| Effects of exogenous ABA on leaf anatomy and hormone contents of apple rootstocks |
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| DOI：10.7606/j.issn.1000-7601.2019.03.04 |
| Key Words: apple rootstocks exogenous ABA treatment leaf anatomical structure stomata traits endogenous hormone contents |
| Author Name | Affiliation | | WANG Shun-cai | College of Bioengineering and Technology, Tianshui Normal University, Tianshui, Gansu 741000, China | | LI Chao | College of Horticulture, Northwest A & F University, Yangling, Shaanxi 712100, China | | SHI Shou-guo | College of Horticulture, Northwest A & F University, Yangling, Shaanxi 712100, China | | MA Feng-wang | College of Horticulture, Northwest A & F University, Yangling, Shaanxi 712100, China |
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| Abstract: |
| The changes of leaf anatomical features and chloroplast ultrastructure of three apple grafting rootstocks, viz., Malus prunifolia, M. hupehensis and M. sieversii seedlings which were subjected to exogenous abscisic acid (ABA) for 24 h, were investigated by light microscope (LM) and transmission electron microscopy (TEM). The effects of exogenous ABA on stomatal features and endogenous hormone contents in leaves of three apple grafting rootstocks seedlings were also studied by scanning electron microscopy (SEM) and enzyme-linked immunosorbent assay (ELISA). Compared with control plants (without ABA treatment), observation of LM showed that the leaf thickness of M. prunifolia, M. hupehensis and M. sieversii decreased by 7.93%, 0.25% and 0.81%, and their palisade tissue thickness significantly decreased by 31.43%, 8.53% and 4.99% (P＜0.05), respectively. However, the sponge tissue thickness of these three apple rootstocks significantly increased by 10.34%, 6.14% and 5.63% (P＜0.05), and their scattered rate (SR) increased by 19.59%, 6.55% and 6.50%, respectively. The palisade tissue/spongy tissue (P/S) of M. prunifolia and M. hupehensis significantly decreased by 37.86% and 13.82% (P＜0.05), and their cell tightness rate (CTR) decreased by 25.46% and 8.29% under ABA treatment (P＜0.05), and then those of M. sieversii also reduced but not significantly. The upper epidermis thickness of M. prunifolia and M. hupehensis increased by 5.82% and 6.43% under ABA treatment, while that of M. sieversii significantly decreased by 26.23% (P＜0.05). The lower epidermis thickness of M. prunifolia and M. sieversii significantly increased by 12.09% and 14.21% under ABA treatment (P＜0.05), while that of M. hupehensis decreased by 12.56%. The upper and lower cuticle thickness in leaves of M. hupehensis and M. sieversii significantly increased under ABA treatment (P＜0.05), while the changes of upper and lower cuticular in leaves of M. prunifolia was not obvious. Observation by SEM indicated that the stomatal density, stomatal size, and the stomatal opening degree and rate of three apple rootstocks presented the decline of different degrees under ABA treatment. For example, those of M. prunifolia decreased by 3.62%, 7.12%×19.59%, 67.60% and 86.66%, and those of M. hupehensis decreased by 3.50%, 4.99%×20.65%, 32.42% and 58.24%, as well as those of M. sieversii decreased by 8.54%, 0.92%×12.06%, 20.37% and 16.35%, respectively. For three apple rootstocks, analysis of TEM probably indicated that chloroplast numbers in palisade tissue and spongy tissue cells reduced, thylakoid structure arranged loosely, and there was a slightly hint that starch grains in chloroplast became smaller in a shape after ABA treatment. Under ABA treatment, the contents of ABA and ZR in leaves of three apple rootstocks significantly increased (P＜0.01). Compared with the control, the contents of ABA and ZR in M. prunifolia increased by 30.83% and 13.31%, those of M. hupehensis increased by 62.40% and 45.28%, and those of M. sieversii increased by 37.07% and 17.06%, respectively. There were no obvious changes in endogenous IAA and GA levels for M. sieversii and M. prunifolia leaves between control and ABA conditions, but those of M. hupehensis significantly increased by 62.62% and 20.62% under ABA treatment (P＜0.01), respectively. Overall, the three apple rootstocks seedlings response to exogenous ABA treatment commonly have an adaptive change of xeromorphic structure between leaf anatomy and stomata traits, and the size of starch grains in chloroplast has an obvious degradation. The contents of endogenous ABA and ZR in leaves of three apple rootstocks show significant increases under ABA treatment, while the changes of endogenous IAA and GA levels are different due to their different genotypes. |
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