hello,

this may be because the increase of the total solids during the storage period.

a little dehydration of water is happening during storage and this increase the total solids , subsequently the tocopherols.

Ebrahim's response is certainly one possible mechanism. At what point are the tocopherol measurements being taken and is there a corresponding loss of H20?  

There are other possible explanations.  Does your reference or work directly link storage, stress, and  increasing tocopherol content? A second fairly plausible explanation would be that Tocopherols (some if not all) are fairly effective antioxidants.  This is the reason tocopherols are often added to processed foods and supplements, they ( especially as a-tocopherol) prevent the oxidation of the product they are added to.  If the increase is not correlated to water loss over time it is likely the increase is seen due to the plant increasing its endogenous production of tocopherols to limit oxidative stress. 

You want to tear romaine lettuce the day before you eat it because it releases a substance that is beneficial for humans. My theory for your question is that since the vegetable is still alive and has been damaged, it is trying to protect itself.  Pyto-protection conveys to human protection  Robinson, J. (2013). Eating on the Wild Side: The Missing Link to Optimum Health (1 edition.). New York: Little, Brown and Company.

Thank you.

a-tocopherol (intended to be read as alpha-tocopherol) and other tocopherols are utilized by humans and other animals as a dietary source of Vitamin E.  Vitamin E (as with any other true vitamin ) has been determined to be required for human life.  Thus the intake would be beneficial.  The nutritional benefit of mechanically damaging vegetables prior to injestion to increase nutrition levels (e.g. Vitamin E) would likely be of dubious benefit.  While it might increase some nutrients such as tocopherols, it would likely reduce others such as Vitamin C.  The reason for this is the damage results in free radicals which cause oxidative stress and damage.  Vitamin C is likely to be seriously degraded due to its function as an antioxidant if the plant matter were damaged.  Also the associated free radicals would likely oxidise other components of the plant material, especially any which function as antioxidants.  Any remaining free radicals would also cause oxidative stress if consumed.  Overall the loss of Vitamin C and other oxidation prone molecules would probably be more detrimental to health then the slight increase of Vitamin E.  This is likely indicated by the preference for undamaged crisp vegetables over damaged oxidised fruits and vegetables.  A few exceptions to this would be fermented items such as non green tea's.