There was a strong linear correlation between LMA and photosynthetic capacity, as estimated by Amax and Vmax, although there was no significant relationship between Amax and N content either base on leaf area or leaf mass (Figure 3).
In the present study, a negative linear relationship between LMA and Nm and a positive relationship between LMA and Amax were found in three Rhododendron species, but N content didn't show significantly correlation with photosynthetic capacity either base on leaf area or leaf mass (Figure 3).
We measured leaf number, rosette diameter, flower number and scored plant stress based on leaf colour.
Other non intrusive methods, such as those based on leaf dielectric constant [ 20] or those based on the water capacity to absorb terahertz frequency [ 21], are promising and certainly non-destructive but have low capacity to distinguish among different leaf areas or tissues.
The severity of the black rot symptoms were recorded based on infected leaf area, with the following disease indices: (0) less than 15%, (1) 15-30%, (2) 30-55%, (3) 55-75%, (4) more than 75% leaf area showing black rot symptoms.
In case of R. solani inoculation, disease ratings were visually graded into five classes based on the leaf area affected; 1 = no infection, 2 = 1 to 10%, 3 = 11 to 25%%, 4 = 26 to 50%, and 5 = more than 50% of leaf area affected.
Several studies on leaf area expansion of temperate angiosperms (Kozlowski and Clausen [1966]) suggest variations based on the type of shoots and the environment to which they are exposed (Kozlowski [1971]).
Thus, the leaf area ratio (LAR, leaf area per sample dry weight, mm mg−1) was not based on the total leaf area (Ryser and Lambers 1995) but on the leaf area of laminae, likewise the LAI (called LAI leaves from here on).
Disease on the third leaf was assessed at 14 days post inoculation, based on the percentage leaf area showing chlorosis.
