Table 1

		Production system
		Traditional Greenhouse	Mulch greenhouse	Open field
Lettuce head weight (g)*		373.8^A ± 96.7	388.7^A ± 70.8	352.0^B ± 59.1
Total leaf number*		20^A ± 1	23^A ± 1	34^B ± 2
Leaf area‡ (cm²)	External	306.6^Aa ± 47.7	323.0^Aa ± 41.7	238.8^Ba ± 55.0
	Middle	240.9^Ab ± 95.7	254.8^Ab ± 76.5	188.0^Bb ± 39.1
	Internal	42.7^Ac ± 12.3	116.5^Bc ± 14.6	80.2^Cc ± 16.8

* Zones were not defined; therefore only between production systems comparisons were performed. Different uppercase letters indicate significant differences between production systems (p<0.05)
‡Lsmean values are reported, different lowercase letters indicate significant difference between zones (p<0.05) and uppercase letters indicate significant differences between production systems (p<0.05)

Table 1: Mean values at harvest of vegetable growth parameters of lettuce heads produced under different systems.