As a function of PPFD
, the net assimilation rate of C[O.sub.2] (A), stomatal conductance (gs), internal C[O.sub.2] concentration (Ci) and leaf transpiration rate (E) were determined according to (ZHANG et al., 2001), where WUE corresponds to the efficiency of water use, iWUE is the intrinsic efficiency of water use and Fc is the carboxylation efficiency.
Measurements were taken with the Li-6400 photosynthesis system at ten light levels: 2000, 1400, 1000, 600, 400, 200, 100, 50, 20, and 0 [micro]mol x [m.sup.-2] x [s.sup.-1] photosynthetic photon flux densities (PPFDs
The direct sunlight photosynthetic photon flux density (PPFD
) was 2121.
Plants cultured at different PPFD
demonstrate morphological, photosynthetic and metabolic differences (Dai et al., 2009).
fue registrada con un sensor LI-190SA conectado a un datalogger (LI-COR LI-1000, Lincoln, EUA).
Light intensity was maintained at photosynthetic photon flux density (PPFD
) of 20 u mol m-2 s-1 provided by cool white fluorescent lamps.
To measure the basal rate of isoprenoid emissions, all gas exchange measurements were made in ambient [CO2] (380 M M-1), at PPFD
(photosynthetic photon flux density) of 1000 uM m-2 s-1, relative humidity of 50-55% and leaf temperature of 30C.
Net photosynthesis ([P.sub.N], [micro]mol [m.sup.-2][s.sup.-1]), stomatal conductance ([g.sub.s], mol [m.sup.-2][s.sup.-1]), leaf transpiration (E, mmol [m.sup.-2][s.sup.-1]), photosynthetic photon flux density (PPFD
, |mol [m.sup.-2][s.sup.-1]) and leaf temperature ([T.sub.1], [degrees]C) were measured from 10:00h to 12:00h under natural conditions on cloud-free days (PPFD
[greater than or equal to] 1600 [micro]mol [m.sup.-2] [s.sup.-1]) to ensure that maximum [P.sub.N] rates were measured.
In this environment, the photosynthetic photon flux density (PPFD
) near the leaves of N.
aurea attempts to increase its photosynthetic efficiency under low light intensity (e.g., in 50% shade), but when it is transferred into full sunlight, the combination of high PPFD
and temperature may damage PSII in leaves of this species, as has been shown in L.
Mean leaf temperature was 20.8 [+ or -] 1.3[degrees]C and mean photosynthetic photon flux density under greenhouse (PPFD
) was 388 [+ or -] 72 [micro]mol x [m.sup.-2] x [s.sup.-1].
The plants were repotted with around 2-3 plants per pot and allowed to acclimatize for four weeks in the plant physiology house at the National Institute of Education, Singapore, with a maximal photosynthetic photon flux density (PPFD
) of 700 to 800 [micro]mol[m.sup.-2] [s.sup.-1] and a daily temperature which ranged from 24[degrees]C to 33[degrees]C.