Light Affects the Chloroplast Ultrastructure and Post-Storage Photosynthetic Performance of Watermelon (Citrullus lanatus) Plug Seedlings

Abstract

Watermelon [Citrullus lanatus (Thunb.) Matsum. and Nakai] plug seedlings were stored at 15°C in the light at a photosynthetic photon flux density of 15 µmol·m−2·s−1 or in darkness for 6 days, to evaluate their chloroplast ultrastructure, and associated photosynthetic characteristics. Storage in the dark caused swelling, disordered granal arrangement, and starch grain disappearance in the chloroplasts. In contrast, the chloroplasts stored in the light were relatively normal. As a result, the light-stored seedlings had a significantly higher chlorophyll content, Fv/Fm, and Pn than did dark-stored seedlings. Regardless of whether the seedlings were stored in light or darkness, the Gs and Ls of the seedlings significantly decreased, while the Ci obviously increased when the Pn decreased after 6 days of storage. This result suggests that the decreased Pn is not solely a stomatal effect, as the effects on the chloroplasts contributed to this photosynthetic inhibition. Six days after transplanting, seedlings that were stored in the light or darkness for 2 or 4 days showed complete recovery of chloroplast ultrastructure, chlorophyll content, Fv/Fm, Gs and Pn. When the storage period increased to 6 days, the dark-stored seedlings had a significantly lower Fv/Fm and Pn than the light-stored and control seedlings 6 days after transplanting, which was mainly ascribed to incomplete recovery of chloroplast ultrastructure. Furthermore, the light-stored seedlings exhibited a significantly higher shoot dry weight during storage and a higher percentage dry weight increase after transplanting than the dark-stored seedlings. These effects were enhanced by prolonged storage (4 to 6 days). This study demonstrated that dim light during storage is beneficial for maintaining chloroplast ultrastructure as well as photosynthetic efficiency in watermelon seedlings, thus contributing to the rapid recovery of post-storage photosynthetic performance, which ensures the transplant quality of the seedlings after removal from storage.

Effect of light on ultrastructure of chloroplasts and post-storage performance of Hydrangea macrophylla (Hydrangeaceae)

“…Grana were stacked in parallel with the prevailing plane of thylakoid lamellae. On the contrary, we highlighted that dark storage significantly modified both the Chl content and the chloroplast ultrastructure of the leaves, confirming that chloroplast development depends on light, and light affects chloroplast structure and photosynthetic changes in plants (Duan et al 2014, Mathur et al 2018. Indeed, leaves of Hydrangea macrophylla stored for a long time (12 or 15 d) in dark conditions showed drastic modifications of the chloroplasts, which were smaller in size and present in smaller numbers (Fig.…”

“…Indeed, photosynthesis is among the plant cell functions that are highly sensitive to any type of changes, such as water deficit (Pinheiro and Chaves 2011), high temperature (Song et al 2014), UV radiation (Fonini et al 2017), and mainly the low light intensity (Darko et al 2014, Ruban 2015, Wang et al 2015, Mathur et al 2018. The quantity and quality of light affects the photosynthetic apparatus of plants during storage and during the subsequent recovery period (Duan et al 2014). Chloroplasts are main organelles of photosynthesis and their morphology is closely linked to photosynthesis.…”

“…Few studies have been carried out on the effects of storage and the subsequent recovery period on photosynthetic apparatus of ornamental plants and on anatomical and morphological ultrastructure modification (Duan et al 2014). The present knowledge on the effects of irradiance on chloroplast structure and associated photosynthetic capacity of Hydrangea is still insufficient.…”

“…Contradictory data on the recovery of the chloroplast ultrastructure after light or dark storage can be found in the literature. Seedlings of watermelon, Citrullus lanatus, which were stored in the dark for 6 d, did not recover their thylakoid structure 6 d after transplantation (Duan et al 2014). On the contrary, leaves of Cucurbita pepo stored in the dark for 5 d showed normal chloroplasts 5 d after transplanting into light conditions (Ananieva et al 2004).…”

Reducing the Excessive Evaporative Demand Improved the Water-use Efficiency of Greenhouse Cucumber by Regulating the Trade-off between Irrigation Demand and Plant Productivity

“…Two photosynthesis systems were used to enable simultaneous gas exchange measurements. Stomatal limitation (Ls) was estimated according to Ls =1 -C i /C a , where C i is the intercellular carbon dioxide (CO 2 ) concentration and C a is the ambient CO 2 concentration (Duan et al, 2014). Instantaneous WUE (InstWUE) at the leaf scale was calculated as the amount of carbon gain in photosynthesis rate (P n ) per unit of water transpired (T r ): InstWUE = P n /T r (Xu and Zhou, 2008).…”