Dear Mahar,

                      We used to store our plant extracts in 4 degree C, at that condition it will be stable up to 2 to 3 months, In case of fresh leave better to store at -20 degrees.

Simple logic in the freezer my mom used to keep the leaves and vegetables but , with in 10 days they spoil. 

So better to store under -20 or -80, for long time (Liquid nitrogen) 

Depending on the purpose of the storage. Liquid nitrogen is good for most cases. Not sure about -4 C. A good option is to make tests before and after the storage at -4 C and check statistics.

For better and trustworthy results you have to store leaves under deep freezing conditions (-80 C degrees), especially if you want to measure perishable compounds. Another option is to store at freezing conditions at first and then freeze dry the samples until analysis. It depends on how long you want to store the samples and what analyses you intend to do.  

it is not a long period just few day because i will bring them by plane ..and as you know it is forbidden to use liquid azote in plane

Dry ice, ask at biochemists special boxes with plenty of dry ice, but better to check.

thanks

Dry ice is a very good option but it's better to do this with a shipping company because otherwise it's a bit dangerous (dry ice might explode if not packaged properly and you do not that happen on a plane).

Dry ice and a sturdy Styrofoam box will do, also fix a good standard label (see below) outside the box for transporting.

Store -20 C of deep freeze dry for further studies

Deep freeze -20C is the best

Dry ice sounds like a good idea, but I would do some tests (time-course activity assays) in the lab prior to traveling with the samples. Some enzymes lose activity during storage even at -80C.

We have to think that always we have to make compromises when analysing plant tissues. It is impossible to analyse the samples immediately after harvest or cutting, because either you have a lot of samples or you have to transfer your samples, the methods are time consuming etc. There always will be some losses. You have to ensure that all the samples have the same treatment and of course you have to decide which compounds you can analyse according to your equipment.  

Freeze in liquid nitrogen immediately. Then  you have a chance to see the metabolic state which somehow represents the state of the leaf at the timepiont of its collection. 

When sampling we freeze fresh leaves in liquid nitrogen immediately in the field. Depending on what to analyse we use dark tubes for sampling, f.e. chlorophyll. Afterwards we store them at -80°C.

At the time I sample I put samples in liquid nitrogen. Righ after, samples are grinded and stored at -80. Biochemical assays are very sensitive, so little damage to samples might result in significant deviation. 

Only fresh leaf samples recommended for best test.