Generally, there is variation of light availability and its quality in the nursery condition.
1) Many of nursery man grows that in backyard where a shady condition has arisen. How much will it affect its propagation efficiency, will it increase or decrease it?
2)Some times they use shade net of variable colour just to reduce the excessive light, however, using of different shade net, it will vary the light spectra. How will it effect its growth?
It depends on the plant you want to propagate. Some like shade anyway. And cuttings need too much light either until rooted and transferred into pots.
many of the references suggest thtat keeping the plants for few days in etiolated condition allows better rooting, especially the plants which are difficult to root. What is the physiology behind it?
Sounds surely not very scientific: but you cannot do both, that is growing roots from zero AND going on with photosynthesis. Roots normally grow in the dark and the leaves can do with less light too.
You may check out the following reference that suggests that the scion sticks were first etiolated for few days and then their cuttings were used. All show a similar story of better rooting incidence. Although many of such observations were recorded, I didn't find the detailed reason on why etiolated shoot is better in rooting.
These are some of the cases that has been cited for method of propagation by cuttings. I was expecting some other observations in other method of propagation like grafting or budding or layering, etc.
http://horttech.ashspublications.org/content/22/3/305.full
http://www.hort.cornell.edu/uhi/research/articles/IntPlantProp34.pdf
http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.505.126&rep=rep1&type=pdf
http://onlinelibrary.wiley.com/doi/10.1111/j.1469-8137.1978.tb01611.x/pdf
http://www.ncrs.fs.fed.us/pubs/ch/ch05/CHvolume05page228.pdf
http://www.actahort.org/books/455/455_65.htm
I did read the first one. In the beginning I did not realise that you work in a nursery that is with trees. With trees everything goes slowly.
I work with plantlets in tubes. I dont etiolate them. But nevertheless plants cannot do , as cutting, grow leaves and good roots. In sunlight. Need to be shaded.
It depends on and varies with plant species. Although minimal light is often required on the average.
Light not only improves photosynthetic activity but also harden the nursery plants to acclimatize and establish at new location with no mortality.
Suresh Sir, in nursery condition, we majority of the crops we used to keep it in shade avoiding the direct contact of the sunlight. Its true, light is responsible for photosynthesis, still we are using shade nets. Even now people are working with respect to colour of shade nets. Kindly share your views with respect to role of light intensity as well as light spectra from your experiences.
The term, hardening off, refers to the process of gradually exposing seedlings that have been raised in protective covering system to the climatic condition they will be grown in. The longer young seedlings remain in a controlled environment, the harder it is on them to adapt to the outside conditions. We introduce them gradually to the outside conditions as for other seedlings. Set the seedling containers outdoors in a lightly shaded, sheltered spot. Begin with just a few hours outside each day, and then gradually, over 3-4 days increase the time until the seedlings are there for more than half the day. By now the seedlings should be almost fully hardened, so keeping them well watered and still protected from the wind they can be brought out into the full sunlight. During the first day or so in full sun, if they start to wilt during the hottest part of the day, leave them there but give them some temporary shade. Comparatively seedlings raised in open light than shade are hard and establish with more vigour and grow speedly.
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