Water Use and Drought Response in Cultivated and Wild Apples - Abiotic Stress: Plant Responses and Applications in Agriculture - page 262

Perxoiredoxin Q

A

5

e d n

4.5

4

3.5

3

2.5

2

1.5

1

0.5

0

con drt

Treatment

B

Auxin-responsive protein

5

e d n

4.5

4

3.5

3

2.5

2

1.5

1

0.5

0

con drt

Treatment

Figure 4. Relative expression of leaf genes up-regulated by drought treatment. Experiments were conducted as de‐
scribed in Methods. Test transcripts were normalized against Actin. con: well watered controls; drt: treated to 40%
saturation for two weeks. A: relative expression of a peroxiredoxin gene; B: relative expression of an auxin-responsive/
ripening protein gene.

Leaf size and number have been shown to respond negatively to drought, resulting in longer
intervals between newly initiated leaves and smaller sizes, all features designed to reduce
transpiration to conserve water. Leaf morphological features and stomatal characteristics were
examined in the site 6 subpopulation [84]. GMAL3683.o had the smallest leaves by all traits
measured, whereas GMAL3687.d and GMAL3989.f had the largest leaves by area. Within the
GMAL3683 sibling group, GMAL3683.o leaf area (8.3 cm 2 ) clearly segregated from the other
three members (average = 20.3 cm 2 ).

Stomatal density has also been linked to drought tolerance and sensitivity. Therefore, we also
examined stomata size and density in the site 6 M. sieversii population. GMAL3691.m had the