Best of Both Worlds: Simultaneous High-Light and Shade-Tolerance Adaptations within Individual Leaves of the Living Stone Lithops aucampiae

Abstract

“Living stones” (Lithops spp.) display some of the most extreme morphological and physiological adaptations in the plant kingdom to tolerate the xeric environments in which they grow. The physiological mechanisms that optimise the photosynthetic processes of Lithops spp. while minimising transpirational water loss in both above- and below-ground tissues remain unclear. Our experiments have shown unique simultaneous high-light and shade-tolerant adaptations within individual leaves of Lithops aucampiae. Leaf windows on the upper surfaces of the plant allow sunlight to penetrate to photosynthetic tissues within while sunlight-blocking flavonoid accumulation limits incoming solar radiation and aids screening of harmful UV radiation. Increased concentration of chlorophyll a and greater chlorophyll a∶b in above-ground regions of leaves enable maximum photosynthetic use of incoming light, while inverted conical epidermal cells, increased chlorophyll b, and reduced chlorophyll a∶b ensure maximum absorption and use of low light levels within the below-ground region of the leaf. High NPQ capacity affords physiological flexibility under variable natural light conditions. Our findings demonstrate unprecedented physiological flexibility in a xerophyte and further our understanding of plant responses and adaptations to extreme environments.

Photosynthetic Response of Soybean Leaf to Wide Light-Fluctuation in Maize-Soybean Intercropping System

“…Leaf photosynthetic rate is related to chlorophyll content ( Shao et al, 2014 ). Chl a is essential for determining photosynthesis, and Chl b determine the wavelengths of light that can be absorbed by the organism ( Field et al, 2013 ). Intercropped soybean leaf contained more chl a and chl b content per weight and had lower chl a/b than those in monocropping, which could broaden the wavelengths of light that could be absorbed, and effectively increase the ability of light capture ( Gong et al, 2014 ).…”

The Optical Properties of Leaf Structural Elements and Their Contribution to Photosynthetic Performance and Photoprotection

“…Species with large windows thrive in cloudy, high-rainfall regions, whereas species thriving in high solar irradiance regions have small windows, minimizing the probability of photo-inhibition [ 52 ]. Moreover, Lithops plants have sufficient biochemical flexibility to respond to variable light conditions within the same leaf (extreme high light intensity in the above ground region and moderate or low intensity in the below ground) [ 58 , 59 ].…”

“…Microscopic observations confirmed that the spatial distribution of the CaCIs is compatible with their proposed optical function [ 94 ]. Moreover, CaOx crystals within the epidermis of Lithops aucampiae leaves may scatter light within the below-ground region of the leaves, thus enriching the lower tissues with photons [ 59 ]. It was also proposed that in some species thriving in extreme environments, crystal sand may provide protection against photo-inhibition by filtering and dispersing the solar irradiance and moderating the internal leaf temperature [ 104 ].…”

Light‐Guiding Biomaterials for Biomedical Applications

“…(b) Lithops olivacea with green bodies and large pinkish translucent windows through which sunlight penetrate into the leaf. [9] (c) Fenestrated Haworthia and Lithops with translucent tissues. [89] (d) Optical images of red laser light guided in (left) in a corn root and (right) in an oat seedling.…”

“…This arrangement ensures high photosynthesis yield while avoiding localized absorption at the top of the leaves, which can cause photothermal damage during hot, dry days. [9]…”