Effect of plant growth regulators on stomatal density, trichome density and phloem/xylem ratio in mango (Mangifera indica L.) 'Haden'.
Añez Q. M. E., Sergent A. E., Leal P. F.
Author Affiliation: Programa Producción Agricola Vegetal Universidad Ezequiel Zamora, UNELLEZ, Guanare 3310 Po., Venezuela.
Revista Unellez de Ciencia y Tecnología, Producción Agrícola 19 : 221-227
Abstract : In order to study the effect of paclobutrazol (PBZ) alone or combined with ammonium thiosulphate (ATS) or potassium thiosulphate (PTS), on stomatal density, trichomes density and phloem/xylem ratio in mango 'Haden', an experiment was conducted at Experimental Station Experta, UCV, Maracay, Aragua over two production cycles (1997-98 and 1998-99). The station situated at 10° 16?N and 67° 36? W, and at 450 masl. The experimental design used was completely randomized. The treatments were: To: check, T1: PBZ alone and the combination of PBZ plus ATS or PTS; the ATS and PTS at three different dosages and two different application time. The samples of leaves and internodes were collected yearly at the beginning of flowering. The results showed effect (P 0.05) in stomatal density with values from 803; 791; 760; 744 and 732 stomatas/ mm2 for ATS (1%) 90 d, ATS (0.5%) 90 d, PBZ, PTS (4%) 60 d and check, respectively, where most of the treatments with PTS were statistically smaller than PBZ alone and ATS treatments. The trichome density varied from 8 to 14 tricomes/mm2, there was effect (P0.05) among treatments, the higher values were: ATS (1%) 60 d with 13, ATS (0.5%) 60 d and 90 d with 12 and ATS (1%) 90 d with 12 trichomes/mm2. The lowest value was: ATS (2%) 90 d with 8, but this last treatment was the same (statistically) to the rest of the treatments. The PBZ showed positive effect for phloem/xylem ratio, although only three treatments: PTS (1%) 90 d with 1.05, ATS (0.5%) 60 d with 0.96 and PTS (2%) 90 d with 0.92, showed differences (P0.05) with respect to check, almost all treatments showed values about 1, being this value characteristic of medium or less vigorous cultivars, that condition will allow a more adequate agronomic management for 'Haden'.