Aeration stress in plant tissue cultures

Abstract

Summary.The requirement for sterility in plant tissue cultures avoidance of dehydration can impose sealing requirements that severely limit the rate of gas exchange in and out of the culture vessel. Conditions within the culture vessel such as the depth of any water cover, the presence of gelling agents, the bulk and porosity of the tissue and the temperature also strongly influence in vitro rates of gas exchange, primarily driven by diffusion. This article uses elements of Fick's Law of Diffusion to identify key factors limiting gas exchange between culture and its immediate surroundings. In particular, it identifies static liquid media, gelling agents, large tissue mass and warm temperatures as imposing severe limits on diffusive flux for gases such as O 2 , CO 2 and ethylene. The principle barrier to diffusive exchange of gases between the in vitro and ex vitro atmospheres is the wall of the enclosing vessel. This is invariably made of glass or plastic that is gas-impermeable and well-sealed against evaporative drying or entry of micro-organisms. Cultures enclosed in this way will, inevitably, asphyxiate unless a compensating pathway for diffusive gas exchange is contrived or replaced by some system of convective flow that carries gases to and from the tissue. Supplementing diffusive aeration with convective flow is the basis of most successful hydroponics systems for whole plants and may be a prerequisite for securing levels of aeration suitable for autotrophic cultures. The paramount consideration is the extent to which the total rate of consumption or production of a particular gas by the cultured tissues is matched by the maximum rates of gas transport imposed by the culture itself, its immediate surroundings and the ventilation and sealing system of the culture enclosure.

In vitro Growth of Dwarf Cavendish Banana Plantlets in Different Culture Vessels and Light Intensities

“…Res., 11 (1): 23-31, 2016 cotton plants in vitro under low light intensities. Jackson et al (1987) and Miller and Murashige (1976) have also reported of high biomass production of Dracaena plants in vitro under 10,000 Lux which is twice as much as the 5000 Lux optimum reported in this work. High light intensity results in increase in total number of leaves, dry matter, sugar content and nitrogen absorbed in plants while excess light causes stunting of stem and leaf (Soontornchainaksaeng et al, 2001).…”

Aspectos morfofisiológicos na pré-aclimatização in vitro e aclimatização de plantas de caroá

“…Em vista disso vários estudos e trabalhos vêm sendo desenvolvidos com o intuito de minimizar os danos causados pela transição de uma condição à outra (CHANDRA et al, 2010;JACKSON, 2003). Souza et al (2006) sugerem a pré-adaptação à condição autotrófica mediante redução da concentração de sacarose no meio de cultura, para promover a rustificação in vitro, buscando aumentar a capacidade fotossintética das plantas.…”

“…Outro fator que merece destaque é a aeração dos recipientes de cultivo. A condição de esterilização necessária aos cultivos in vitro e a manutenção do ambiente asséptico no interior dos frascos de cultivo impõe um selamento severo dos recipientes, impedindo dessa forma trocas gasosas, tão necessárias ao bom desenvolvimento das plantas (JACKSON, 2003). Buscando minimizar essa ausência total de trocas gasosas, vários autores vêm trabalhando nesta direção considerando, principalmente, os recipientes a serem usados assim como a forma de vedação (SILVA et al, 2005).…”

Multiplication and growth of hybrid poplar(Populus alba × P. tremula)shoots on a hormone-free medium

“…The studies conducted on some flooding-resistant plant species (e.g., rumex palustris) revealed that strong enhancement of shoot elongation in these plants under submergence, although directly regulated by gibberellin, is enabled by plant-produced ethylene gas which is trapped and accumulated inside plant tissues due to the low rate of underwater diffusion, triggering a subsequent increase in gibberellin levels [1,28]. Considering that both the sealing of explants in small-volume culture vessels and the flooding experienced by plants in the outside world result in the similar restriction of gas exchange between the internal and external environments [13]. This model might provide one of the possible explanations for the increased shoot elongation which is followed after the culturing of explants in sealed culture tubes.…”