Ecological significance of wood anatomy in two lianas from arid southwestern Saudi Arabia

Abstract

The hot and arid lowlands of southwestern Saudi Arabia are home to two common lianas, Cocculus pendulus and Leptadenia arborea. This paper attempts to relate the adaptation of these two climbing woody perennials to such a harsh environment to the anatomy and hydraulic characteristics of their wood. The stems of these lianas have wood with wide xylem vessels and high hydraulic conductivity which should enhance water flow to the upper canopy despite their severe twisting. Hydraulic conductivity is further helped by the simple perforation plates of xylem vessels. The circular thickening of xylem walls gives them strength and reduces the risk of their collapse and the ensuing embolism in the advent of high tension created by severe water deficit and high evapo-transpiration demand. Wide vessels, on the other hand, are more susceptible to embolism. This problem may be overcome by reducing the solute potential of xylem sap by hydrolysis of starch grains which were found to be abundant in the vicinity of the vessels. This should help absorb water by the deep roots from the capillary fringes of the typically shallow water table in this particular habitat. Furthermore, the abundance of ray parenchyma cells between xylem groups of both lianas provides great flexibility with minimum damage to water conduits in the stem during climbing and twisted growth. It was concluded that these wood features in both lianas are crucial for survival under the harsh conditions of arid Tihama plains of southwestern Saudi Arabia.

Xylem cavitation susceptibility and refilling mechanisms in olive trees infected by Xylella fastidiosa

“…Several studies have documented a dense accumulation of starch grains in the vessel’s cells as an integral part of embolism recovery: Masrahi et al . 43 observed in xylem parenchima of the two lianas Cocculus pendulus and Leptadenia arborea a great quantity of starch grains that can reduce the solute potential of xylem sap improving the upward flow of water, this proposed strategy could help plants to repair air filled vessels and to survive in the water deficit of their severe habitat. Starch granules are readily apparent in the fibers of grapevine xylem and it was proposed that they generated an osmotic driving force for refilling 38 .…”

Mechanisms for minimizing height‐related stomatal conductance declines in tall vines

“…Despite observations of steep declines in gas exchange rates with height in trees (Delzon, Sartore, Burlett, Dewar, & Loustau, ; Fang et al, ; Magnani et al, ; McDowell et al, ; Renninger, Phillips, & Hodel, ; Schäfer et al, ), studies in woody vines (Chen et al, ; Masrahi, ; Taneda & Tateno, ; Zhu & Cao, ) show that g s remains high along the stem. Our results agree with these latter observations.…”

“…This implies that vines must have mechanisms compensating for hydraulic limitations, imposed by extended path length and increased leaf size with height (Figure ). Proposed mechanisms for increasing hydraulic flow in vine species include deeper rooting systems (Chen et al, ), increased stem hydraulic conductivity and water storage (Gartner, ; Johnson et al, ), increased size and number of vessels (Masrahi, ; Rosell & Olson, ), and segmentation of hydraulic resistance (Taneda & Tateno, ).…”

“…Proposed mechanisms for increasing hydraulic flow in vine species include deeper rooting systems (Chen et al, 2015), increased stem hydraulic conductivity and water storage (Gartner, 1991;Johnson et al, 2013), increased size and number of vessels (Masrahi, 2014;Rosell & Olson, 2014), and segmentation of hydraulic resistance (Taneda & Tateno, 2011).…”

Plasticidade de árvores de <i>Eucalyptus grandis</i> no contexto das mudanças climáticas: interação do déficit hídrico e da fertilização no crescimento e qualidade do lenho das árvores

“…cavitação é considerada um dos principais fatores que levam a redução da produtividade das árvores, podendo ocasionar a morte da planta durante um período de seca(MCDOWEL et al, 2008). Nesta situação, há uma redução do fornecimento de água para as folhas, acarretando o decréscimo do potencial hídrico(MASRAHI, 2014). Na sequência, há um desencadeamento de embolia; o embolismo espalha-se de elemento para elemento por meio das placas de perfuração até que todo vaso torna-se inutilizável para transporteSPERRY, 2001).…”