Plant Growth Chambers for Tissue Culture

The Foundation of Tissue Culture

Plants possess a unique process known as totipotency which is the ability of plant cells, tissues or organs to differentiate into a complete and fertile individual. The concept of totipotency was first put forward in 1902 by the German scientist, Gottlieb Haberlandt, who is considered to be the ‘father of plant tissue culture’. The development and improvement of tissue culture techniques were a focus from the 1940s to the 1960s and together with recent nutrient modifications are still used today. During the 1970s and 1980s tissue culture expanded its application from research to commercial agriculture, horticulture and forestry [1].

The fundamental areas where tissue culture is applied are cell behavior, plant breeding, crop improvement, germplasm storage, clonal propagation, the evaluation of nutritional phytochemicals, resistance to biotic and abiotic stresses and commercial industrial products [2]. Although initially used as a research tool, tissue culture is used to rapidly propagate commercially grown disease free plants including bananas, pineapple, wheat, rice, orchids, spices, coffee, sugar cane, pine, strawberries, raspberries as well as other fruits, ornamentals, forestry plants and medicinal plants [2,3].

Tissue Culture Vessels & Microclimate Requirements

Tissue culture vessels act as a miniature greenhouses or small growth chambers, and the environment should be sterile and kept under strict environmental control [4]. The most efficient way to adjust the vessel microclimate is to control the external environment such as in a controlled environment growth chamber.

The tissue culture vessels with their caps are at the interface of the external and internal environments. Seven tissue culture vessels were evaluated and the results indicated that the round vessels had more uniform light distribution and the material used impacted the spectral distribution reaching the callus and plantlets [5]. Polypropylene materials transmit wavelengths between 360 and 760 nm while polycarbonate vessels cut out UV which can induce formaldehyde production and degrade the iron, nitrate and the phytohormone indole-3-acetic acid concentrations in the selected growth media [5,6]. It is therefore recommended that light between 290 to 450 nm be reduced either through use of polycarbonate vessels, a yellow long pass filter or lamp selection.

Another important physical characteristic is the air exchange rate defined as the hourly volumetric ventilation rate divided by the air volume in the vessel [4]. Adequate air exchange is important to improve stomatal function, photosynthesis, and growth of the plantlet with an optimum of 4.4 air exchanges per hour [7]. In general, the optimum temperature in the culture vessel is 25°C for C3 plants and often higher for Crassulacean Acid Metabolism (CAM) plants [8,9]. High relative humidities inside culture vessels can be observed particularly when the air exchange rate is low. In the plum species Prunus cerasifera, shoot and root proliferation and growth decreased when relative humidity in the vessel fell below 80-90% however higher relative humidities resulted in poor plantlet survival rates during acclimation [10].

Light – The New Frontier for Plant Tissue Culture Optimization

Plant tissue cultures require light primarily to regulate photosynthesis, morphogenesis and metabolism with photoperiod, intensity and spectral distribution all playing a role [11]. Before the advent of LEDs, cool white fluorescent and sometimes high pressure sodium lamps were used. Today LEDs are used and can be adjusted to optimize the spectrum for the different stages of tissue culture such as callus induction, proliferation, shoot and root formation, acclimation and sometimes flowering [12]. Photoperiod requirements are species specific with some explants needing total darkness or continuous light for shoot and root formation, however the majority of plants need photoperiods between 8 and 18 hours per day [11]. All stages of tissue culture do well at low light under 100 μmol/m2/s.

Spectrum plays a role in callus formation and proliferation, it has been shown that red, blue and yellow light improved callus induction, differentiation and proliferation in many species [12,13]. Shoot induction, proliferation and growth was positively impacted when exposed to blue and yellow light and repressive effects were observed under red or green light. A combination of red, blue and green light increased root induction and growth [12]. The recommended spectrum was concluded to be a balanced, broad-spectrum light regime using a tunable light that could be adjusted for the various stages of plantlet growth and development. Another more recent study was performed to find an optimal spectrum that would support all stages of tissue culture for the production of disease-free European chestnut plantlets which are typically difficult to micropropagate [14]. Warm white, red and blue (RB), red, blue and far-red (RBFR), red, blue, green and far-red (RBGFR) LEDs, and fluorescent lamps were evaluated on shoot and root formation, stomatal characteristics, physiology and morphology of plantlets. In summary, RB light was suboptimal while RBFR and RBGFR had the highest success rates [14]. It was suggested that this was due to the 10% FR in these spectra. Far-red light alone has been shown to inhibit root formation [15].

Common Research Topics

Common plant science research applications of tissue culture include:

• Large-scale clonal propagation of elite plant material
• Production of genetically uniform experimental plant populations
• Generation of disease-free plants
• Germplasm conservation and longterm genetic resource preservation
• Rescue and propagation of rare, endangered, or difficult-to-grow species
• Accelerated breeding and rapid multiplication of new cultivars
• Study of plant developmental biology
• Screening for abiotic stress tolerance
• Screening for biotic stress interactions
• Preconditioning plant material for greenhouse or CEA deployment
• Uniform starter plant production for vertical farming and indoor agriculture
• Validation of controlled-environment growth protocols before scale-up

Recommended Plant Growth Chambers

Plant tissue culture research typically relies on multi-tier reach-in chambers or walk-in growth rooms designed for low light, high uniformity, and condensation-controlled airflow - with the choice driven primarily by scale and workflow, not light intensity. Regardless of form factor, tissue culture research chambers should prioritize:

• Low to moderate light intensity rather than maximum output
• Excellent air distribution to reduce condensation and contamination risk
• High spatial uniformity (temperature and light between shelves)
• High shelving density to maximize cultures per square meter
• Reliable environmental repeatability across experiments

Below is a simple decision guide:

• Small lab / method development: Multi-tier reach-in chamber
• Core research facility: Tissue-culture-configured reach-in chambers
• Large propagation programs: Walk-in tissue culture rooms
• CEA integration: Small multi-tier reach in or custom tissue culture growth rooms depending on the scale required

Recommended Conviron Chambers

GEN1000 & 2000:
• Primary reach-in chambers used for tissue culture and micropropagation
• Multi-tier configurations maximize vessel density
• Engineered options for upward airflow minimizes condensation in jars and petri dishes
• Low to moderate LED light intensities appropriate for in vitro growth
• The GEN2000 is a larger-capacity reach-in chamber for higher-throughput tissue culture research

Conviron Stratos Series Walk-In Tissue Culture Rooms:
• Purpose built, walk-in tissue culture room
• Modular platform that can be easily scaled to match high throughput requirements
• Pressurized plenums deliver uniform vertical airflow at each shelf to minimize condensation in jars and petri dishes