Rich but not poor conditions determine sex‐specific differences in growth rate of juvenile dioecious plants

Abstract

Causes of secondary sexual dimorphism (SSD) in dioecious plants are very poorly understood, especially in woody plants. SSD is shown mainly in mature plants, but little is known about whether secondary sexual dimorphism can occur in juveniles. It is also assumed that stress conditions intensify differences between the sexes due to the uneven reproductive effort. Therefore, the following research hypotheses were tested: (1) secondary sexual dimorphism will be visible in juveniles; (2) unfavourable soil conditions are the cause of more pronounced differences between the sexes. Rooted shoots of the common yew (Taxus baccata L.) and common juniper (Juniperus communis L.), previously harvested from parental individuals of known sex were used in the study. During two growing seasons vegetation periods and four times a year, comprehensive morphological features of whole plants were measured. Some SSD traits were visible in the analysed juveniles. Contrary to expectations, differences were more pronounced in the fertilized treatment. Both species reacted to fertilization in different ways. Female yew had a clearly higher total plant mass, root mass, and mean root area when fertilized, whereas male juniper had a higher root mass when fertilized. Differences between the sexes independent of the fertilization treatment were seen, which can be interpreted as sexual adaptations to a continued reproduction. Female yews and male junipers made better use of fertile habitats. Our study showed that SSD may be innate, and sexual compensatory mechanisms could generate uneven growth and development of both sexes. Because the SSD pattern was rather different in both species, it was confirmed that SSD is connected with the specific life histories of specific species rather than a universal strategy of dioecious species.

Seed Quantity or Quality?—Reproductive Responses of Females of Two Dioecious Woody Species to Long-Term Fertilisation

“…This suggests that, although in a rich environment, female plants invest more into production of numerous flowers, while the efficiency of seed development and seed production is related to factors other than just nutritional availability and pollen availability [ 47 ]. Moreover, our earlier studies showed that fertilised female plants of both species are characterised by higher photosynthetic activity [ 38 , 48 ] and higher biomass [ 39 ] than their non-fertilised counterparts. These observations indicate that the allocation of plant resources to seed production is a reasonable/controlled investment of resource allocation; thus, in a non-fertilised environment, when the plant has already invested part of the available resource for female reproductive structure development, the necessary resources were provided by the plant (at the cost of vegetative growth or resource allocation) to ensure development of seeds [ 47 ].…”

“…T. baccata plants produce seeds within a one-year cycle with the base of the strobila developing in the autumn of the previous year, whereas in J. communis the seed-producing cycle lasts up to three years [ 35 , 37 ]. These species are characterised by gender-related ecological differences between the sexes within species [ 38 , 39 , 40 , 41 , 42 ], and population decline [ 37 , 43 , 44 ]. Thus, female plants of both species allocate resources for growth, defence, and seeds, but not pollen production, and can be great models to test the impact of long-term different nutritional availability on the female reproductive responses.…”

Covariations and trade‐offs of phosphorus (P) acquisition strategies in dioecious Populus euphratica as affected by soil water availability

“…Therefore, females were more dependent on adequate soil water for P acquisition. In humid (favourable) conditions, female individuals had higher sex‐related costs associated with greater nutrient requirements compared to males (Hultine et al, 2016; Nowak et al, 2021; Xia, He, Yu, Lv, et al, 2020). By contrast, in dry (unfavourable) conditions, males and females did not differ in leaf mineral nutrients (Dawson & Ehleringer, 1993).…”