branches observed on orange, mandarin and grapefruit trees, this disease was also present in Cuba. To determine the presence of the virus, 32 samples from trees with psorosis symptoms were collected from the Cítricos Ceiba, Victoria de Girón, Cítricos Sola and Cítricos Ciego enterprises. These samples were analyzed by TAS-ELISA. Four samples, which tested positive for psorosis, were also positive when evaluated by hemi-nested-PCR, electron microscopy and biological indexing on Madame Vinous and Pineapple sweet orange. The four isolates induced symptoms of chlorotic flecking in young leaves of citrus indicator plants and characteristic filamentous viral particles were observed by electron microscopy.