Physiological Adaptive Strategies of Oil Seed Crop Ricinus communis Early Seedlings (Cotyledon vs. True Leaf) Under Salt and Alkali Stresses: From the Growth, Photosynthesis and Chlorophyll Fluorescence

Abstract

Ricinus communis is an important energy crop and is considered as one of the most potential plants for salt-alkali soil improvement in Northeast China. Early seedling stage (such as the cotyledon expansion stage) is always a vulnerable stage but plays a vital role in plant establishment, especially under stress conditions. However, little information exists concerning the function of cotyledon and the relationship between cotyledon and true leaf in the adaptation to salt stress and alkali stress of this species. Here, Ricinus communis seedlings were treated with varying (40, 80 and 120 mM) salinity (NaCl) and alkalinity (NaHCO3), growth, photosynthesis, and chlorophyll fluorescence of cotyledons and true leaves were measured. The results showed that the biomass, photosynthetic parameters, and the qp value of both cotyledons and true leaves decreased with increasing salt-alkali stress, and the decrease in biomass, gs and Tr, of true leaves were much greater than that of cotyledons. Salt-alkali stress only reduced photosynthetic pigments and ΦPSII in cotyledons, but did not affect those in true leaves. Additionally, the Fv/Fm and NPQ between cotyledons and true leaves showed different trends in salinity and alkalinity. The results suggested that alkali stress could cause much more damage to the castor bean seedlings, and different physiological responses and adaptive strategies are found in cotyledons and true leaves under salt-alkali stress. This study will help us develop a better understanding of the adaptation mechanisms of cotyledon and true leaf during early seedling stage of castor bean plant, and also provide new insights into the function of cotyledon in Ricinus communis under salt-alkali stress conditions.

Metabolomics Analysis Reveals the Alkali Tolerance Mechanism in Puccinellia tenuiflora Plants Inoculated with Arbuscular Mycorrhizal Fungi

“…Seedling establishment is one of the most sensitive and important stages of plant development in alkali-degraded soil [40]. In the present study, the dry weight of P. tenuiflora seedlings with or without AM decreased.…”

The Effect of Arbuscular Mycorrhizal Fungi on Photosystem II of the Host Plant Under Salt Stress: A Meta-Analysis

“…A previous study reported that an increase in NPQ is thought to be an energy dissipation mechanism that protects the photosynthetic apparatus against excess light under salt stress [31]. Many studies reported an observed increase in NPQ in AMF-inoculated plants under salt stress [12,14]. These results indicate that AMF inoculation could improve the energy dissipation ability of a plant, which protects the photosynthetic apparatus against excess light under salt stress [15,32].…”

“…Chlorophyll fluorescence is a rapid, non-destructive method to determine changes in photosystem II and is used in many fields [29]. The Fv/Fm value can reflect the photo-inhibition level of PS II by estimating the maximum quantum yield of primary acceptor (QA) reduction [12]. A positive total impact on the Fv/Fm values of host plants under salt stress was confirmed in the present study, showing that AMF inoculation could alleviate photo-damage to PS II caused by stress [13].…”

“…Many studies have also used chlorophyll fluorescence analysis to evaluate the positive effect of AMF on the photosynthetic capacity of the host plant under salinity stress, including Oryza sativa [7], Jatropha curcas [11], and Zea mays [8]. Chlorophyll fluorescence is a rapid, non-destructive method to examine the stress features and photosynthetic performance of a plant [12]. These parameters can clearly reflect several aspects of photosynthesis, such as energy-utilizing strategies, the conditions in the PS II reaction center, photosynthetic electron transport, and photophosphorylation [13].…”

Influence of Cathodic Water Invigoration on the Emergence and Subsequent Growth of Controlled Deteriorated Pea and Pumpkin Seeds

“…Furthermore, "hangover effects" of deterioration may be carried through to later growth stages of the plant. Seedlings of deteriorated seeds may display reduced photosynthesis and transpiration [10,11], slower growth and ultimately lower yields [12]. Thus, even if poor quality seeds germinate or emerge, the quality of plants generated from such seed is not guaranteed [7,10,11].…”