Thermal and hydrotime requirements for seed germination can vary with the species, environment in which the seeds developed and/or seed mass. We investigated seed germination responses to temperature and water potential of Aspidosperma quebracho-blanco, Bulnesia retama, Parasenegalia visco, Parkinsonia praecox and Tecoma stans, all of which are native tree species of Chaco seasonally dry forests in northwest Argentina. We determined inter-and intraspecific variability in seed germination through thermal and hydrotime models and correlated model parameters with environmental variables of seed provenance and seed mass. Seeds of all species germinated to high percentage over a range of temperatures. Seeds of A. quebracho-blanco, P. praecox and T. stans were more tolerant to water stress than those of B. retama and P. visco. Thermal and hydrotime parameters for germination varied amongst species and populations. There was a negative correlation between thermal (θ_T(50)) and hydrotime (θ_H) constants and base temperature (T_b) and water potential (Ψ_b(50)). Seed mass correlated negatively with T_b and positively with θ_T(50). Species and populations were grouped according to thermal and hydrotime parameters and seed mass but not according to seed provenance. These results suggest that seed germination traits related to temperature, water potential and seed mass are species specific, and the variations within a species are probably due to a high phenotypic plasticity. These species showed a complex set of germination strategies that give them a competitive advantage in different environments, depending on dispersal time, seed mass and local environmental conditions during the germination period.

中文翻译：

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与种群环境条件和种子质量相关的查科季节性干旱森林物种种子萌发的热量和水时间要求的变化

种子萌发所需的热量和水力时间会随着种子发育的物种、环境和/或种子质量的不同而不同。我们调查了Aspidosperma quebracho-blanco、Bulnesia retama、Parasenegalia visco、Parkinsonia praecox和Tecoma stans的种子萌发对温度和水势的反应，这些植物都是阿根廷西北部查科季节性干旱森林的原生树种。我们通过热和水时模型确定种子萌发的种间和种内变异性，并将模型参数与种子来源和种子质量的环境变量相关联。所有物种的种子在一定温度范围内发芽的比例都很高。种子A. quebracho-blanco、P. praecox和T. stans比B. retama和P. visco更能耐受水分胁迫。发芽的热力和水力时间参数因物种和种群而异。热常数 ( θ _T(50) ) 和水力时间 ( θ _H ) 常数与基础温度 ( T _b ) 和水势 ( Ψ _{b( 50 )} )之间存在负相关。种子质量与T _b负相关，与θ _{T正相关(50)}. 物种和种群是根据热和水时参数以及种子质量而不是根据种子来源进行分组的。这些结果表明，与温度、水势和种子质量相关的种子萌发性状是物种特异性的，物种内的变异可能是由于表型可塑性高。这些物种表现出一套复杂的发芽策略，使它们在不同环境中具有竞争优势，具体取决于发芽期间的传播时间、种子质量和当地环境条件。