The burning process gives off carbon dioxide which plants take in as part of their growth. A carbon enriched atmosphere makes it easier for the plants to get the carbon they need. Some commercial growers flood their glasshouses with carbon dioxide.

Gk are these exam questions by any chance? They certainly sound like it to me... it isn't that we mind but if they are please could you say so.

my thoughts exactly mg. what level of exam too; that will affect how much detail is needed.

The two questions were from my 13 year old son's biology homework. He rang me today whilst I was at work and I looked on the net to see if I could find the answer which is how I came upon this forum. When I rang with the answer he told me he had already put down about carbon dioxide as it was in his notes. My son said the other question about the variegated geranium v normal plant was a bit harder but he should have known with the absence of chlorophyll. So thank you and next time I'll say if it is for his homework. My knowledge of gardening can be written on the back of a postage stamp with room for a poem or two. I do have some plants in the house, which I brought home from my mum's when she passed away last year (Mother's tongue and something with big leaves) I'll be looking for help soon. Thanks.

Gk glad we could be of help. The info was certainly more than enough for a 13 year old's homework.

Thanks