I don't know how the images are, but problably you can perform an "automatic threshold", then "analyze particles" and finally "Measure" the particles (leaf). It will lead you to the area of the leaf. I'm not familiar with the leaf area index...

Hope it works!

Hi Jayaramaiah,

A lot of work has been done on LAI (and hence LA) with hemispheric objectives on camera's in the field. This work dates back for more than 10 years now. Software (CANEYE) has also been developed and can be downloaded at:

http://www6.paca.inra.fr/can-eye

The most used and according to me also the most accurate software was developed by INRA (Institut National des Recherches Agronomiques or the French National Agricultural Research Institute). I have used this software myself in field work and also my students use the software in practical exercises in remote sensing. The method is one of the best to estimate LAI in forests but also agricultural plots or other types of vegetation, better than the LAI-2000, which is useless in forests. The LAI-2000 does not enable to discriminate between leaves and trunks for example. Crucial is that color has to be acquired by the camera when one wants to determine a LEAF area index.

If something would not be clear please let me know. The type of camera we used is a NIKON body equipped with a NIKON standard hemispheric objective. The best one, but not the cheapest one, especially the hemispheric objective is expensive.

The website I mentioned will give much more information than I can give here. Please do consult it for further detail on methodology, software and camera's. An international consortium VALERI (Validation of European Remote Sensing Satellites), uses the technique to perform intercomparisons of LAI in field campaigns worldwide, together with a NASA team.

Cheers,

Frank

Frank provided a great explanation for easy and accurate LAI measurement.

However, if you want discrete leaf area using imagej, you have to use a plane image of a leaf (using a flat scanner for example), knowing your image scale (you can draw a linear segment of 5 cm next to the leaf). 

Using the straight line tool you can outline the scale, then click Analyze > Set scale... This box will help you to tell imagej how long in cm your straight line is. Then you just have to threshold your image and do a particular analysis to know the area in cm2. I attach a small tutorial (in french language) I had made for interns, hope it helps!

Regards,

Alexandre

I know this an old thread and am not sure if you still need assistance, but I would defintely recommend you visit www.MIPAR.us.

It is very powerful and intuitive 2D/3D image analysis software written by scientists/end-users and is about to be released as a free trial on December 14th. You can sign up on the site as well as submit images/datasets to test.

There are many image analysis options available, but I think you may just find MIPAR to be something special if you give it a try!

A very simple ut accurate method is the following.

1) Take a photocopy of the leaf.

2) Take a photocopy  of a rectangle 100 cm² (10x10cm)

3) Weigh both the rectangle and the photocopy of the leaf after having cut out the shape of the leaf from the photocopy paper. Use a balance with an absolute accuracy (or 3 times ) of 1 mg.

4) Apply a rule of three on the weights of both the leaf and the 100 cm² paper photocopies.

5 The result of this rule application is the surface area of the leaf. The accuracy of the surface estimate is better than 5%, depending on how well you have cut out the leaf shape from the photocopy.

6) Apparatus needed? A photocopier and a balance with an accuracy (or 3 times ) of 1 mg. I would guess that these instruments are pretty standard in a lab. The cost is the cost of the photocopy paper and the use of the photocopier. Of course labour is a cost as well which may be taken into account.

7)  Complicated leaf shapes (ferns for example) give problems. But te method is very good for trees and crops. Deadly simple and very accurate, but not suitable for large amounts of leaf samples to be processed. In that case it's better to use dedicated software and photographs of leaves and standard (known) surface areas.

Cheers,

Frank