Why horticultural products are more vulnerable to post-harvest losses?

Horticultural crops have high moisture content and due to their perishable nature they are inherently more liable to deteriorate especially under tropical conditions. They are biologically active and carry out transpiration, respiration, ripening and other biochemical activities which deteriorate the post-harvest quality of the horticultural commodities. 

As a result of respiration,  photosynthate which is stored in horticultural commodity (Fruits, vegetables & roots) are reduced. Due to respiration and transpiration heat and moisture is also accumulated in the horticultural commodity. This will leads to the deterioration of Fruits, vegetables & roots. 

Horticultural produce usually have short natural shelf life and storage period and they do not have protective structural or physical barriers. As an example, rice husk is act as a physical barrier. But in tomato they only contain soft and smooth bark. 

Usually fruits and vegetables have larger unit size compare to seeds. Therefore they are also susceptible to mechanical damages.