Hi!

In fact the solid media that made with Agar Agar is porous itself/delicate nothing to worry. Only thing is constituents and the ex-plant that you select/use matters for growth. Hope you are using the correct constituents along with correct pH. pH value matters a lot for up taking the ingredients. Check thoroughly and do the experiment you get wonderful results. May I know what ex-plant are you working!!! 

Plant Tissue Culture Media: Types, Constituents, Preparation and Selection

http://www.biologydiscussion.com/plants/plant-tissue-culture/plant-tissue-culture-media-types-constituents-preparation-and-selection/10656

PLANT TISSUE CULTURE MEDIA

https://www.duchefa-biochemie.com/product/category/id/16

Good Luck!

Ms Ramadevi is correct; agar is already porous, although there is also room for improvement. 

However, to my understanding, the slow growth in culture is likely due to a combination of low CO2 and high humidity limiting growth. If you search "forced ventilation" you will come upon many papers that explore this and find that CO2 accumulates over night and crashes in the morning. Also, the high humidity can limit nutrient uptake by reducing the efficiency of transpiration. Finding a way to inject CO2 will achieve both these results and I predict will have a larger effect that increasing the porosity of the medium will alone.

This has more or an effect on larger chlorophilic cultures. Meristematic tissue and embryos lacking chlorophyll and stoma will not benefit in the same way. Also, increasing the porosity of media has shown to increase the root dry mass, but this was a radical change, such as vermiculite and under photoautotrophic conditions, which is another ball of wax entirely, and likely outside the scope of your question. But it is something to think about if the speed of growth is your primary concern. Search "photoautotrophic micropropagation" for more on that.

Hope that helps!

Hi,

I agree that agar is also porous though it is much less room for oxygen than other supporting materials, such as vermiculite or perlite. If the air movement inside the culture vessel increases, more oxygen will be provided to root system, which enhances root growth. This can't be solved with airtight vessels in conventional micropropagation. However, in photoautotrophic micropropagation, both natural ventilation with gas-permeable vessels or, especially, forced ventilation with direct air flush to the culture vessel, the increase in air current speed inside the vessel will increase the photosynthesis, transpiration of in vitro plants, and also gas diffusion of the supporting material.

you can try to replace agar to phytagel. best wishes.