Neem secretory cells: developmental cytology and indications of cell autotoxicity.

The neem tree (Azadirachta indica A.Juss.) contains a range of biologically active compounds-mainly triterpenoids produced in single secretory cells, which are distributed among all plant parts. Neem secretions are toxic to animal cells, triggering autolytic mechanisms that culminate in cell disruption. However, little is known about the self-toxicity of these secretions to the cells that produce them. We carried out an anatomical, histochemical, and ultrastructural investigation of neem's single secretory cells in the shoot apex and in young leaves. We evaluated the morphological changes as possible evidences of stress reactions to their own secretions. The subcellular apparatus involved in synthesis and compartmentation was consistent with hydrophilic and lipophilic secretions. Polymorphic plastids devoid of thylakoids and abundant smooth endoplasmic reticulum in the later stages of differentiation are comparable with previous reports on neem cotyledons with regard to terpenoid synthesis. However, secretions were compartmentalized within autophagic vacuoles and periplasmic spaces instead of in terpenoid vesicles. Cellular swelling, increased vesiculation, dilatation of endoplasmic reticulum cisternae, mitochondrial hypertrophy in the cristolysis process, autolytic vacuoles, and vacuolar degeneration culminating in protoplast autolysis are all consistent with early indications of autotoxicity. The signaling stress reaction mechanism was expressed as cytoplasmic deposits of calcium salt and by the expression of a 70-kDa heat-shock protein. The morphological and histochemical changes in the secreting cells are comparable with those described in animal cells exposed to neem oil. Our data provide evidence of cell damage and signaling reactions linked to these cells' own secretions before autolysis.

Silica deposition and rate the nitrogen is silicon in rice / Deposição de sílica e teor de nitrogênio e silício em arroz

The nitrogen fertilization is an important practice to reach high productivity, however, nitrogen high level can cause lodging and make the plants more sensitive to disease. Numerous studies has demonstrate that a lot of grasses accumulate silicon at its tissues, and the biggest part of this element is deposited on the leaf, that would work like a mechanical barrier to diseases come in. However, high levels of nitrogen can reduce the silica deposition at the plants. The objective of this study was to evaluate silicon and nitrogen content in shoot and silica deposition in upland rice leaf as a result of Si and N levels. The experimental design used was completely randomized in factorial schema 3 x 2 with five replications. The treatments consisted from levels of N (5, 75 and 150 mg dm-3 of soil) in urea form and two levels of SiO2 (0 e 400 mg dm-3) in calcium silicate form (Wollastonita). The increased of urea fertilization reduced the silicon content of rice plants and the silica deposition at the external cells wall the epidermal rice leafs.

A adubação nitrogenada é pratica importante para alcançar altas produtividades, entretanto doses elevadas de nitrogênio podem causar tombamento e tornar as plantas mais suscetíveis a doenças. Numerosos estudos têm demonstrado que muitas gramíneas acumulam silício em seus tecidos, e que a maior parte deste elemento é depositado na folha, o que funcionária como uma barreira mecânica a entrada de doenças. Entretanto elevadas doses de nitrogênio podem diminuir a deposição de sílica nas plantas. O objetivo deste trabalho foi avaliar o teor de nitrogênio e silício na parte aérea, e a deposição de sílica em folhas de plantas de arroz de terras altas em função das doses de Si e N. O delineamento experimental utilizado foi inteiramente casualizado, em esquema fatorial 3 x 2, com cinco repetições. Os tratamentos foram constituídos por três doses de N (5, 75 e 150 mg dm-3 de N) tendo como fonte a uréia e duas doses de Si (0 e 400 mg dm-3 de SiO2) tendo como fonte o silicato de cálcio (Wollastonita). O incremento da adubação com uréia reduziu o teor de Si na planta de arroz e a deposição de sílica na parede externa das células da epiderme das folhas de arroz.

Silica deposition and rate the nitrogen is silicon in rice / Deposição de sílica e teor de nitrogênio e silício em arroz

The nitrogen fertilization is an important practice to reach high productivity, however, nitrogen high level can cause lodging and make the plants more sensitive to disease. Numerous studies has demonstrate that a lot of grasses accumulate silicon at its tissues, and the biggest part of this element is deposited on the leaf, that would work like a mechanical barrier to diseases come in. However, high levels of nitrogen can reduce the silica deposition at the plants. The objective of this study was to evaluate silicon and nitrogen content in shoot and silica deposition in upland rice leaf as a result of Si and N levels. The experimental design used was completely randomized in factorial schema 3 x 2 with five replications. The treatments consisted from levels of N (5, 75 and 150 mg dm-3 of soil) in urea form and two levels of SiO2 (0 e 400 mg dm-3) in calcium silicate form (Wollastonita). The increased of urea fertilization reduced the silicon content of rice plants and the silica deposition at the external cells wall the epidermal rice leafs.

A adubação nitrogenada é pratica importante para alcançar altas produtividades, entretanto doses elevadas de nitrogênio podem causar tombamento e tornar as plantas mais suscetíveis a doenças. Numerosos estudos têm demonstrado que muitas gramíneas acumulam silício em seus tecidos, e que a maior parte deste elemento é depositado na folha, o que funcionária como uma barreira mecânica a entrada de doenças. Entretanto elevadas doses de nitrogênio podem diminuir a deposição de sílica nas plantas. O objetivo deste trabalho foi avaliar o teor de nitrogênio e silício na parte aérea, e a deposição de sílica em folhas de plantas de arroz de terras altas em função das doses de Si e N. O delineamento experimental utilizado foi inteiramente casualizado, em esquema fatorial 3 x 2, com cinco repetições. Os tratamentos foram constituídos por três doses de N (5, 75 e 150 mg dm-3 de N) tendo como fonte a uréia e duas doses de Si (0 e 400 mg dm-3 de SiO2) tendo como fonte o silicato de cálcio (Wollastonita). O incremento da adubação com uréia reduziu o teor de Si na planta de arroz e a deposição de sílica na parede externa das células da epiderme das folhas de arroz.