Effect of caffeine on grafted watermelon crop yields and fruit quality under greenhouse conditions

In watermelon crops in Southeastern Spain, important thermal differences appear during the first stages of plant development that can affect the crop. This work shows the effect of applying caffeine (plant growth inducer or growth reducer and it is connected with allelopathic effects including inter- and intraspecific effects), on yield and fruit quality parameters from a crop in a greenhouse in Southeastern Spain. We assessed two treatments of caffeine, T-1 (2.25 mu M), T-2 (9 mu M), and a control test using an experimental design of randomized blocks with four replications. Treatment did not affect the yield variables (p>0.05) kg m(-2), fruit m(-2) and kg/fruit, but there were significant differences (p <= 0.05) for rind thickness in the 2009 cycle. Results for soluble solids content, pH and flesh firmness did not show significant differences (p>0.05). The results showed that there is not any effect on the yield and fruit quality when applying the assessed treatments of caffeine.