How can you increase the leaf size on fast plants? How can you increase the number of leaves a plant will grow?
There is no simple answer to these questions. The number of leaves on a plant is fixed mainly by the genetics of the plant which controls the arrangement of leaves on the stem. Of course, a bigger plant has more leaves, but it is not a simple matter to switch growth into extra leaf mass. Plants growing in drought conditions do DECREASE the area of their leaves (the leaves actually shrink). Therefore, to eliminate any stresses on the plants would encourage leaf growth. For Fast Plants, we would advise growth under a light bank with height of the plants adjusted daily to keep the leaves as close to the light bulbs as possible, watering via a wick system, minerals supplied through slow release fertilizers etc.
Plants are constantly balancing the amount of growth they put into shoots as against roots.
One feature that affects this is whether the plant is growing near other green plants. If a plant finds itself in competition with others, it will direct growth into leaf growth and away from reproductive growth (flowers, fruits, tubers or other storage organs). The plant can detect the presence of other plants within a metre of it by the spectrum of the light landing on its leaves. When its near neighbours are further away, it can afford to put more of its resources into reproduction.
There is a tool used by agronomists to explore how much leaf a crop produces. The Leaf Area Index (LAI) is the ratio of leaf area (one surface only) of a crop to the ground area upon which that crop stands. LAI values of up to 8 are common for many mature crops depending on species and planting density. Forest trees have LAI values of about 12 and many shaded leaves receive less than 1% of full sunlight.