Reproduction studies, particularly embryology, represent basic information of any plant. However, the current embryological information is fragmentary for Kentucky bluegrass (Poa pratensis L.). Here, paraffin sections were used to examine the cyto-embryological characteristics, including microsporogenesis, microgametogenesis, megasporogenesis, megagametogenesis, and apomixis, of wild Kentucky bluegrass germplasm from Gannan (GN) and Longnan (LN) in Gansu Province. The study found no significant differences in pollen diameter, characteristics, viability, and stigma receptivity between the two germplasm materials. The Kentucky bluegrass consisted of three anthers, and each contained four pollen sacs that were divided into left and right halves. After meiosis, the microspore mother cells formed dyads and tetrads, which were primarily symmetrical and underwent mitosis to form three-celled pollen. Kentucky bluegrass has a one-locular ovary, two-feathery stigmas, thick nucleolar and anatropous ovules, and a typical polygonum embryo sac as its reproductive organs. The main type of apomixis observed was apospory, resulting in the coexistence of multiple embryo sacs. Polyembryonic seeds were frequently observed in Kentucky bluegrass due to apospory. Most importantly, our research found that apospory caused early embryogenesis during fertilization, which is a vital embryological feature for identifying sexual reproduction and apomixis in Kentucky bluegrass. Sexual reproduction followed strict double fertilization, while in apomixis a complete seed was only formed through pseudogamy. These embryological characteristics are documented here, and their study can aid in understanding the evolution of Kentucky bluegrass.

Rhizome-rooted alfalfa (Medicago sativa L.) is an excellent forage for establishing grazing and ecological grasslands, requiring a high and stable yield. Studying the genetic and physiological basis of stable expression of biomass traits is essential for improving production performance in rhizome-rooted alfalfa. We analyzed forage mass and photosynthetic physiological indices of the improved progenies (RSA−01, RSA−02, and RSA−03), parental “Qingshui” (CK₁), and “WL168” (CK₂) at ages one and five years and their relationships, then revealed heterotic stability. Moreover, we explored the effects of interannual dynamics and genetic differences on tested indices. The results revealed compared with the forage mass of CK₁, RSA−03 at ages one and five years increased by 22.17% and 19.72%, respectively, while RSA−01 and RSA−02 varied from 1.40% to 8.65%, indicating obvious heterosis in forage mass of RSA−03. At one year of age, G_s value, Car content and SS content of RSA−03 were higher than those of CK₁; SS content of RSA−03 were higher than those of CK₂ and RSA−02; C_i, G_s and T_r values of RSA−03 were higher than those of RSA−01. At five years of age, P_n, G_s, and WUE values, and Sta content of RSA−03 were higher than those of CK₁; C_i value and Suc content of RSA−03 were higher than those of CK₂; Car content and G_s value of RSA−03 were higher than those of other progenies. The forage mass; Chl(a/b) ratio; P_n, G_s, and WUE values; Suc content of RSA−03 at age five years were higher than those at age one year by 9.99%–44.24%. Through path analysis, G_s and NSC were direct factors affecting forage mass at age one year, and both P_n and SP affected forage mass indirectly through G_s; G_s and Chl(a+b) were direct factors affecting forage mass at age five years, and SS affected forage mass indirectly through G_s. Interestingly, Chlb, Chl(a/b), P_n, T_r, G_s, C_i, Suc, SP, and SS were more influenced by age than genetics, while the opposite was true for Car and Sta. Accordingly, RSA−03 showed obvious and stable heterosis in forage mass and photosynthetic physiology, recommending the establishment of grazing pastures and ecological vegetation.