Dormancy Release and Seed Germination in Tulipa saxatilis (Liliaceae) Coupled with Effects of Fertilization Schemes for Bulblet Development from Seedlings

Abstract

Tulips are among the most famous plants that are used mainly as ornamental cut flowers. Although widely cultivated, they are mainly reproduced asexually, and knowledge of their sexual reproduction is imperfect, especially in regard to botanical tulips. The aim of the present study was to investigate the temperature effect on seed germination of the Near Threatened wild-growing Greek subendemic plant Tulipa saxatilis (Liliaceae) and to define its seed dormancy type. Seed germination was facilitated by bioclimatic profiling generated with R software (version 4.3.3) connecting its natural distribution points with open access precipitation and temperature data, and it was assessed upon incubation in controlled growth chambers at five constant temperatures (5, 10, 15, 20 and 25 °C) under a 12:12 light–dark photoperiod. The seeds were dependent on temperature for germination and germinated only within a very narrow range of relatively low temperatures (5–15 °C) and optimally at 10 °C (93%), corresponding to natural winter temperatures and precipitation profiles. Increase in the incubation temperature at 20 and 25 °C resulted in no germination. The treatment of seeds with gibberellic acid (GA3) at two different concentrations (500, 1000 mg·L−1) did not widen the temperature range for seed germination. The seeds of T. saxatilis initially presented an underdeveloped embryo, and significant embryo development was detected only at low temperatures (10 and 15 °C) with almost triple embryo length after one month, thus confirming the existence of complex morphophysiological seed dormancy. Moreover, germinated seeds (with and without GA3) were planted in small-sized pots under greenhouse conditions, and the growth of bulblets was investigated in response to the application of commercially available chemical fertilizers, an integrated nutrient management scheme, and a biostimulant. The fertilization schemes affected the weight and length of the produced bulblets, whereas initial seed treatment with GA3 negatively affected the growth (weight, length, and width) of the produced bulblets.