Agriculture Reference
In-Depth Information
9.3.9 SPECIFIC LEAF AREA (SLA)
It is a sign of leaf thickness, and usually decreased under drought stress
(Marcelis et al., 1998). Decreasing pattern of SLA under drought situation
is due to the different sensitivity of photosynthesis and leaf area expansion
to soil drying. Research has indicated that WUE of a crop is related to the
morphological characteristics of leaves. Wright et al. (1994) proposed that
under field conditions at moderate temperatures there is a close negative
correlation between WUE and SLA. Moisture stress affects leaf expansion
earlier than photosynthesis (Jensen et al., 1996; Tardieu et al., 1999). Re-
duction of SLA is believed to be a mode to improve WUE (Craufurd et al.,
1999; Wright et al., 1994). This is due to thicker leaves generally having
a higher density of chlorophyll and proteins per unit leaf area and, thus,
have a greater photosynthetic capability than thinner leaves. This correla-
tion ship between WUE and SLA may be due to the reality that plants with
low SLA (thicker leaves) have high nitrogen content and more mesophyll
cells per unit area, both leading to higher rates of CO
2
assimilation, and
consequently, higher biomass production (Thumma et al., 2001). Drought
stress, that reduces SLA, may also raise WUE in leaves. This is possibly a
part of an adaptive mechanism for reducing leaf area and transpiration rate
(Craufurd et al., 1999).
9.4 CONCLUSION
The environmental uncertainties especially drought stress faced by crop,
therefore, the primary objective will be to optimize confined management
practices to reduce severe stress as far as possible and, in particular, to
intensify the search for important physiological traits such as osmotic ad-
justment, CMS, photosynthetic and transpiration rate, stomatal conduc-
tance, WUE, chlorophyll fluorescence parameters, photosynthetic pig-
ment content, plant canopy temperature simultaneously with biochemical
attributes including level of antioxidant enzymes, nonenzymatic antioxi-
dant and pyridine nucleotides involve in drought tolerance mechanism in
respect of climate change scenario.
