Effects of desiccation of seeds in nine species with morphophysiological dormancy on germination and embryo growth

Aims In species with morphophysiological seed dormancy(MPD),little is known about the effects of desiccation of imbibed seeds on embryo growth and germination.We studied seed responses to dehydration in nine species with different levels of MPD.Methods For each species,a control test was conducted by keeping seeds permanently hydrated and exposed to the optimal stratification-incubation sequenee to promote embryo growth.Simultaneously,tests were run in which seed stratification was interrupted for 1 month by desiccation at room temperature.Important Findings In Clematis vitalba and Ribes alpinum,with non deep simple MPD,desiccation affected neither embryo growth nor seed viability,but the desiccation led to a decrease of germinative ability in R.alpinum by 16%.The seeds of Narcissus pseudonarcissus subsp.munozii-garmendiae,with deep simple epicotyl MPD,tolerated desiccation in different embryo growth stages,but their germinative ability decreased slightly.The response of species with complex levels of MPD to desiccation was more variable:Delphinium fissum subsp.sordidum,with intermediate complex MPD,and Anthriscus sylvestris and Meum athamanticum,both with deep complex MPD,tolerated desiccation.In contrast,Ribes uva-crispa with nondeep complex MPD,Lonicera pyrenaica with intermediate complex MPD and Chaerophyllum aureum with deep complex MPD,had diminished germination ability by desiccation.Although seeds of the species with simple levels of MPD tolerated desiccation,those of some species with complex levels were also highly tolerant.Thus,desiccation did not induce secondary dormancy in late embryo growth stages.The desiccation tolerance of imbibed seeds of most of the nine species may show their adaptability to climate change in the Mediterranean region.

Different maternal investment strategies for male and female calves in a polygynous mammal

Mater nal effects occur whe n the phe no type of the mother in flue nces that of the young to the detriment of her survival, growth or fitn ess. The in vestment of the mother can be affected by mater nal body condition and/or experience. Trivers-Willard Hypothesis (TWH) and Local Resource Competition Hypothesis (LRCH) are the main hypotheses used to explain bias in birth sex-ratios in mammals, as well as for sex-biased maternal investment. Both hypotheses suggest that a different amount of investment must be expected according to the sex of the young. However, recent studies suggest that these differences are not in quantity but in the strategies: mechanisms and objectives may differ for each sex. We studied how maternal characteristics (age, body mass, body condition, and domi nance status) influence re leva nt aspects of the birth and early growth of the calf (birth date, birth body mass, body mass at weaning, and body condition at weaning) separately for each sex;and how that investment is mediated by milk production and composition (lactose, fat, and protein). One hundred eighty-eight newborns from 75 captive red deer hinds aged from 2 to 19 years were analyzed. The main differential investment observed was related to birth date: when producing a female, hinds give birth earlier in the season only if they have a good body condition;however, when gestating a male it is the older hinds those which deliver earlier. Subsequently, milk production and composition are correlated with birth body mass in female calves, but to weaning body mass in males. Thus, only hind body mass affects the weaning body mass of female calves, compared with age and hind body mass in males. These results suggest that while TWH fits the maternal investment strategy found for male calves, it is LRCH which correlates with the maternal investment patterns observed for females.