Handbook of Plant and Crop Physiology

ficiency on plant growth is reduced leaf expansion so that relatively more dry matter is apportioned to the
roots than to the shoots [159]. Phosphorus deficiency in common bean causes substantial reductions in
the shoot-to-root dry weight ratio [148,160] and leaf growth rate, whereas the rate of photosynthesis per
unit leaf area decreased only slightly [161,162]. The slightness of the decrease was attributed to the en-
hancement of the inorganic phosphate (P 1 ) recirculation during glycolic and phosphoenolpyruvate
metabolism. In bean plant tissues, as P 1 concentration decreases, root carbohydrate content [160] and re-
duced pyradine nucleotide concentrations increase [163,164]. These changes are accompanied by a de-
cline in total respiration rate and increased cyanide resistance [165], resulting in a lower concentration of
ATP in the roots [166]. The decrease in P 1 concentration of bean leaves and roots leads to decreased rates
of nitrate uptake and increased nitrate accumulation in roots, accompanied by alterations in nitrate distri-
bution between shoots and roots [167]. Thus, P deficiency not only affects the common bean’s SNF po-
tential [132] but also alters its ability to assimilate and translocate nitrate.
Studies on plant nutrition indicated that plant adaptation to low-P soils is not specific to soil type in
common bean, and that results derived for one soil type may be extrapolated to other soils [150,151].
Mesoamerican and Andean germplasm responded differently to P availability in soil. Mesoamerican
types were more responsive to added P in terms of seed yield. The ability of crop plants to remobilize P
from vegetative to reproductive organs may form an important mechanism that allows plants to improve
the use of P acquired from soil [18,126]. Common bean lines with a low P concentration in shoot tissues
retain more P in roots and older leaves under P-deficient conditions than do lines with a high P concen-
tration [168]. The greater remobilization of P in bean lines with a high P concentration could be attributed
to higher P requirements to maintain normal metabolic activity in growing tissues. Using a split-root sys-
tem and a^32 P tracer, Snapp and Lynch [169] measured patterns of P remobilization from roots and leaves
of common bean and suggested that P retention may allow roots to sustain nutrient and water uptake to
late in the ontogeny.
Lynch and Beebe [148] hypothesized that the existing genetic variation for P efficiency in bean
germplasm, especially variation that is agronomically useful, is largely due to variation in P acquisition
efficiency rather than P use efficiency. Substantial genetic variation in the growth and architecture of bean
root systems was observed, with some evidence that P-efficient genotypes have a vigorous, highly
branched, root system with many growing points [170]. The P status of bean plants greatly influenced lo-
cal root growth patterns and P uptake from localized P patches [171].

ADAPTATION OF BEANS AND FORAGES TO ABIOTIC STRESSES 593

TABLE 1 List of Genotypes and Advanced Breeding Lines of Beans (Phaseolus vulgarisL.) with Superior

Adaptation to Some Abiotic Stresses

Abiotic stress factor Germplasm accessions and advanced lines

AFR 44; AFR 403; BAT 25; BAT 85; Carioca; Diacol Calima; MUS 97; PAI

112; PEF 4; PEF 16; Porrillo Sintetico; RAO 55

A 321; ACC 433; AFR 300; AFR 475; AFR 544; BAT 85; BAT 477; Carioca;

DOR 375; G 1937; G 3153; G 5053; G 7300; G 11702; G 12105; G 16106;

G 19842; G 21212; MMS 224; MUS 18; PAI 112; PEF 14; RWR 382, VAX

1; XAN 76

DOR 375; EMP 84; ICA Pijao; MUS 97; Porrillo Sintetico; RAO 52; XAN 76

7/4 ACC; AFR 300; AFR 344; AFR 476; AND 740; AND 773; CAL 98; F-15;

FEB 190; FEB 192; Muhinga; MUS 18; Ntekerabasilumu; RAB 94; RAB

475; RAO 55; Superba

A 120; A 197; AFR 13; AFR 298; AFR 378; AFR 476; AFR 531; AFR 544;

AND 829; AND 871; Argentino; BAT 271; Calima; EMP-84; H6 Mulatinho;

CAL 96; Carioca; DOR 404; MCM 5001; NEPA 29; NEPA 38; PAD 126;

Pintado; PVA 774; SUG 69; XAN 76

Carioca; G 12871; G 21212; XAN 76; RAO 55; OBA 1

A 54; A 170; A 195; Apetito; BAT 336; BAT 477; BAT 1289; Bayo Criollo del

Llano; Bayo Rio Grande; Durango 5; Durango 222; Favinha; Gordo; Guana-

juato 31; Mulatinho Vagem Roxa; Rim do Porco; San Cristobal 83; SEA 5;

V 8025

Low-N tolerance

Low-P tolerance

Low-K tolerance

Al tolerance

Mn tolerance

Low-soil-fertility tolerance

Drought

Source: Adapted from Refs. 95, 108, 119, 121, 131, and 148.