ЭКСПЕРИМЕНТАЛЬНЫЕ СТАТЬИ
УДК 581.1
DEVELOPMENT OF TYLOSES IN THE XYLEM VESSELS OF MEILI GRAPEVINE AND THEIR EFFECT ON WATER TRANSPORTATION1 © 2014 X. H. Zhao***, L. Y. Liu***, L. J. Nan***, H. Wang***, H. Li***
* College of Enology, Northwest A&F University, Yangling, Shaanxi, China ** Shaanxi Engineering Research Center for Viti-Viniculture, Yangling, Shaanxi, China
Received October 30, 2012
Shoot pruning could cause short-term damages to vines. In response to damage, tyloses develop in shoot xy-lem vessels interfering free water and mineral transportation. In this study, the tylosis development at different nodes of the current-year and perennial shoots of sixty three-year-old grapevines (Vitis vinifera L.) after pruning was investigated. The results showed that tyloses at the nodes closest to the trunk developed rapidly; and tylosis development initiated at the time when the size of vessel-ray pit was greater than that of parenchyma cell-parenchyma cell pit. In current-year shoots, tyloses were formed in up to 87% of the vessels, and 40% of the vessels were completely blocked by tyloses. In wound-induced perennial shoots, 30% of the vessels were completely blocked by tyloses. When few vessels were blocked by tyloses, new vessels could differentiate, and water transportation system may be restored. However, when tyloses developed in a large number of vessels and the large number of the vessels were blocked, the original capability of water transport was decreased (the largest decrease was 21.1% in this study), resulting in dehiscence or shrinkage cracking in this area. The study proved that the tylosis formation in functional vessels limited the water transport efficiency.
Keywords: Vitis vinifera - pruning - tyloses - xylem vessels - water transportation
DOI: 10.7868/S0015330314020201
INTRODUCTION
Vessel is constructed of highly specialized cells, the vessel elements, and perforation plates formed onto its end wall with secondary thickening of the side wall. During the evolution of land plants, these vessel elements developed their features to transport water and minerals efficiently, and they have certain supporting functions [1, 2]. Tyloses are the outgrowths of parenchyma cells through vessel-parenchyma pit pairs into the lumen of tracheary elements. They are widely present in many species [3], for example, in genera Quercus and Robinia. Pruning, a viticulture practice to maintain grapevine vigor and health [4], may lead to physical damage to the xylem vessels and tylosis formation in them. The presence of vessel elements, whether partly or completely blocked, can profoundly affect the pattern of water movement within the developing xylem networks [5]. The efficiency of water transportation in the xylem vessels may be influenced by tylosis development and accumulation [4].
Most studies on the tylosis development focused on the plants affected by pathogen infection, insect
1 This text was presented by the authors in English.
Corresponding author. Hua Li. Shaanxi Engineering Research Center for Viti-Viniculture, Yangling 712100, Shaanxi, China. Fax. +86-029-8708-2805; e-mail. lihuawine@nwsuaf.edu.cn
wounding, and environmental stresses [6]. The knowledge of the development and regulation of tyloses in the xylem vessels is limited [7], and the studies on tylosis development in the perennial stems of grapevine and its impact on the vessel water transportation are few as well.
The objectives of this study were to demonstrate the dynamic progress of the tylosis development in the xy-lem parenchyma of grapevine stems and find differences in the wound repair rate in different aged vines on a single shoot. The following experiments were carried out. (1) the investigation of the progress and distribution of tylosis development induced by pruning in xylem tissues and a single vessel; (2) the determination of the tylosis development in xylem tissues of perennial shoots; (3) the observation of the tyloses and xylem structure of the current-year shoots and perennial parts of a grapevine; and (4) the evaluation of the effect of the tylosis development on the vessel water transportation.
MATERIALS AND METHODS
Vineyard. The vineyard was located in Yangling (China, longitude 108°05' E, latitude 34° 16' N) with an altitude of 530 m. The average annual accumulated temperature, sunshine time, and frost-free period are
B
Fig. 1. The sketch of Meili (V vinifera L.) vine shaping in winter of 2009.
Pruning the first shoot of the third nod of arm A, the fourth shoot of arm B, and the seventh shoot of arm C, respectively; the pruning surface was 16 cm apart from the branch.
3400 to 4600°C, 1900 to 2500 h, and 184 to 216 days, respectively. The annual precipitation is 552.6 to 663.9 mm; the soil type is yellow loam.
Xylem structural observations. Sixty three-year-old Meili (Vitis vinifera L.) grapevines were used in this study. The shaping type was a single trunk with three arms (A, B, and C) (fig. 1). The first shoot of the third node of arm A (1), the fourth shoot of arm B (4) and the seventh shoot of arm C (7) were pruned. Pruning surface was 16 cm from the arm. A set of three samples (2 cm length) were taken from the apical side of each pruning surface (number 1, 4, and 7) immediately and named as day 0 samples.
The 2-cm length samples, cut into two 1-cm segments, were placed into a flask and boiled for 4 h [8], sectioned in transverse or radial planes with 20-25 ^m thickness by a sliding microtome (AO-860). Block staining of the botanical materials was carried out using a mixture of Safranin and Fast green FCF [9]. The slices were covered with transparent gum and observed under a light microscope (OLYMPUS bx-51, Japan) with Motic Advanced 3.0 image software for processing the image data. Ten transverse sections of each sample were selected randomly. For each section, length and width of vessel, length-width of vessel-ray pit, and length-width of parenchyma cell-parenchyma cell pit were measured. The length and width of 100 vessels were recorded when perforation plates and pitting types were observed. The terminology describing the secondary xylem and vessel structure in this study was used according to the definitions of the International Association of Wood Anatomists Committee [10].
Tylosis development in vessels. Similarly, other three samples were randomly collected from the apical side of pruning surfaces each day for ten consecutive days. Day 0 to day 10 samples were treated by Jeffrey
resolution method for SEM analysis [11]. Several small stem discs (2-3 mm thick) were cut from the 1-cm segment with a razor blade. These discs were first kept in 4% glutaraldehyde for 12 h and dehydrated successively in a series of glutaraldehyde (30, 50, 70, 80, and 90%) for 20 min and finally in 100% alcohol for 30 min three times. The dehydrated samples were treated by pure isoamyl acetate for 20 min twice and then dried in critical-point dryer (Samdri-780A). The dried samples were coated by Denton Vacuum unit (Cold Sputter-Etch Unit; Denton Vacuum) and observed using an SEM (Hitachi S-3500N; "Hitachi", Japan) at an accelerating voltage of 5 kV.
The area on the section containing 35 to 63 vessels and the xylem region consecutively bounded by rays were chosen randomly for evaluating tylosis development. The vessels were categorized as no tyloses, partially filled with tyloses, and completely occluded with tyloses. The percentages of the vessels with tyloses and those with complete occlusion with tyloses were used to evaluate the tylosis development.
The effect of tyloses on the sap flow in vines. Fifty grapevines in pots with the analogous trunks (including height, diameter, and the number of nodes) and similar growth status of the shoots and crowns were chosen randomly on October 21, 2010. All of the vines were under the Guyot pruning system and for both fruiting arm, there were seven vigorous shoots, numbered 1, 2, 3, 4, 5, 6, and 7 from the trunk to the fruiting arm end. On December 17, 2010, the second and fourth shoots of one fruiting arm (arm A) from the branching sites, as well as the sixth and seventh shoots from another fruiting arm (arm B) were pruned using the same tactics. Meanwhile, the remaining shoots were pruned with one bud left. To determine the sap flow rates, four similar vines were selected in August 30, 2011. On arm A, the sap flow rates of the first and
Table 1. Characteristics of various types of the vessel elements of Meili grapevine (V vinifera L.)
Type of vessel Length, ^m Width, ^m Length and width of vessel-ray pit, ^m Length and width of parenchyma cell-parenchyma cell pit, ^m
With tyloses 441 ± 56 87.3 ± 5.7 8.3 3.7 5.23 3.56
With gels 503 ± 103 63.8 ± 3.4 4.1 3.2 4.87 3.57
Without inclusion 491 ± 98 81.5 ± 5.9 8.9 3.6 5.73 4.01
third shoot were marked as A2 and B2, respectively, while, on arm B, those of the first and third shoots were remarked as A1 and B1, respectively. The sap flow rates were measured continuously for seven days. Water loss (sap flow flux) of the vine was determined by the gravimetric method for seven consecutive days. Pots with the soil and vines were weighed at intervals of one hour. The soil was covered with aluminum foil to eliminate water loss. The sap flow flux of each measured shoot was calculated according to the whole water loss and sap flow rates of each shoot.
The effect of trunk with different cuts on the sap flow of vines. Shoots ofvines in pots with 7-, 8-, and 9-node trunk with similar growth status were selected and pruned, with one single shoot left and used for determining the sap flow rate, marked as A, B, and C, respectively. Water loss (sap flow flux) was determined by the gravimetric method for seven consecutive days. Pots with the soil and vines were weighed continuously every one hour. The soil was covered with aluminum foil to eliminate water loss.
All of the selected vines were covered with a thin film to prevent the evapo
Для дальнейшего прочтения статьи необходимо приобрести полный текст. Статьи высылаются в формате PDF на указанную при оплате почту. Время доставки составляет менее 10 минут. Стоимость одной статьи — 150 рублей.