Some tomato plant leaves yellow due to a lack of sunlight on mature plants. When the plants become large, bushy, and heavy with fruit, the top portions of the plant can block the lower portions from getting sunlight.This can cause the leaves to yellow, and is really nothing to worry about.ou may need to also check your soil for a lack of nitrogen. Nitrogen will give a plant (everything from grass to vegetable plants) its dark green color, and good growth. A lack of nitrogen in the soil can cause the yellow leaves on tomatoes as well.
One example of phototropism is if you place a plant with sunlight to the right, than it will grow to the right where the sunlight is. Another example of phototropism is if you place a plant under something such as a table with sunlight shining above it, it will grow under and out in the sunlight.
The appearance of the signal results from a change that occurs in the rate of the primary processes of photosynthesis (electron flow and photophosphorylation) when there is a change in the intensity of light owing to the organismâs movement. Specialized phototaxis takes place by means of specialized structures. In the Euglena, such a structure consists of a paraflagellar body attached to the flagellum, and a colored stigma situated on the organismâs side. When in movement, whether in the dark or in light, the cell rotates around its longitudinal axis.