Institute for Horticultural Production Systems, Leibniz-University Hannover, Hannover, Germany.
PLoS One. 2021 Oct 13;16(10):e0258521. doi: 10.1371/journal.pone.0258521. eCollection 2021.
Russeting compromises appearance and downgrades the market value of many fruitcrops, including of the mango cv. 'Apple'. The objective was to identify the mechanistic basis of 'Apple' mango's high susceptibility to russeting. We focused on fruit growth, cuticle deposition, stress/strain relaxation analysis and the mechanical properties of the cuticle. The non-susceptible mango cv. 'Tommy Atkins' served for comparison. Compared with 'Tommy Atkins', fruit of 'Apple' had a lower mass, a smaller surface area and a lower growth rate. There were little differences between the epidermal and hypodermal cells of 'Apple' and 'Tommy Atkins' including cell size, cell orientation and cell number. Lenticel density decreased during development, being lower in 'Apple' than in 'Tommy Atkins'. The mean lenticel area increased during development but was consistently greater in 'Apple' than in 'Tommy Atkins'. The deposition rate of the cuticular membrane was initially rapid but later slowed till it matched the area expansion rate, thereafter mass per unit area was effectively constant. The cuticle of 'Apple' is thinner than that of 'Tommy Atkins'. Cumulative strain increased sigmoidally with fruit growth. Strains released stepwise on excision and isolation (εexc+iso), and on wax extraction (εextr) were higher in 'Apple' than in 'Tommy Atkins'. Membrane stiffness increased during development being consistently lower in 'Apple' than in 'Tommy Atkins'. Membrane fracture force (Fmax) was low and constant in developing 'Apple' but increased in 'Tommy Atkin'. Membrane strain at fracture (εmax) decreased linearly during development but was lower in 'Apple' than in 'Tommy Atkins'. Frequency of membrane failure associated with lenticels increased during development and was consistently higher in 'Apple' than in 'Tommy Atkins'. The lower rate of cuticular deposition, the higher strain releases on excision, isolation and wax extraction and the weaker cuticle account for the high russet susceptibility of 'Apple' mango.
皱皮降低了许多水果作物的外观和市场价值，包括芒果 cv. 'Apple'。本研究旨在确定 'Apple'芒果高度易皱皮的机制基础。我们专注于果实生长、角质层沉积、应力/应变松弛分析和角质层的机械性能。非易感芒果 cv. 'Tommy Atkins' 作为对照。与 'Tommy Atkins' 相比，'Apple' 果实的质量较低，表面积较小，生长速度较慢。'Apple'和 'Tommy Atkins' 的表皮和下皮细胞几乎没有差异，包括细胞大小、细胞方向和细胞数量。气腔密度在发育过程中下降，'Apple'中的气腔密度低于 'Tommy Atkins'。平均气腔面积在发育过程中增加，但 'Apple'中的面积始终大于 'Tommy Atkins'。角质层膜的沉积速率最初很快，但后来减慢，直到与面积扩张速率相匹配，此后单位面积的质量基本保持不变。'Apple'的角质层比 'Tommy Atkins'薄。随着果实生长，累积应变呈 S 形增加。在切除和隔离（ε exc+iso）以及蜡提取（ε extr）时释放的应变（ε exc+iso）在 'Apple'中高于 'Tommy Atkins'。在发育过程中，膜硬度增加，'Apple'中的膜硬度始终低于 'Tommy Atkins'。膜断裂力（Fmax）在发育中的 'Apple'中较低且恒定，但在 'Tommy Atkin'中增加。膜断裂时的应变（ε max）在发育过程中呈线性下降，但 'Apple'中的应变低于 'Tommy Atkins'。与气腔相关的膜失效频率在发育过程中增加，且在 'Apple'中始终高于 'Tommy Atkins'。角质层沉积率较低、切除、隔离和蜡提取时释放的应变较高以及角质层较弱是 'Apple'芒果高度易皱皮的原因。
