Ecofisiologia da germinação e crescimento inicial de Physocalymma scaberrimum Pohl (Lythraceae)

Abstract

Due to the lack of information about the germination process in most of the species that make up the Brazilian flora, mainly about native plants of the Cerrado. The objective of the present study was to evaluate the germination and initial growth of Physocalymma scaberrimum Pohl under the influence of light and temperature. In experiment I, conducted in the laboratory, the treatments consisted of constant temperatures of 15, 25, 30 ºC and alternating temperatures of 20-30 ºC, in the presence and absence of light. The percentage of normal seedlings, germination speed index, shoot, root and total length, total dry mass of seedlings were evaluated. The treatments were arranged in a 4 x 2 factorial design and a completely randomized design with four replications. Experiment II was carried out in the field, being sowed in tubes with two seeds each, placed in three light environments (Full sun, (0% shade), 30 and 70% shade) with four replications. The emergence percentage, emergence speed index, neck diameter, leaf number, chlorophyll SPAD index, area, root and total part length and total fresh and dry mass were evaluated. To evaluate the initial seedling growth, the seedlings were transplanted into plastic bags containing a mixture of sifted soil, sand and tanned chicken litter in a 1: 1: 0.5 ratio. The bags were placed under three light environments: full sun (0% shade) with 30 and 70% shade. Every thirty days the seedlings were evaluated for height, stem diameter, leaf number and chlorophyll index and at the end of the experiment were also evaluated, root length, internal CO2 concentration, transpiration rate, stomatal conductance, photosynthetic rate. water use efficiency, carboxylation efficiency, fresh and dry mass of leaf, stem and root. The best temperatures for P. scaberrimum Pohl seed germination were 25ºC (constant) or 20-30ºC (alternating). Shading provides increased emergence and IVE, and improves early growth of P. scaberrimum. However, seedlings in full sun and 30% shade showed better growth and quality.