DOI: 10.5061/dryad.66th54k
title: Data from: Disentangling evolutionary, environmental and morphological drivers of plant anatomical adaptations to drought and cold in Himalayan graminoids

description: Understanding what determine plants ability to survive drought and cold is
 crucial for predicting how plants may respond to ongoing climate change.
 Plant survival strategies are usually characterized by morphological and
 physiological adaptations, while their underlying anatomical settings are
 largely unknown. Woody angiosperms and herbaceous dicots have repeatedly
 evolved small water transporting conduits and large storage parenchyma
 tissues at colder or drier places to cope with freezing- and
 drought-induced damages. However, whether these adaptations are also valid
 for graminoids remains unclear. Here we show that stem anatomical
 variations in grasses, sedges and rushes dominating in western Himalayan
 grasslands are driven by elevation and soil moisture via control over
 aboveground plant stature and belowground clonal growth, while
 phylogenetic constraints have only a weak effect. Phylogenetic comparative
 analyses controlling for confounding factors showed that the
 elevation-related cooling controls the conductive system through reduced
 vessel diameter and extended assimilatory and storage tissues with more
 chlorenchyma and less sclerenchyma around vessels. The soil moisture
 deficit, on the other hand, determines stabilization structures by
 promoting short-rhizomatous turf graminoids with hollow stems, thicker
 epidermis and deep adventitious roots in dry steppes and semi-deserts.
 Saline wetlands and moist alpine pastures promote long-rhizomatous
 short-stature plants with lower need for mechanical support (absence of
 hollow stem) and exposure to high evaporative forcing (thinner epidermis).
 Observed trends of decreasing vessel sizes and lignification rate with
 elevation supports the existing knowledge that narrower vessels and
 extensive parenchyma assist plants to grow in cold environments by
 avoiding freezing-induced cavitation. Our results bring novel information
 on ecological drivers influencing the evolution of anatomical adaptations
 in high mountain graminoids. Distinct grassland types, covering elevations
 from 2650 to 6150 m, harbor unrelated species with different evolutionary
 histories that have converged towards similar anatomical structures.
description: OIK-06451.R2
 dataBaseline anatomical data
 of characteristic features on stem cross-section of primarily Cyperaceae
 and Poaceae. The features are defined by the outline of the stem (culm),
 the structure of the epidermis, the arrangement of vascular bundles, the
 form and size of chlorenchyma (assimilatory tissue), the peripheral
 sclerenchymatic belt, the sclerenchymatic girders, the sclerenchymatic
 sheath around vascular bundles and cavities (intercellulars) in the
 parenchymatic tissues and vessel size and the presence of cavities in the
 protophloem of vascular bundles. The following features are principally
 based on Metcalfe C R. 1960 Anatomy of the Monocotyledons l. Gramineae.
 Oxford Clarendron Press. 731 pg; and Metcalfe C R. 1971. Anatomy of the
 Monocotyledons V Cyperaceae. Oxford Clarendron Press. 597
 pg.