Hi Valentino,

I do not know about specific malus or even Rosaceae literature on day/night leaf growth rate, but have you read these ones ?

Somewhat related papers on malus growth you might find interesting : 

I hope this would help. And I would also be very interested in finding papers or results on night/day leaf growth rate for apple!

Have a nice day,

Hi. Yes it makes sense to think that plants may invest more in leaf growth when they are not subjected to water stresses, i.e. at night. However, Arabidopsis leaves were found to grow more during the day (http://onlinelibrary.wiley.com/doi/10.1111/j.1469-8137.2007.02053.x/epdf).

According to this great review (http://jxb.oxfordjournals.org/content/early/2012/01/05/jxb.err334.full.pdf+html), there is no common behaviour.. "In Helianthus annuus (Boyer, 1968) and Acer pseudoplatanus (Taylor and Davies, 1985), maximal leaf

growth rates were reported at night, in Phaseolus vulgaris (Davies and Van Volkenburgh, 1983) and Vitis vinifera (Shackel et al., 1987) maximal growth was reported during the day, and in Solanum lycopersicum the highest growth rates were found at the day–night transition (Price et al., 2001).

I just hope to find similar reports regarding Rosaceae..

This is not a simple question.  Apart from species-specific effects (see above), I suggest you consider how you define and measure  'growth'. If you mean cell division, then it is driven by circadian cycles (so it is at night). If dry biomass, then it is when photosynthesis occurs (although assimilate may be stored away from the site of synthesis and used in later leaf growth, there are source-sink relationships to consider, and there may be further circadian effects). If wet biomass, then it is when turgor pressure is greatest (normally at night). In apples, the seasonal dynamics of assimilate storage and re-mobilization are important, so obviously leaf weight may decline whilst fruit is  'growing'. 

Hi. This qestion is simple and is not simple.

1.The growth of plant bind with hormones level and its interaction. Some hormones synthesized better in dark (for example IAA) or some hormones in the light. Some hormones are rapidly destroyed in the light. As a consequence of the effect of auxin is manifested in the dark more.

Prof. Cornish correctly noted "If wet biomass, then it is when turgor pressure is greatest (normally at night). In apples, the seasonal dynamics of assimilate storage and re-mobilization are important, so obviously leaf weight may decline whilst fruit is  'growing'."

If you measured length of plants, you will see that grow at night. But under these conditions the dry weight of the plant will be reduced.

But if you measure the dry weight of the plant,  you will see that plant drowth at light.

Dear Prof. Cornish,

With leaf growth I simply mean the increase in leaf surface, so it should be driven by cell division and expansion. I'm not considering leaf biomass, neither wet nor dry. I'm quite aware of the seasonal dynamics of assimilate storage and re-mobilization, since it is important for apple production. 

My focus is on the VOCs related to leaf growth, so I must know when the leaf are growing most.

You also wrote "If you mean cell division, then it is driven by circadian cycles (so it is at night)". Could you please give me some advice about journals where I can find related literature?

Best regards,

Valentino

Under ideal situation (with no external stress factor)...I think, they grow faster in night than day time..as partitioning of energy for growth related activity is better during night time...!!

Still, Arabidopsis leaves were found to grow more during the day (http://onlinelibrary.wiley.com/doi/10.1111/j.1469-8137.2007.02053.x/epdf), under ideal, non-stress situation.