Photosynthetic responses to chromosome doubling in relation to leaf anatomy in Lonicera japonica subjected to water stress

Abstract

Gas exchange, chlorophyll fluorescence, and contents of some metabolites in two Japanese honeysuckle (Lonicera japonica Thunb.) cultivars, Damaohua (2n = 2x) and Jiufengyihao (2n = 4x), were compared with explore the function of chromosome doubling under water stress conditions. Water stress significantly decreased net photosynthesis rate, stomatal conductance, and transpiration rate of both cultivars. It also decreased electron transport rate, effective quantum yield of Photosystem II, photochemical quenching, and starch content, but increased non-photochemical quenching and contents of total soluble sugars, proline, and malondialdehyde. However, the tetraploid cultivar showed higher resistance to water stress than the diploid, as indicated by the fact that gas exchange, chlorophyll fluorescence, and metabolites were less affected for the tetraploid than the diploid. Moreover, the tetraploid recovered more quickly than the diploid after re-watering. Morphological and anatomical analysis further revealed that the tetraploid possessed less whole plant leaf area, higher leaf mass per unit area, thicker epidermis (both upper and lower) and palisade tissue, as well as denser pubescence. All of those specialised structures caused by chromosome doubling might lead to greater capacity in coping with drought stress. Our findings suggest that the effect of chromosome doubling on drought resistance in L. japonica could attribute to the improvement of structure and photosynthesis-related traits.

Plant responses to drought and rewatering

“…12,37 In bentgrass species, Bian and Jiang 33 reported that moderate drought and recovery only have a marginal effect on lipid peroxidation in bluegrass leaves. However, it was obviously provoked by a prolonged drought when plant leaves' RWC fell to sever dehydration level of less than 40%; 38 and as tee plants were subjected to a severe water deficit, MDA was significantly accumulated, which could be reversed drastically by rewetting, 39 indicating that whether lipid peroxidation appears or recovers strongly depends on drought intensity/duration, 33,38 and species/cultivars. 35,39 In our research, cell ion leakage, an indicator of cell integration damage, was drastically attenuated by rewatering after a relatively longterm pre-drought (30 d), albeit no reaching the normal level in well-watered plants; moreover, this occurrence was only in young leaves of Leymus chinensis, 24 implicating that the new parts of the plants might have a highly metabolically repairing capacity upon the rewatering following a pre-water-deficit stress.…”

“…Plants of Lonicera japonica Thumb. with tetraploid chromosome have a higher drought-resistance during water deficit and more rapid recovery after rewatering in terms of gas exchange and chlorophyll fluorescence compared to those with diploid chromosome, 39 showing the different responses from different genetic types. In our experiment, there was an obvious decline in F v /F m of Leymus chinensis leaves under severe soil drought, while a fully recovery appeared following refilling water.…”

Response of Organ Structure and Physiology to Autotetraploidization in Early Development of Energy Willow Salix viminalis

“…Higher ETR values were reported for the tetraploid Japanese honeysuckle (Lonicera japonica) cultivar than for the diploid one. Reduction of ETR by drought was smaller in this genotype (Li et al, 2009).…”

Tetraploid Black Locust (Robinia PseudoacaciaL.) Increased Salt Tolerance by Activation of the Antioxidant System

“…For example, li et al (24) attributed drought resistance in tetraploid L. japonica to the improvement of structure and photosynthesis-related traits. Some candidate genes in tetraploid citrus seedlings are up-regulated.…”

“…Polyploid plants are usually considered to be superior to diploid with respect to genetic adaptability and tolerance to environmental stress such as drought, heat, cold and salt (7,13,14,24,25,42,52,54). For instance, the superiority of tetraploid and hexaploid cenchru species over the diploid species is evident (9).…”