Plants make food during photosynthesis,and photosynthesis takes place mostly in plant leaves ,but when plant lose their leaves in the winter ,they do not die because leaves consumes a large part of food since the major metabolic activities happen there but rest of the tree is mainly dead tissue so it does not need food.In winters because of little sunlight and slow activities of enzymes it is very hard for plants to synthesise new food and thus in winter leafless tree has lesser food requirements and to meet them it has more than enough food.
