Variation of mean indicators that characterize stomata and the density of stomata location on leaf surface.
Vegetation growth peculiarities and morphological and physical-biochemical features of Prunus domestica L. Utro and Yaichnaya Sinyaya varieties leaves grafted on different growing strength rootstocks were studied. Low-growing clonal rootstocks 140–1 and Novinka decreased the trees growing strength on 15–20% in comparison with strong-growing stocks; medium-growing rootstocks OPA-15-2 and OP-23-23 reduced it on 10%. The longest growing activity and the largest sprouts length was stated on these rootstocks as well, i.e. 1.3–1.4 times more than on other ones. Stable sprouts average length decrease was registered on grafted stocks 140–1 and Novinka. Leaf surface index value on the trees grafted on clonal rootstocks OPA-15-2 and OP-23-23 was on 40% higher than on control, i.e. 4.3 leaves m2/crown projection area m2. Optimal values of total increment, sprouts average length, leaves area and the largest part of physiological-biochemical parameters were stated at medium-growing clonal rootstocks OPA-15-2 and OP-23-23 use. Plum leaves blades were hypostomatic; numerous stomata were located on the abaxial (bottom) side of leaves. Stomata were located in interveinal space irregularly. Stomata length size varied from 14.6 μm (Utro/seedlings) to 22.1 μm (Yaichnaya Sinyaya/OP-23-23). The rootstock has influence on the process of photosynthesis, antioxidant activity, accumulation of minerals and metabolic answerin the leaves.
- Prunus domestica L.
- scion-stock combinations
- growth and development
- scanning electronic microscopy
- physiological parameters
The popularity of domestic plum (
Many questions devoted to plum varieties propagation and scion-stock combination selection are successfully solved in the world; at the same time, the life length of grafted plants and the harvest quality depending on a variety and a rootstock are not studied enough. The major part of the researches in this branch of study were held by [6, 7, 8], who found out that photosynthesis intensity varies depending on a variety and scion-stock combination. The influence of rootstock on the quality of plum fruits is shown in the works [9, 10].
This present study was planned to analyze the least studied morphological and biochemical characteristics, i.e. – growing activity and the sprouts length, lea fsurface index on the trees, Stock influence on leaf morphological features and parameters, on photosynthetic pigments synthesis, on antioxidant activity and phenol compounds sum accumulation in plum leaves, on ash composition and on
2. Studies results
2.1 Studies place, objects and methods
The field researches were held in 2018–2020 on the experimental
The leaves of
The biochemical researches were held in the Laboratory of Biochemistry and Physiology of FHR CBAN.
The understudied parameters included field registration (the trees growth, the crown volume, the total sprouts increment, leaf surface area) and the leaves laboratory studies (comparative micromorphology of the leaf adaxial and abaxial sides, stomata number and size, photosynthetic pigments content, antioxidant activity, phenolic compounds sum, ash composition and quality content of the leaves main metabolites). The leaves microsculpture and ash composition were determined on analytical REM JEOL JSM – 6010 LA (JEOL Ltd., Japan). Photosynthetic pigments Chl a and b and total carotenoids (Car) were studied on spectrophotometer Helios Υ UV–vis (USA) in accordance with the method , total phenolic amount was determined with Folin–Ciocalteu reagent in accordance with the method  and total antioxidant capacity the scavenging activity for the 2,2-dipheny l-1-picrylhydrazyl (DPPH) radical was determined in accordance with the method .
Metabolites quality composition, contained in plum leaf extracts was analyzed on JEOL JMS-Q1050GC (JEOL Ltd., Japan) via the method of gas chromate-mass-spectrometry in accordance with the method .
2.2 Stock influence on growth parameters
Stock influence on trees growth parameters were studied using tree height, crown volume, one-year-old sprout length, leaf surface area. Utro variety 8-year-old tree height was within the range of 2.8 m (140–1) – 3.2 m (seedlings). Yaichnaya Sinyaya variety height differences determined by stock were 0.6 m, and height varied from 3.1.m (140–01) to 3.7 m (seedlings). In comparison with strong-growing seedlings low-growing rootstocks 140–1 and Novinka reduced tree growing strength on 15–20%, medium-growing stocks OPA-15-2 and OP-23-23 – on 10%.
Depending on a rootstock, plum trees crown volume was within the range of 11.5 m3 (Yaichnaya Sinyaya/140–1) – 14 m3 (Yaichnaya Sinyaya/OP-23-23). Utro variety crown volume varies insignificantly on different rootstocks (12–13 m3).
Plum trees growing process intensity are characterized by active sprout growth duration and total one-year-old sprouts length. Domesticated plum active growth duration was from 32 days (Utro variety) to 40 days (Yaichnaya Sinyaya variety), and depending on a rootstock the fluctuations were 8–11 days. The longest active growth duration was registered on 140–1 and OP-23-23 rootstocks.
Average sprouts length that characterizes tree general state was within wide ranges, i.e. from 9.0 cm (Utro/Novinka) to 22.8 cm (Yaichnay Sinyaya/OP-23-23) and was 25.0 cm at average. At Yaichnaya Sinyaya variety this parameter was stable depending on a rootstock (18–22 cm) and 1.5 times higher than at Utro variety (Figure 2).
Stable reduction of average sprouts length was stated on grafted 140–1 and Novinka rootstocks. On OPA-15-2 and OP-23-23 rootstocks this parameter was 1.3–1.4 times higher (Figure 3).
The main indicator of growing processes activity is total sprouts length. This parameter was significantly less at the trees grafted on clonal rootstocks, i.e. 140–1 (110 m) and Novinka (120 m). On medium-growing OPA-15-2 and OP-23-23 sprouts buildup was 170–180 m and 1.2 times bigger than on seedlings.
The main indicator that characterizes plum tree crown leaf coverage level is leaf surface area. The size of the leaves varied significantly depending on the scion-rootstock combination (Figure 3).
Leaves area was within the range of 21.4 m2/tr. (Yaichnaya Sinyaya/seedlings) – 36.2 m2/tr. (Utro/OPA-15-2). At Utro variety the differences between low and strong-growing rootstocks were 9–11 m2/tr., and at Yaichnaya Sinyaya variety – 6-8 m2/tr. More higher values at that were closer to physiological optimum. i.e. more than 30 m2/tr., were registered on grafted OPA-15-2 and OP-23-23 rootstocks. Less assimilation apparatus was formed on low-growing 140–1 rootstock than on control.
Plum trees leaf surface index depending on a combination was within the range of 4.3–7.2 leaves m2/crown projection area m2. Leaf surface index maximum values, i.e. 7.2 leaves m2/crown projection area m2, were registered at scion-stock combinations Utro/OPA-15-2 and Yauchnaya Sinyaya/OP-23-23. Leaf surface index value was on 40% at the trees grafted on OPA-15-2 and OP-23-23 rootstocks than on control, i.e. 4.3 leaves m2/crown projection area m2.
The main indicators of domesticated plum trees vegetative productivity, i.e. crown volume, total sprouts buildup, leaf surface area, depended not only on a variety, but also on a rootstock. Optimal values of total buildup, average sprouts length, leaves area were registered on medium-growing clonal OPA-15-2 and OP–23–23 rootstocks.
2.3 Stock influence on leaf morphological features and parameters
Morphological differences of various varieties leaves were studied using scanning electron microscopy (SEM). Adaxial epidermis consists of thick cells layer. Their surface is covered with firm cuticle with numerous folds or in the form of long stripes and colpi, microsculptural differences are presented in Figure 4. Plum leaves blades were hypostomatic; numerous stomata were located on the abaxial (bottom) side of leaves (Figure 5). Grafted plants leaves, as a rule, had well-developed rollers around stomata. Stomata were located in interveinal space irregularly. Stomata length size varied from 16.42 μm (Utro/seedlings) to 22.11 μm (Yaichnaya Sinyaya/OP-23-23). It is typical that the ratio of stomata length to their width, at variety-stock combinations was larger than at a rootstock. Such regularity was stated for all variety-stock combinations. Stomata density varied significantly from 436 ± 9 (Yaichnaya Sinyaya/OP-23-23) to 1000 ± 17 (Utro/seedlings) stomata on mm2 at. Variation of mean indicators that characterize stomata and the density of stomata location on leaf surface are shown in Table 1 using the example of the Utro variety.
|Stick-stok kombination||Number of stomata/mm2||Stomata length||Stomata width||Stomatal index|
|Utro/seedlings||1000 ± 17||17.59 ± 0.14||9.57 ± 1.11||1.8|
|Utro/Novinka||800 ± 13||19.22 ± 1.24||11.23 ± 1.11||1.7|
|Utro/140–1||689 ± 21||16.42 ± 2.11||8.32 ± 1.14||1.9|
|Utro/OP–23–23||556 ± 22||18.26 ± 2.11||8.94 ± 0.85||2.0|
2.4 Stock influence on photosynthetic pigments synthesis
Chlorophylls Chl a and Chl b content is one of the main indicators of domesticated plum trees vegetative productivity. Chl a content is 3–4 times higher than Chl b one at average and varies from 4.12 mg/ml (seedlings) to 13.71 mg/ml (OP-23-23). Chl a + Chl b sum content increase and the highest ratio Chl a/b were registered in Yaichnaya Sinyaya and Utro leaves on OPA-15-2 rootstocks and OP-23-23, that lead to higher intensity of photosynthesis process (Figure 6). The highest carotenoids content was registered in OP-23-23 rootstock leaf extracts (1.26 mg/ml), Utro/Novinka (0.9 mg/ml), Utro/OP-23-23 (0.79 mg/ml) and Yaichnaya Sinyaya (0.75 mg/ml) combinations (Figure 7). Consequently, photosynthetic pigments synthesis depended not only on a genotype, but also on a used rootstock.
2.5 Stock influence on antioxidant activity and phenol compounds sum accumulation in plum leaves
The capacity of plum leaf extracts to scavenge DPPH+ free radicals, which has been used as a measure of total antioxidant capacity (AA), and total phenolic content (TPC) are shown in Table 2. AA speaks about the presence of biologically active substances-antioxidants that are synthesized in plum leaves. Average AAA and AAM of ethanol extracts was 88.7%; average AA of water extracts was 73.8%. The maximum AAA (90.72%) and AAM (92.12%)values were registered in the leaves of Yaichnaya Sinyaya/Novinka combination; the minimal values were stated in the leaves of strong-growing
|Strong-growing ||88.14 ± 1.14||57.08 ± 1.11||13.68 ± 0.24|
|Yaichnaya Sinyaya/strong-growing ||89.76 ± 2.01||68.11 ± 1.21||16.48 ± 0.31|
|OPA–15–2||89.71 ± 1.14||79.15 ± 1.08||6.23 ± 0.21|
|Yaichnaya Sinyaya/OPA–15–2||88.55 ± 2.11||47.61 ± 0.89||11.42 ± 0.22|
|Novinka||90.72 ± 1.46||82.38 ± 1.24||9.83 ± 0.11|
|Yaichnaya Sinyaya/Novinka||88.51 ± 1.34||79.19 ± 2.01||14.63 ± 0.21|
|OP–23–23||90.55 ± 1.51||75.77 ± 2.12||9.19 ± 0.31|
|Yaichnaya Sinyaya/OP–23–23||90.72 ± 1.34||92.12 ± 2.13||14.51 ± 0.42|
|140–1||89.71 ± 1.24||79.31 ± 1.06||14.93 ± 0.61|
|Yaichnaya Sinyaya/140–1||89.36 ± 1.40||77.35 ± 1.42||23.48 ± 0.42|
2.6 Stock influence on plum leaves ash composition
12 ash elements, i.e. P, S, K, Ca, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, were studied. The decreasing row of the elements content in the plum leaves ash is the following: K > Ca > Co > Mg > P ≈ S > Cu ≈ Zn > Fe > Mo > Cr ≈ Ni.
The principal proportion of the leaves ash composition was K, which was accumulated up to 25 mass % and Ca up to 10 mass % in ash (Figure 9). The maximum content of K is noted in the leaves of Yaichnaya Sinyaya and Novinka on OP-23-23 combination; the minimal values were stated in the leaves of strong-growing
The certain oligo-elements Mo and Ni weare contained with in the range of from 1.2 (140–1) to 3.2 (Utro/OP–23–23) mass % – Cu and Ni from 2.1 (Yaichnaya Sinyaya/140–1) to 5.6 (Utro/140–1) mass % (Figure 12).
2.7 Stock influence on plum leaves metabolic answer
Metabolites component composition of rootstocks and scion-stock combinations leaves was fulfilled using the method of gas chromate-mass-spectrometry. Comparative chromatogram of Yaichnaya Sinyaya/seedlings combination with other combinations are given in Figure 13. In the whole, chromatographic profiles are alike and are characteristic for
Such information is useful for the grafted plants physiology evaluation and scion-stock combination choice.
We would like to thank Mariya Mertvishcheva and Darya Panishcheva for assistance in determining photosynthetic pigments, antioxidant activity and phenolic compounds sum and for metabolites analysis probes preparation.
Conflict of interest
The authors declare no conflict of interest.