Soil water deficit impacts cold acclimation and freezing tolerance in creeping bentgrass (Agrostis stolonifera L.), but the mechanisms underlying have not been well understood. The objectives of this study were to investigate the effects of deficit irrigation before and during cold acclimation on osmoprotectants, antioxidant metabolism, and freezing tolerance in creeping bentgrass. The grass was subjected to three-soil moisture levels: well-watered [100% container capacity (CC)], deficit irrigation induced-mild drought stress (60% CC), and severe drought stress (30% CC) for 35 days including 14 days at 24/20 °C (day/night) and then 21 days under cold acclimation treatment (2 °C) in growth chambers. Leaf proline and total soluble sugar (TSS) levels were higher in the grass under mild drought stress relative to that under severe drought stress. Superoxide (O2−·), hydrogen peroxide (H2O2), and malondialdehyde (MDA) content were higher in the grass under severe drought relative to that under well-watered and mild drought stress at day 35. Mild drought stress increased catalase (CAT) and guaiacol peroxidase (POD) activity, induced new isoforms and increased band intensities of superoxide dismutase (SOD), CAT, and POD during cold acclimation (days 14 to 35). No differences in osmoprotectants, antioxidant metabolism, and freezing tolerance were found between mild drought and well-watered treatments. The results of this study suggest deficit irrigation-induced mild drought stress in late fall and winter could induce accumulation of osmoprotectants and improve antioxidant metabolism, and freezing tolerance, but severe drought stress could reduce freezing tolerance of creeping bentgrass in the region with limited precipitation.
Improving the poor resistance to environmental stress and the weak development of roots system in the cherry (Prunus) rootstock ‘Gisela 6’ (Prunus cerasus × Prunus canescens) is of great importance for sustainable sweet cherry (Prunus avium) production. Although a stable genetic transformation system has been developed for ‘Gisela 6’ rootstock, there is little information on the identification of genes involved in stress resistance. Using the cherry rootstock cultivar Gisela 6, we identified a total of 12 novel mitogen-activated protein kinase (MAPK) genes, designated PcMPKs. Phylogenetic analysis revealed that the PcMPKs could be divided into four groups, designated A, B, C, and D. In addition, an intron–exon structure analysis for the PcMPKs was conducted to help further understand the structure–function relationships within the cherry family. The expression profiles of PcMPKs in response to abiotic and biotic stresses were characterized using quantitative reverse transcription-polymerase chain reaction (qRT-PCR). Five PcMPKs (i.e., PcMPK4-1, PcMPK4-2, PcMPK3, PcMPK6, and PcMPK18) exhibited differential expression, and suggested their potential roles in plant responding to various stresses. This study provides the basis for further analysis on the physiological functions of PcMPKs in environmental tolerance in cherry rootstocks.
Albino tea plants are mutants that grow albino young leaves owing to lack of chlorophylls under certain environmental conditions. There are two types of albino tea plants grown in production, i.e., light- and temperature-sensitive albino tea cultivars. The former grows albino leaves in yellow color under intensive sunlight conditions and the later grows albino leaves with white mesophyll and greenish vein as the environmental temperature is below 20 °C. Both albino teas attract great attention because of their high levels of amino acids and the “umami” taste. There have been many studies focusing on the temperature-sensitive albino tea plants, whereas little attention has been given to the light-sensitive albino tea cultivars. The characteristics of the albino tea cultivars and the mechanism underlying them were reviewed in the present article based on the published literatures, including chemical compositions, morphological characteristics, and molecular genetic mechanism.